Emergency contraception: Difference between revisions

Emergency contraception
Emergency contraception
Background
Type	Hormonal (progestin or others) or intra-uterine
First use	1970s
Failure rates (per use)
Perfect use	ECP: see article text; IUD: under 1%
Typical use	89%, 74%, 47%, 53%, or 83% (please see Effectiveness of ECPs below)%
Usage
User reminders	Pregnancy test required if no period seen after 3 weeks
Clinic review	Recommended to consider need screen STDs or consider ongoing routine contraceptive options
Advantages and disadvantages
STI protection	No
Periods	ECP may disrupt next menstrual period by couple days. IUDs may make menstruation heavier and more painful
Benefits	IUDs may be subsequently left in place for ongoing contraception
Risks	As per methods
Medical notes
	Combined estrogrogen/progestin pills of Yuzpe regimen now superseded by better-tolerated and more effective progestin-only pill.; Progestin only ECP licensed for use within 3 days of unprotected intercourse, Ulipristal acetate and IUDs within 5 days.

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Revision as of 19:16, 21 October 2012

Emergency contraception (EC), or emergency postcoital contraception, are birth control measures that, if taken after sexual intercourse, may prevent pregnancy.

Forms of EC include:

Emergency contraceptive pills (ECPs)—sometimes simply referred to as emergency contraceptives (ECs) or the "morning-after pill"—are drugs intended to disrupt ovulation or fertilization, which are steps necessary for pregnancy (contraceptives).^[1]^[2]^[3]
Intrauterine devices (IUDs)—usually used as a primary contraceptive method, but sometimes used as emergency contraception.^[3]

Emergency contraceptive pills (ECPs)

Emergency contraceptive pills (sometimes referred to as emergency hormonal contraception (EHC) in Great Britain) may contain higher doses of the same hormones (estrogens, progestins, or both) found in regular combined oral contraceptive pills. Taken after unprotected sexual intercourse or contraceptive failure, such higher doses may prevent pregnancy from occurring.^[4]

The phrase "morning-after pill" is a misnomer; ECPs are most effective when used shortly after intercourse.

Types of ECPs

The progestin-only method uses the progestin levonorgestrel in a dose of 1.5 mg, either as two 750 μg doses 12 hours apart, or more recently as a single dose. Progestin-only EC is available as a dedicated emergency contraceptive product under many names worldwide, including: in the U.S., Canada and Honduras as Plan B; in Great Britain, Ireland, Australia, New Zealand, Portugal and Italy as Levonelle; in South Africa as Escapelle; in 44 nations including France, most of Western Europe, India, and several countries in Africa, Asia and Latin America as NorLevo; and in 44 nations including most of Eastern Europe, Mexico and many other Latin American countries, Portugal, Australia and New Zealand, Israel, China, Hong Kong, Taiwan and Singapore as Postinor-2.^[5] This pill typically works up to 72 hours after intercourse.^[6]

The combined or Yuzpe regimen uses large doses of both estrogen and progestin, taken as two doses at a 12-hour interval. This method is now believed to be less effective and less well tolerated than the progestin-only method. ^[7] It is possible to obtain the same dosage of hormones, and therefore the same effect, by taking several regular combined oral contraceptive pills. For example, 4 Ovral pills are the same as 4 Preven pills.^[8]^[9] The United States Food and Drug Administration (FDA) approved this off-label use of certain brands of regular combined oral contraceptive pills in 1997.^[4]^[8]^[10]

Ulipristal acetate (known as ella in the US and Ellaone in Europe) was approved as an ECP in Europe in early 2009 and in the US in August 2010. It works for up to 120 hours after intercourse.^[6] It prevents pregnancy by delaying or inhibiting ovulation and inhibiting follicle rupture.^[11] Watson Pharmaceuticals announced the availability of ella in the United States on December 1, 2010, in retail pharmacies, clinics and one online pharmacy, KwikMed.^[12]

Emergency contraceptive pills (ECPs) are not to be confused with mifepristone (RU486, Mifeprex), which is used as an "abortion pill". The term "emergency contraceptive pill" does not refer to mifespristone, which is most commonly used in 200 or 600 mg doses as an abortifacient.^[13] However, in China and Russia only,^[11] mifepristone is available as either emergency contraception or as an abortifacient, depending on whether it is used before or after implantation. If used as emergency contraception, a low dose of mifepristone is slightly less effective than higher doses, but has fewer side effects.^[14] As of 2000^[update], the smallest dose available in the USA was 200 mg.^[15] Mifepristone, however, is not approved for emergency contraceptive use in the United States.^[16] A review of studies in humans concluded that the contraceptive effects of the 10 mg dose are due to its effects on ovulation,^[17] but understanding of its mechanism of action remains incomplete. Higher doses of mifepristone can disrupt implantation and, unlike levonorgestrel, mifepristone can be effective in terminating established pregnancies.

Effectiveness of ECPs

The effectiveness of emergency contraception is presented differently from the effectiveness of ongoing methods of birth control: it is expressed as a percentage reduction in pregnancy rate for a single use of EC. Different ECP regimens have different effectiveness levels, and even for a single regimen different studies may find varying rates of effectiveness. Using an example of "75% effective", an article in American Family Physician explains the effectiveness calculation thus:

... these numbers do not translate into a pregnancy rate of 25 percent. Rather, they mean that if 1,000 women have unprotected intercourse in the middle two weeks of their menstrual cycles, approximately 80 will become pregnant. Use of emergency contraceptive pills would reduce this number by 75 percent, to 20 women.^[18]

The progestin-only regimen (using levonorgestrel) is reported by the U.S. FDA to have an 89% effectiveness. As of 2006^[update], the labeling on the U.S. brand Plan B explained this effectiveness rate by stating, "Seven out of every eight women who would have gotten pregnant will not become pregnant."^[19]

In 1999, a meta-analysis of eight studies of the combined (Yuzpe) regimen concluded that the best point estimate of effectiveness was 74%.^[20] A 2003 analysis of two of the largest combined (Yuzpe) regimen studies, using a different calculation method, found effectiveness estimates of 47% and 53%.^[21]

For both the progestin-only and Yuzpe regimens, the effectiveness of emergency contraception is highest when taken within 12 hours of intercourse and declines over time.^[7]^[22]^[23] While most studies of emergency contraception have only enrolled women within 72 hours of unprotected intercourse, a 2002 study by the World Health Organization (WHO) suggested that reasonable effectiveness may continue for up to 120 hours (5 days) after intercourse.^[24]

For 10 mg of mifepristone taken up to 120 hours (5 days) after intercourse, the combined estimate from three trials was an effectiveness of 83%.^[25] A review found that many trials found a regimen of 25–50 mg of mifepristone to have higher effectiveness. However, when reviewers looked at only high-quality trials, the difference in effectiveness was not statistically significant.^[26]

History of calculation methods

Early studies of emergency contraceptives did not attempt to calculate a failure rate; they simply reported the number of women who became pregnant after using an emergency contraceptive. Since 1980, clinical trials of emergency contraception have first calculated probable pregnancies in the study group if no treatment were given. The effectiveness is calculated by dividing observed pregnancies by the estimated number of pregnancies without treatment.^[27]

Placebo-controlled trials that could give a precise measure of the pregnancy rate without treatment would be unethical, so the effectiveness percentage is based on estimated pregnancy rates. These are currently estimated using variants of the calendar method.^[28] Women with irregular cycles for any reason (including recent hormone use such as oral contraceptives and breastfeeding) must be excluded from such calculations. Even for women included in the calculation, the limitations of calendar methods of fertility determination have long been recognized. In their April 2012 emergency review article, Trussell and Raymond note:

Calculation of effectiveness, and particularly the denominator of the fraction, involves many assumptions that are difficult to validate...The risk of pregnancy for women requesting ECPs appears to be lower than assumed in the estimates of ECP efficacy, which are consequently likely to be overestimates. Yet, precise estimates of efficacy may not be highly relevant to many women who have had unprotected intercourse, since ECPs are often the only available treatment.^[29]

In 1999, hormonal assay was suggested as a more accurate method of estimating fertility for EC studies.^[30]

Safety

Existing pregnancy is not a contraindication in terms of safety, as there is no known harm to the woman, the course of her pregnancy, or the fetus if progestin-only or combined emergency contraception pills are accidentally used, but EC is not indicated for a woman with a known or suspected pregnancy because it is not effective in women who are already pregnant.^[29]^[31]^[32]^[33]^[34]^[35]^[36]^[37]^[38]

The World Health Organization (WHO) lists no medical condition for which the risks of emergency contraceptive pills outweigh the benefits.^[35] The American Academy of Pediatrics (AAP) and experts on emergency contraception have concluded that progestin-only ECPs may be preferable to combined ECPs containing estrogen in women with a history of blood clots, stroke, or migraine.^[29]^[31]^[32]

The AAP, American College of Obstetricians and Gynecologists (ACOG), U.S. Food and Drug Administration, WHO, Royal College of Obstetricians and Gynaecologists, and other experts on emergency contraception state that there are no medical conditions in which progestin-only ECPs are contraindicated.^[29]^[31]^[32]^[33]^[34]^[35]^[36] RCOG specifically note current venous thromboembolism, current or past history of breast cancer, inflammatory bowel disease, and acute intermittent porphyria as conditions where the advantages of using emergency contraceptive pills generally outweigh the theoretical or proven risks.^[36]

The herbal preparation of St John's wort and some enzyme-inducing drugs (e.g. anticonvulsants or rifampicin) may reduce the effectiveness of ECP, and a larger dose may be required.^[39]^[40]

The AAP, ACOG, FDA, WHO, RCOG, and experts on emergency contraception have concluded that ECPs, like all other contraceptives, reduce the absolute risk of ectopic pregnancy by preventing pregnancies, and that the best available evidence, obtained from over 7,800 women in randomized controlled trials, indicates there is no increase in the relative risk of ectopic pregnancy in women who become pregnant after using progestin-only ECPs.^[3]^[29]^[31]^[32]^[33]^[34]^[35]^[36]^[38]^[39]^[41]^[42]^[43]

Side effects

The most common side effect reported by users of emergency contraceptive pills was nausea (50.5% of 979 Yuzpe regimen users and 23.1% of 977 levonorgestrel-only users in the 1998 WHO trial; 14.3% of 2,720 levonorgestrel-only users in the 2002 WHO trial); vomiting is much less common and unusual with levonorgestrel-only ECPs (18.8% of 979 Yuzpe regimen users and 5.6% of levonorgestrel-only users in the 1998 WHO trial; 1.4% of 2,720 levonorgestrel-only users in the 2002 WHO trial).^[7]^[24]^[39] Anti-emetics are not routinely recommended with levonorgestrel-only ECPs.^[39]^[44] If a woman vomits within 2 hours of taking a levonorgestrel-only ECP, she should take a further dose as soon as possible.^[39]^[45]

Other common side effects (each reported by less than 20% of levonorgestrel-only users in both the 1998 and 2002 WHO trials) were abdominal pain, fatigue, headache, dizziness, and breast tenderness.^[7]^[24]^[39] Side effects usually do not occur for more than a few days after treatment, and they generally resolve within 24 hours.^[29]

Temporary disruption of the menstrual cycle is also commonly experienced. If taken before ovulation, the high doses of progestogen in levonorgestrel treatments may induce progestogen withdrawal bleeding a few days after the pills are taken. One study found that about half of women who used levonorgestrel ECPs experienced bleeding within 7 days of taking the pills.^[46] If levonorgestrel is taken after ovulation, it may increase the length of the luteal phase, thus delaying menstruation by a few days.^[47] Mifepristone, if taken before ovulation, may delay ovulation by 3–4 days.^[48] (Delayed ovulation may result in a delayed menstruation.) These disruptions only occur in the cycle in which ECPs were taken; subsequent cycle length is not significantly affected.^[46] If a woman's menstrual period is delayed by two weeks or more, it is advised that she take a pregnancy test.^[33] (Earlier testing may not give accurate results.)

Availability by country

Intrauterine device (IUD) for emergency contraception

An alternative to emergency contraceptive pills is the copper-T intrauterine device (IUD) which can be used up to 5 days after unprotected intercourse to prevent pregnancy. Insertion of an IUD is more effective than use of Emergency Contraceptive Pills - pregnancy rates when used as emergency contraception are the same as with normal IUD use. IUDs may be left in place following the subsequent menstruation to provide ongoing contraception (3–10 years depending upon type).^[49]

Postcoital high-dose progestin-only oral contraceptive pills as ongoing contraception

One brand of levonorgestrel pills, Postinor, was marketed as an ongoing method of postcoital contraception.^[50] However, there are serious drawbacks to such use of postcoital high-dose progestin-only oral contraceptive pills, especially if they are not used according to their package directions, but are instead used according to the package directions of emergency contraceptive pills:

Due to the increasing severity of side effects with frequent use, Postinor is only recommended for women who have intercourse four or fewer times per month.^[50]^[51]
If not used according to their package directions, but instead used according to the directions of levonorgestrel emergency contraceptive pills (up to 72 hours after intercourse), they would be estimated to have a "perfect-use" (when not used according to their package directions but used as directed on the package directions for levonorgestrel emergency contraception pills) pregnancy rate of 20% per year when used as the sole means of contraception (as compared to a 40% annual pregnancy rate for the Yuzpe regimen).^[52] These failure rates would be higher than those of almost all other birth control methods, including the rhythm method and withdrawal.^[53]
Like all hormonal methods, postcoital high-dose progestin-only oral contraceptive pills do not protect against sexually transmitted infections.^[54]

ECPs are generally recommended for backup or "emergency" use, rather than as the primary means of contraception. They are intended for use when other means of contraception have failed—for example, if a woman has forgotten to take a birth control pill or when a condom is torn during sex.^[52]

History

The use of synthetic estrogens as a post coital contraceptive was discovered by Dr. John McLean Morris in 1966.^[55]^[56] A few different drugs were studied, with a focus on high-dose estrogens, and it was originally hoped that postcoital contraception would prove viable as an ongoing contraceptive method.^[57]

The first widely used methods were five-day treatments with high-dose estrogens, using diethylstilbestrol (DES) in the US and ethinyl estradiol in the Netherlands.^[58]^[59]

In the early 1970s, the Yuzpe regimen was developed by A. Albert Yuzpe in 1974;^[60] progestin-only postcoital contraception was investigated (1975);^[61] and the copper IUD was first studied for use as emergency contraception (1975).^[62] Danazol was tested in the early 1980s in the hopes that it would have fewer side effects than Yuzpe, but was found to be ineffective.^[63]

The Yuzpe regimen became the standard course of treatment for postcoital contraception in many countries in the 1980s. The first prescription-only combined estrogen-progestin dedicated product, Schering PC4 (ethinylestradiol and norgestrel), was approved in the UK in January 1984 and first marketed in October 1984.^[64] Schering introduced a second prescription-only combined product, Tetragynon (ethinylestradiol and levonorgestrel) in Germany in 1985.[1] By 1997, Schering AG dedicated prescription-only combined products had been approved in only 9 countries: the UK (Schering PC4), New Zealand (Schering PC4), South Africa (E-Gen-C), Germany (Tetragynon), Switzerland (Tetragynon), Denmark (Tetragynon), Norway (Tetragynon), Sweden (Tetragynon) and Finland (Neoprimavlar); and had been withdrawn from marketing in New Zealand in 1997 to prevent it being sold over-the-counter.[2][3][4] Regular combined oral contraceptive pills (which were less expensive and more widely available) were more commonly used for the Yuzpe regimen even in countries where dedicated products were available.^[65]

Over time, interest in progestin-only treatments increased. The Special Program on Human Reproduction (HRP), an international organization whose members include the World Bank and World Health Organization, "played a pioneering role in emergency contraception" by "confirming the effectiveness of levonorgestrel."^[66] After the WHO conducted a large trial comparing Yuzpe and levonorgestrel in 1998,^[67]^[68] combined estrogen-progestin products were gradually withdrawn from some markets (Preven in the United States discontinued May 2004, Schering PC4 in the UK discontinued October 2001, and Tetragynon in France) in favor of progestin-only EC, although prescription-only dedicated Yuzpe regimen products are still available in some countries.

In 2002, China became the first country in which mifepristone was registered for use as EC.

In 2012, DrEd.com, an online doctors practice, launched an emergency-contraception-by-courier service^[69] across London. DrEd anticipates the service will be attractive to women that don’t have time to go to a pharmacy or their GP for the prescription, and by those too embarrassed to request emergency contraception face-to-face.^[70]

United States & Canada

DES
- In 1971, a New England Journal of Medicine editorial calling attention to previously published studies on the use of DES as a postcoital contraceptive at Yale University, and a large study published in JAMA on the use of DES as a postcoital contraceptive at the University of Michigan, led to off-label use of DES as a postcoital contraceptive becoming prevalent at many university health services.^[71]^[72]
- In May 1973, in an attempt to restrict off-label use of DES as a postcoital contraceptive to emergency situations such as rape, a FDA Drug Bulletin was sent to all U.S. physicians and pharmacists that said the FDA had approved, under restricted conditions, postcoital contraceptive use of DES.^[73] (In February 1975, the FDA Commissioner testified that the only error in the May 1973 FDA Drug Bulletin was that the FDA had not approved postcoital contraceptive use of DES.)^[74]
- In September 1973, the FDA published a proposed rule specifying patient labeling and special packaging requirements for any manufacturer seeking FDA approval to market DES as a postcoital contraceptive, inviting manufacturers to submit abbreviated new drug applications (ANDAs) for that indication, and notifying manufacturers that the FDA intended to order the withdrawal of DES 25 mg tablets (which were being used off-label as postcoital contraceptives).^[75]^[76]^[76]^[77]
- In late 1973, Eli Lilly, the largest U.S. manufacturer of DES, discontinued its DES 25 mg tablets and in March 1974 sent a letter to all U.S. physicians and pharmacists telling them it did not recommend use of DES as a postcoital contraceptive.^[74]
- Only one pharmaceutical company, Tablicaps, Inc., a small manufacturer of generic drugs, ever submitted (in January 1974) an ANDA for use of DES as an emergency postcoital contraceptive, and the FDA never approved it.^[74]^[78]
- In February 1975, the FDA said it had not yet approved DES as a postcoital contraceptive, but would after March 8, 1975 permit marketing of DES for that indication in emergency situations such as rape or incest if a manufacturer obtained an approved ANDA that provided patient labeling and special packaging as set out in a FDA final rule published in February 1975.^[79] To discourage off-label use of DES as a postcoital contraceptive, in February 1975 the FDA ordered DES 25 mg (and higher) tablets removed from the market and ordered the labeling of lower doses (5 mg and lower) of DES still approved for other indications be changed to state: "THIS DRUG PRODUCT SHOULD NOT BE USED AS A POSTCOITAL CONTRACEPTIVE" in block capital letters on the first line of the physician prescribing information package insert and in a prominent and conspicuous location of the container and carton label.^[76]^[80]
- In March 1978, a FDA Drug Bulletin was sent to all U.S. physicians and pharmacists which said: "FDA has not yet given approval for any manufacturer to market DES as a postcoital contraceptive. The Agency, however, will approve this indication for emergency situations such as rape or incest if a manufacturer provides patient labeling and special packaging. To discourage 'morning after' use of DES without patient labeling, FDA has removed from the market the 25 mg tablets of DES, formerly used for this purpose."^[81]
- In the 1980s, off-label use of the Yuzpe regimen superseded off-label use of DES for postcoital contraception.^[78]^[82]^[83]
- DES is no longer commercially available in the U.S.; Eli Lilly, the last U.S. manufacturer, ceased production in spring 1997.^[84]

Yuzpe regimen & Preven
- On February 25, 1997, the FDA posted a notice in the Federal Register saying it had concluded that the Yuzpe regimen was safe and effective for off-label use as postcoital EC, was prepared to accept NDAs for COCPs labeled as ECPs, and listed 6 then available COCPs (there are now 22) that could be used as ECPs.^[8]^[85]
- On September 1, 1998, the FDA approved the prescription Yuzpe regimen Preven Emergency Contraception Kit (which contained a urine pregnancy test and 4 COCPs).^[86] Preven was discontinued in May 2004.^[87]

Plan B
- On July 28, 1999, the FDA approved the prescription progestin-only Plan B (two 750 µg levonorgestrel pills) emergency contraceptive.^[88]
- On August 24, 2006, the FDA approved nonprescription behind-the-counter access to Plan B from pharmacies staffed by a licensed pharmacist for women 18 or older; a prescription-only form of Plan B was made available for younger females aged 17 and younger.^[89]
- On November 6, 2006, Barr Pharmaceuticals announced that its subsidiary, Duramed Pharmaceuticals, had initiated shipment of dual-label Plan B OTC/Rx and it would be available in pharmacies across the U.S. by mid-November 2006.^[90]
- On March 23, 2009, a US judge ordered the FDA to allow 17 year olds to acquire Plan B without a prescription.^[91] This now changes the August 24, 2006 ruling and Plan B is now available "behind the counter" for men and women. There is a prescription method available for girls under 17.

International Consortium for Emergency Contraception

In 1995, the Rockefeller Foundation convened a meeting to discuss emergency contraception. After the meeting, a group of seven international organizations formed The International Consortium for Emergency Contraception (ICEC) to promote EC as a part of mainstream reproductive health care worldwide.^[92] Dedicated products for EC were "virtually unknown" in 1995, there was little awareness of EC as an option, and EC was not used as public health measure.^[93]

The seven founding member organizations were the Concept Foundation, the International Planned Parenthood Federation (IPPF), the Pacific Institute for Women's Health, the World Health Organization (WHO), the Population Council, Population Services International, and the Program for Appropriate Technology in Health (PATH).^[92]

The Concept Foundation is the distribution arm of ICEC; its funding for the development of Postinor-2 came from the Rockefeller Foundation and the David and Lucile Packard Foundation, as well as the other ICEC organizations.^[94]

The Consortium helped promote the availability of EC by:^[93]

Manufacturing an EC product. The ICEC worked with the Hungarian pharmaceutical firm Gedeon Richter to repackage its contraceptive Postinor as an emergency contraceptive, called Postinor-2. Distributing Postinor-2, principally in developing countries, was the primary work of the ICEC.
Facilitating product registration in two ways. First, the ICEC encouraged interest in EC products through meetings with public-sector agencies and non-governmental organizations (NGOs) who they perceived would benefit from adding EC to the products they distribute. Second, by helping organizations applying for EC registration through the country-specific approval process, including lobbying of local leaders who may be influential in the registration decision.
Negtiotiating a public-sector price. The ICEC's agreement with Gedeon Richter provided a discount price at which EC could be obtained by public-sector agencies in developing countries.
Marketing and social marketing.

An ICEC member organization, the International Planned Parenthood Federation (IPPF), has launched its own dedicated levonorgestrel EC product, Optinor.^[95]

Relationship to high risk sex and abortion

The current (October 2005) AAP Policy Statement on Emergency Contraception states: "The concern that widespread emergency contraception use would encourage unprotected coitus in teens is not supported in the literature."^[31]

The latest (April 2012) review by emergency contraception experts Trussell and Raymond ^[29] states: "Reported evidence would seem to demonstrate convincingly that making ECPs more widely available does not increase risk-taking or adversely affect regular contraceptive use.^[96]^[97]^[98]^[99]^[100]^[101]^[102]^[103]^[104]^[105]^[106] and that women who are the most diligent about ongoing contraceptive use are those most likely to seek emergency treatment."^[107]

In France, Sweden, and Britain—where Yuzpe-regimen EC had been available by prescription for more than a decade and progestin-only EC has been available without a prescription for 8, 6, and 2 years respectively—the abortion rate was stable or higher during that time period.^[108] Another study concluded that distribution of free, advance supplies of EC to large numbers of women in Scotland did not reduce abortion rates.^[109] A randomized controlled trial of 2000 women in China compared women with advance access to EC to women without access, and noted that the pregnancy rate was the same between the two groups. The study observed that "...providing EC in advance increases use, but there is no direct evidence that it reduces unintended pregnancy" and concluded that EC may not lower abortion rates.^[110]

In September 2006, emergency contraception expert Anna Glasier wrote a BMJ editorial entitled "Emergency Contraception. Is it worth all the fuss?" that said in closing: "So is emergency contraception worth the fuss? If you are a woman who has had unprotected sex then of course it is, because emergency contraception will prevent pregnancy in some women some of the time—and if you don’t want to get pregnant anything is better than nothing. If you are the CMAJ’s editor or FDA commissioner then yes, because scientific freedom is worth the fight. If you are looking for an intervention that will reduce abortion rates, emergency contraception may not be the solution, and perhaps you should concentrate most on encouraging people to use contraception before or during sex, not after it."^[111]

EC and sexual assault

Before EC was used in the general population or defined as "emergency contraception," it was used, beginning in the 1960s and 70s, specifically as a treatment for victims of sexual assault.^[112]^[113] Pregnancy rates among rape victims of child-bearing age are around 5%; in the U.S., about half of rape victims who become pregnant have abortions.^[114] Although EC is commonly used as an option for victims of sexual assault, some researchers believe such use is a public health measure that is not sufficiently widespread.^[115]

Mechanism of action

The primary mechanism of action of combined estrogen-progestogen emergency contraceptive pills is to prevent fertilization by inhibition of ovulation.^[3]

The primary mechanism of action of progestogen-only emergency contraceptive pills is to prevent fertilization by inhibition of ovulation.^[3]^[39]^[42]^[116]^[117]^[118] The best available evidence is that they do not have any post-fertilization effects such as the prevention of implantation.^[3]^[39]^[42]^[116]^[117]^[118] The European EMA-approved labels and the U.S. FDA-approved labels for levonorgestrel emergency contraceptive pills (based on labels for regular oral contraceptive pills) both say they may cause endometrial changes that discourage implantation.^[119]^[120]^[121] Daily use of regular oral contraceptive pills can alter the endometrium (although this has not been proven to interfere with implantation), but the isolated use of a levonorgestrel emergency contraceptive pill does not have time to alter the endometrium.^[119] In March 2011, the International Federation of Gynecology and Obstetrics (FIGO) issued a statement that: "review of the evidence suggests that LNG [levonorgestreol] ECPs cannot prevent implantation of a fertilized egg. Language on implantation should not be included in LNG ECP product labeling."^[119]^[122] In June 2012, a New York Times editorial called on the FDA to remove from the label the unsupported suggestion that levonorgestrel emergency contraceptive pills inhibit implantation.^[123]

The primary mechanism of action of progesterone receptor modulator emergency contraceptive pills like low-dose (10 mg) and mid-dose (25 mg) mifepristone and ulipristal acetate (micronized 30 mg) is to prevent fertilization by inhibition or delay of ovulation.^[3]^[39]^[116]^[117]^[118]^[124] One clinical study found that post-ovulatory administration of ulipristal acetate altered the endometrium, but whether the changes would inhibit implantation is unknown.^[3]^[125] The European EMA-approved labels for ulipristal acetate emergency contraceptive pills do not mention an effect on implantation, but the U.S. FDA-approved label says: "alterations to the endometrium that may affect implantation may also contribute to efficacy."^[119]^[126]^[127]

The primary mechanism of action of copper-releasing intrauterine devices (IUDs) as emergency contraceptives is to prevent fertilization because of copper toxicity to sperm and ova.^[3]^[39] The very high effectiveness of copper-releasing IUDs as emergency contraceptives means they must also prevent some pregnancies by post-fertilization effects such as prevention of implantation.^[3]^[39]^[116]

United States legal and ethical controversies

A great deal of controversy accompanied the FDA approval of over-the-counter (OTC) access to Plan B. Supporters of over-the-counter access believe that easier access will reduce unintended pregnancy and abortion rates; some abortion opponents believe that EC itself is a form of abortion.^[128] The American Medical Association, the American Academy of Family Physicians, the American College of Obstetricians and Gynecologists, the American Academy of Pediatrics, and other leading U.S. medical organizations all supported OTC access.^[129] An advisory committee to the FDA recommended that Plan B be made available over the counter in 2003.^[130] In 2004, the FDA refused the advisory board's recommendation and prohibited over-the-counter sale, citing insufficient evidence that ECPs could be used safely by adolescents without medical supervision. In 2005, Susan F. Wood, assistant FDA commissioner for women's health and director of the Office of Women's Health, resigned to protest the FDA's delay.^[131] Reproductive rights supporters accused the FDA of basing the decision on political pressure from the pro-life lobby. The Center for Reproductive Rights filed a lawsuit regarding the approval process, which had not been resolved as of December 2006^[update]. In the legal proceedings, two senior FDA officials alleged in depositions that the decision to reject the OTC application was made on political, rather than scientific, grounds to "appease the administration's constituents".^[132]^[133] In 2006, the FDA approved over-the-counter access to Plan B for women 18 years of age and older.^[134] In April 2009, the FDA followed the ruling of a New York Federal District Court and loosened the restrictions to allow Duramed Pharmaceuticals to provide Plan B without a prescription to 17-year-olds. However, as of June 2009, Duramed had not yet put a non-prescription Plan B product for 17-year-olds through FDA approval, a process that could take some time.^[135]

A Massachusetts law that went into effect on 14 December 2005 requires all hospitals in the state to provide emergency contraception to any "female rape victim of childbearing age"^[136] including Catholic Hospitals who oppose the provision of emergency contraception. In a letter criticizing the joint UN/WHO Inter-agency Field Manual on Reproductive Health in Refugee Situations, the Catholic Church explains its belief that emergency contraception, along with IUDs and hormonal contraception, cannot be considered "solely contraceptive because in the case of effective fertilization a chemical abortion would be carried out during the first days of pregnancy."^[137] The Catholic position on family planning is explained further in Ethical and Religious Directives for Catholic Health Care Services.^[138] Because of this expressed moral stance against emergency contraception, the Massachusetts Catholic Conference opposed this law, stating interference with religious freedom. According to The New England Journal of Medicine, "compelling arguments can be made both for and against a pharmacist's right to refuse prescriptions for emergency contraception."^[139]

In isolated instances across the United States, pharmacists have refused to dispense emergency contraception even when presented with a legal prescription.^[140] In 2010, the Washington State Pharmacy Board decided that pharmacists do have a right to refuse to dispense emergency contraception.^[141] In addition, Wal-Mart, the nation's fifth-largest distributor of pharmaceuticals, refused to stock EC, beginning with Preven in 1999.^[142] However, Wal-Mart reversed this position when it was announced that stores would sell Plan B in March 2006.^[143]

The Congregation for the Doctrine of the Faith in the 2008 Instruction Dignitas Personae (Paragraph 23) stated that: "Alongside methods of preventing pregnancy which are, properly speaking, contraceptive, that is, which prevent conception following from a sexual act, there are other technical means which act after fertilization, when the embryo is already constituted, either before or after implantation in the uterine wall. Such methods are interceptive if they interfere with the embryo before implantation and contragestative if they cause the elimination of the embryo once implanted...Therefore, the use of means of interception and contragestation fall within the sin of abortion and are gravely immoral. Furthermore, when there is certainty that an abortion has resulted, there are serious penalties in canon law." ^[144]

References

^ Leung, Vivian W.Y.; Levine, Marc; Soon, Judith A. (2010). "Mechanisms of action of hormonal emergency contraceptives". Pharmacotherapy. 30 (2): 158–168. doi:10.1592/phco.30.2.158. PMID 20099990. {{cite journal}}: |access-date= requires |url= (help); Unknown parameter |month= ignored (help)
^ Gemzell-Danielsson, Kristina (2010). "Mechanism of action of emergency contraception". Contraception. 82 (5): 404–409. doi:10.1016/j.contraception.2010.05.004. PMID 20933113. {{cite journal}}: |access-date= requires |url= (help); Unknown parameter |month= ignored (help)
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Trussell, James; Schwarz, Eleanor Bimla (2011). "Emergency contraception". In Hatcher, Robert A.; Trussell, James; Nelson, Anita L.; Cates, Willard Jr.; Kowal, Deborah; Policar, Michael S. (eds.). Contraceptive technology (20th revised ed.). New York: Ardent Media. pp. 113–145. ISBN 978-1-59708-004-0. ISSN 0091-9721. OCLC 781956734. p. 121:
Mechanism of action
Copper-releasing IUCs
When used as a regular or emergency method of contraception, copper-releasing IUCs act primarily to prevent fertilization. Emergency insertion of a copper IUC is significantly more effective than the use of ECPs, reducing the risk of pregnancy following unprotected intercourse by more than 99%.^2,3 This very high level of effectiveness implies that emergency insertion of a copper IUC must prevent some pregnancies after fertilization.
Emergency contraceptive pills
To make an informed choice, women must know that ECPs—like the birth control pill, patch, ring, shot, and implant,⁷⁶ and even like breastfeeding⁷⁷—prevent pregnancy primarily by delaying or inhibiting ovulation and inhibiting fertilization, but may at times inhibit implantation of a fertilized egg in the endometrium. However, women should also be informed that the best available evidence indicates that ECPs prevent pregnancy by mechanisms that do not involve interference with post-fertilization events.
ECPs do not cause abortion⁷⁸ or harm an established pregnancy. Pregnancy begins with implantation according to medical authorities such as the US FDA, the National Institutes of Health⁷⁹ and the American College of Obstetricians and Gynecologists (ACOG).⁸⁰
Ulipristal acetate (UPA). One study has demonstrated that UP can delay ovulation.⁸¹... Another study found that UPA altered the endometrium, but whether this change would inhibit implantation is unknown.⁸²
p. 122:
Progestin-only emergency contraceptive pills. Early treatment with ECPs containing only the progestin levonorgestrel has been show to impair the ovulatory process and luteal function.^83–87
p. 123:
Combined emergency contraceptive pills. Several clinical studies have shown that combined ECPs containing ethinyl estradiol and levonorgestrel can inhibit or delay ovulation.^107–110
^ ^a ^b FDA (1997-02-25). "Certain combined oral contraceptives for use as postcoital emergency contraception". Fed Regist. 62 (37): 8610–2.
^ Trussell, James; Wynn, Lisa (2007-06-28). "Emergency Contraceptive Pills Worldwide". Princeton University. Retrieved 2007-06-30.{{cite web}}: CS1 maint: multiple names: authors list (link)
^ ^a ^b Stockton, Rachel. "ella:" Contraceptive Method or Abortion Agent? Food Consumer. June 12, 2010.
^ ^a ^b ^c ^d WHO Task Force on Postovulatory Methods of Fertility Regulation (August 8, 1998). "Randomised controlled trial of levonorgestrel versus the Yuzpe regimen of combined oral contraceptives for emergency contraception". Lancet. 352 (9126): 428–433. doi:10.1016/S0140-6736(98)05145-9. PMID 9708750.
^ ^a ^b ^c OPR & ARHP (2007-06-18). "Emergency contraception: Pill brands, doses, and instructions". Princeton University. Retrieved 2007-06-30.
^ OPR & ARHP (2007-06-18). "Ovral". Princeton University. Retrieved 2007-06-30.
^ Weiss, Deborah; Friedman, Deborah (2006-12-13). "Emergency contraception". PPFA. Retrieved 2007-06-30.{{cite web}}: CS1 maint: multiple names: authors list (link) ^{[dead link]}
^ ^a ^b Gemzell-Danielsson, Kristina (2011). "Ulipristal acetate (ellaOne®) for emergency contraception: review of the clinical evidence". Future Science. 1 (3): 467–472. doi:10.4155/cli.11.6. Retrieved 16 March 2011. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
^ Watson PR (1 December 2010). "Watson Launches ella(R)(ulipristal acetate)". Retrieved 12-1-2010. {{cite web}}: Check date values in: |accessdate= (help)
^ "Planned Parenthood - Mifepristone: Expanding Women's Options for Early Abortion". Retrieved July 23, 2006.
^ Piaggio G; et al. (2003). "Meta-analysis of randomized trials comparing different doses of mifepristone in emergency contraception". Contraception. 68 (6): 447–52. doi:10.1016/S0010-7824(03)00142-2. PMID 14698075. {{cite journal}}: Unknown parameter |author-separator= ignored (help)
^ Wertheimer, Randy E. (2000-11-15). "Emergency Postcoital Contraception". American Family Physician. American Academy of Family Physicians. Retrieved 2006-07-23.
^ Ho; Pak Chung; et al. (2002). "Mifepristone: Contraceptive and Non-Contraceptive Uses". Current Opinions in Obstetrics Gynecology. 14 (3): 325–230. doi:10.1097/00001703-200206000-00013. PMID 12032390. {{cite journal}}: Unknown parameter |author-separator= ignored (help)
^ Gemzell-Danielsson, K. (2004-06-10). "Mechanisms of action of mifepristone and levonorgestrel when used for emergency contraception". Human Reproduction Update. 10 (4). Oxford University Press: 341–348. doi:10.1093/humupd/dmh027. PMID 15192056. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
^ Weismiller D (2004). "Emergency contraception". Am Fam Physician. 70 (4): 707–14. PMID 15338783. Retrieved 2006-12-01.
^ "Plan B label information" (PDF). Food and Drug Administration. 2006. Archived from the original (PDF) on 2007-01-24. Retrieved 2007-07-03. {{cite web}}: Unknown parameter |month= ignored (help)
^ Trussell J, Rodriguez G, Ellertson C (1999). "Updated estimates of the effectiveness of the Yuzpe regimen of emergency contraception". Contraception. 59 (3): 147–51. doi:10.1016/S0010-7824(99)00018-9. PMID 10382076.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Trussell J, Ellertson C, von Hertzen H, Bigrigg A, Webb A, Evans M, Ferden S, Leadbetter C (2003). "Estimating the effectiveness of emergency contraceptive pills". Contraception. 67 (4): 259–65. doi:10.1016/S0010-7824(02)00535-8. PMID 12684144.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ <Please add first missing authors to populate metadata.> (1999). "Counsel women to take ECPs as soon as possible". Contracept Technol Update. 20 (7): 75–7. PMID 12295381.
^ WHO/HRP (1999). "Levonorgestrel is more effective, has fewer side-effects, than Yuzpe regimen". Prog Hum Reprod Res (51): 3–5. PMID 12349416.
^ ^a ^b ^c von Hertzen, Helena; Piaggio, Gilda; Peregoudov, Alexandre; Ding, Juhong; Chen, Junling; Song, Si; Bártfai, György; Ng, Ernest; Gemzell-Danielsson, Kristina; Oyunbileg, Amindavaa; Wu, Shangchun; Cheng, Weiyu; Lüdicke, Frank; Pretnar-Darovec, Alenka; Kirkman, Rosemary; Mittal, Suneeta; Khomassuridze, Archil; Apter, Dan; WHO Research Group on Post-ovulatory Methods of Fertility Regulation (December 7, 2002). "Low dose mifepristone and two regimens of levonorgestrel for emergency contraception: a WHO multicentre randomised trial". Lancet. 360 (9348): 1803–1810. doi:10.1016/S0140-6736(02)11767-3. PMID 12480356.
^ Piaggio G, Heng Z, von Hertzen H, Bilian X, Linan C (2003). "Combined estimates of effectiveness of mifepristone 10 mg in emergency contraception". Contraception. 68 (6): 439–46. doi:10.1016/S0010-7824(03)00110-0. PMID 14698074.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Cheng L, Gulmezoglu AM, Oel CJ, Piaggio G, Ezcurra E, Look PF (2004). Cheng, Linan (ed.). "Interventions for emergency contraception". Cochrane Database Syst Rev (3): CD001324. doi:10.1002/14651858.CD001324.pub2. PMID 15266446.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Dixon GW, Schlesselman JJ, Ory HW, Blye RP (1980). "Ethinyl estradiol and conjugated estrogens as postcoital contraceptives". JAMA. 244 (12): 1336–9. doi:10.1001/jama.244.12.1336. PMID 6251288.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Trussell J, Ellertson C, Stewart F (1996). "The effectiveness of the Yuzpe regimen of emergency contraception". Fam Plann Perspect. 28 (2): 58–64, 87. doi:10.2307/2136125. JSTOR 2136125. PMID 8777940.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ ^a ^b ^c ^d ^e ^f ^g Trussell, James; Raymond (April 2012). "Emergency contraception: a last chance to prevent unintended pregnancy" (PDF). Princeton: Office of Population Research at Princeton University, Association of Reproductive Health Professionals. Retrieved 2012-04-30. {{cite web}}: Unknown parameter |lfirst2= ignored (help)
^ Espinos JJ, Rodriguez-Espinosa J, Senosiain R, Aura M, Vanrell C, Gispert M, Vega C, Calaf J (1999). "The role of matching menstrual data with hormonal measurements in evaluating effectiveness of postcoital contraception". Contraception. 60 (4): 243–7. doi:10.1016/S0010-7824(99)00090-6. PMID 10640171.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ ^a ^b ^c ^d ^e American Academy of Pediatrics Committee on Adolescence (October 2005). "Emergency contraception". Pediatrics. 116 (4): 1026–1035. doi:10.1542/peds.2005-1877. PMID 16147972.
^ ^a ^b ^c ^d Grimes, David A.; Raymond, Elizabeth G. (August 6, 2002). "Emergency contraception". Ann Intern Med. 137 (3): 180–189. PMID 12160366.
^ ^a ^b ^c ^d American College of Obstetricians and Gynecologists (May 2010). "ACOG Practice Bulletin No. 112: Emergency contraception". Obstet Gynecol. 115 (5): 1100–1109. doi:10.1097/AOG.0b013e3181deff2a. PMID 20410799.
^ ^a ^b ^c FDA Center for Drug Evaluation and Research (August 22, 2006). "Plan B Rx to OTC switch Medical Reviews" (PDF). Beltsville, Md.: Food and Drug Administration. pp. 32–7, 133–77. Retrieved 2006-12-13.
^ ^a ^b ^c ^d WHO Department of Reproductive Health and Research (2009). "Emergency contraceptive pills (ECPs)". Medical eligibility criteria for contraceptive use (PDF) (4th ed.). Geneva: World Health Organization. p. 63. ISBN 978-92-4-156388-8.
^ ^a ^b ^c ^d RCOG Faculty of Sexual & Reproductive Healthcare (2009). "UK medical eligibility criteria for contraceptive use" (PDF). London: Royal College of Obstetricians and Gynaecologists. pp. 107–115. Retrieved 2012-04-30. {{cite web}}: |chapter= ignored (help)
^ CDC Division of Reproductive Health (June 18, 2010). "U.S. Medical eligibility criteria for contraceptive use, 2010" (PDF). MMWR Recomm Rep. 59 (RR-4): 1–86. PMID 20559203.
^ ^a ^b Davidoff, Frank; Trussell, James (October 11, 2006). "Plan B and the politics of doubt (commentary)". JAMA. 296 (14): 1775–1778. doi:10.1001/jama.296.14.1775. PMID 17032991.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k RCOG Faculty of Sexual & Reproductive Healthcare, Clinical Effectiveness Unit (January 2012). Clinical guidance: emergency contraception (PDF). London: Royal College of Obstetricians and Gynaecologists. ISSN 1755-103X. Retrieved 2012-04-30. p.3:
How does EC work?
In 2002, a judicial review ruled that pregnancy begins at implantation, not fertilisation.⁸ The possible mechanisms of action should be explained to the patient as some methods may not be acceptable, depending on individual beliefs about the onset of pregnancy and abortion.
Copper-bearing intrauterine device (Cu-IUD). Copper is toxic to the ovum and sperm and thus the copper-bearing intrauterine device (Cu-IUD) is effective immediately after insertion and works primarily by inhibiting fertilisation.^9–11 A systematic review on mechanisms of action of IUDs showed that both pre- and postfertilisation effects contribute to efficacy.¹¹ If fertilisation has already occurred, it is accepted that there is an anti-implantation effect,^12,13
Levonorgestrel (LNG). The precise mode of action of levonorgestrel (LNG) is incompletely understood but it is thought to work primarily by inhibition of ovulation.^16,17
Ulipristal acetate (UPA). UPA’s primary mechanism of action is thought to be inhibition or delay of ovulation.²
^ RCOG Faculty of Sexual & Reproductive Healthcare, Clinical Effectiveness Unit (January 2012). Clinical guidance: drug interactions with hormonal contraception (PDF). London: Royal College of Obstetricians and Gynaecologists. ISSN 1755-103X. Retrieved 2012-04-30.
^ Trussell, James; Hedley, Allison; Raymond, Elizabeth (October 2003). "Ectopic pregnancy following use of progestin-only ECPs (letter)" (PDF). J Fam Plann Reprod Health Care. 29 (4): 249. doi:10.1783/147118903101197944. PMID 14662065.
^ ^a ^b ^c UNDP/UNFPA/WHO/World Bank Special Programme of Research, Development and Research Training in Human Reproduction (HRP) (March 25, 2010). "Fact sheet on the safety of levonorgestrel-alone emergency contraceptive pills (LNG ECPs)" (PDF). Geneva: World Health Organization.
Can LNG ECPs cause an abortion?
LNG ECPs do not interrupt an established pregnancy or harm a developing embryo.¹⁵ The evidence available to date shows that LNG ECP use does not prevent a fertilized egg from attaching to the uterine lining. The primary mechanism of action is to stop or disrupt ovulation; LNG ECP use may also prevent the sperm and egg from meeting.¹⁶
^ Cleland, Kelly; Raymond, Elizabeth; Trussell, James; Cheng, Linan; Zhu, Haoping (June 2010). "Ectopic pregnancy and emergency contraceptive pills: a systematic review". Obstet Gynecol. 115 (6): 1263–1266. doi:10.1097/AOG.0b013e3181dd22ef. PMID 20502299.
^ WHO Department of Reproductive Health and Research (December 31, 2004). "Question 20. What can a woman do to prevent nausea and vomiting when taking emergency contraceptive pills (ECPs)?". Selected practice recommendations for contraceptive use (2nd ed.). Geneva: World Health Organization. ISBN 92-4-156284-6. {{cite book}}: External link in |chapterurl= (help); Unknown parameter |chapterurl= ignored (|chapter-url= suggested) (help)
^ WHO Department of Reproductive Health and Research (December 31, 2004). "Question 21. What can a woman do if she vomits after taking emergency contraceptive pills (ECPs)?". Selected practice recommendations for contraceptive use (2nd ed.). Geneva: World Health Organization. ISBN 92-4-156284-6. {{cite book}}: External link in |chapterurl= (help); Unknown parameter |chapterurl= ignored (|chapter-url= suggested) (help)
^ ^a ^b Raymond, Elizabeth G.; Goldberg, Alisa; Trussell, James; Hays, Melissa; Roach, Elizabeth; Taylor, Douglas (April 2006). "Bleeding patterns after use of levonorgestrel emergency contraceptive pills". Contraception. 73 (4): 376–381. doi:10.1016/j.contraception.2005.10.006. PMID 16531171.
^ Gainer, Erin; Kenfack, Bruno; Mboudou, Emile; Doh, Anderson Sama; Bouyer, Jean (August 2006). "Menstrual bleeding patterns following levonorgestrel emergency contraception". Contraception. 74 (2): 118–124. doi:10.1016/j.contraception.2006.02.009. PMC 1934349. PMID 16860049.
^ Gemzell-Danielsson, Kristina; Marions, Lena (July–August 2004). "Mechanisms of action of mifepristone and levonorgestrel when used for emergency contraception". Hum Reprod Update. 10 (4): 341–348. doi:10.1093/humupd/dmh027. PMID 15192056.
^ Gottardi G, Spreafico A, de Orchi L (1986). "The postcoital IUD as an effective continuing contraceptive method". Contraception. 34 (6): 549–58. doi:10.1016/S0010-7824(86)80011-7. PMID 3549140.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ ^a ^b Ellertson, Charlotte (March/April 1996). "History and Efficacy of Emergency Contraception: Beyond Coca-Cola". Family Planning Perspectives. 28 (2). Guttmacher Institute. Retrieved 2006-11-22. {{cite journal}}: Check date values in: |date= (help)
^ Chernev T, Ivanov S, Dikov I, Stamenkova R (1995). "Prospective study of contraception with levonorgestrel". Plan Parent Eur. 24 (2): 25. PMID 12290800.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ ^a ^b "Effectiveness of Emergency Contraceptives". The Emergency Contraception Website. Office of Population Research at Princeton University and the Association of Reproductive Health Professionals. 2006. Retrieved 2006-12-02. {{cite web}}: Unknown parameter |month= ignored (help)
^ Bakhtiar, Saadia (2000). "Contraception". Pakistan Journal of Family Medicine. 11: 19–24. Retrieved 2006-12-02. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
^ "What is Emergency Contraception?". The Emergency Contraception Website. Office of Population Research at Princeton University and the Association of Reproductive Health Professionals. 2006. Retrieved 2006-12-02. {{cite web}}: Unknown parameter |month= ignored (help)
^ "Birth Control: The Morning-After Pill". Time. 1966-05-06. Retrieved 2010-05-01.
^ <Please add first missing authors to populate metadata.> (1967). "Postcoital contraception". IPPF Med Bull. 1 (4): 3. PMID 12254703.
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^ <Please add first missing authors to populate metadata.> (1973). "FDA considers DES safe as 'morning-after' pill". JAMA. 224 (12): 1581–2. PMID 12257949.
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^ Yuzpe A, Thurlow H, Ramzy I, Leyshon J (1974). "Post coital contraception—A pilot study". J Reprod Med. 13 (2): 53–8. PMID 4844513.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Valle G (1975). "The problem of postcoital contraception using oral progestins". Aggiorn Ostet Ginecol. 8 (3): 127–8. PMID 12334868.
^ <Please add first missing authors to populate metadata.> (1975). "Copper IUD, inserted after coitus averts pregnancy and provides continuing contraceptive protection". Int Fam Plann Dig. 1 (3): 11–2. doi:10.2307/2948217. JSTOR 2948217. PMID 12307393.
^ "Danazol". Medscape. 2002. Retrieved 2006-11-08.
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^ FDA (1997). "Certain combined oral contraceptives for use as postcoital emergency contraception". Fed Regist. 62 (37): 8610. {{cite journal}}: Unknown parameter |month= ignored (help) "Since the United Kingdom approved emergency contraceptive pills in 1984, more than 4 million prescriptions have been recorded. However, the actual use is much greater because providers have found it less expensive to provide tablets of identical drugs taken from products packaged as combined oral contraceptives."
^ "Sponsors". Fertility. 2002. Retrieved 2006-12-01.
^ Task Force on Postovulatory Methods of Fertility Regulation (1998). "Randomised controlled trial of levonorgestrel versus the Yuzpe regimen of combined oral contraception for emergency contraception". Lancet. 352 (9126): 428–433. doi:10.1016/S0140-6736(98)05145-9. PMID 9708750.
^ Guillebaud J (1998). "Time for emergency contraception with levonorgestrel alone". Lancet. 352 (9126): 416–417. doi:10.1016/S0140-6736(98)22032-0. PMID 9708743.
^ "Morning after pill courier service launched". Telegraph. 2012. Retrieved 2012-04-17.
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^ Demers LM (1971). "The morning-after pill". N Engl J Med. 284 (18): 1034–6. doi:10.1056/NEJM197105062841813. PMID 5553470.
^ Kuchera LK (1971). "Postcoital contraception with diethylstilbestrol". JAMA. 218 (4): 562–3. doi:10.1001/jama.218.4.562. PMID 5171004.
^ FDA (1973). "Postcoital diethylstilbestrol". FDA Drug Bull. 119 (2): 87–8. PMC 1455105. PMID 18730987. {{cite journal}}: Unknown parameter |month= ignored (help)
^ ^a ^b ^c U.S. Senate (1975). Regulation of diethylstilbestrol (DES), 1975: Joint Hearing before the Subcommittee on Health and the Subcommittee on Administrative Practice and Procedure, 94th Congress, 1st Session on S. 963, February 27, 1975. Washington: U.S. Govt. Print. Off.
^ FDA (1973). "Diethylstilbestrol. Use as postcoital contraceptive; patient labeling". Fed Regist. 38 (186): 26809–11. {{cite journal}}: Unknown parameter |month= ignored (help)
^ ^a ^b ^c FDA (1975). "Estrogens for oral or parenteral use. Drugs for human use; drug efficacy study; amended notice". Fed Regist. 40 (39): 8242. {{cite journal}}: Unknown parameter |month= ignored (help)
^ FDA (1973). "Certain estrogens for oral use. Notice of withdrawal of approval of new drug applications". Fed Regist. 38 (186): 26824–6. {{cite journal}}: Unknown parameter |month= ignored (help)
^ ^a ^b Dutton, Diana B. (1988). Worse than the disease: pitfalls of medical progress. Cambridge: Cambridge University Press. ISBN 0-521-34023-3.
^ FDA (1975). "Diethylstilbestrol as postcoital oral contraceptive; patient labeling". Fed Regist. 40 (25): 5351–5. {{cite journal}}: Unknown parameter |month= ignored (help)
^ FDA (1975). "Certain estrogens for oral use or parenteral use. Drugs for human use; drug efficacy study implementation; follow-up notice". Fed Regist. 40 (25): 5384. {{cite journal}}: Unknown parameter |month= ignored (help)
^ FDA (1978). "DES and Breast Cancer". FDA Drug Bull. 8 (2): 10. {{cite journal}}: Unknown parameter |month= ignored (help)
^ Hatcher, Robert A.; Stewart, Gary K., Stewart, Felicia; Guest, Felicia; Schwartz, David W.; Jones, Stephanie A. (1980). Contraceptive Technology 1980–1981 (10th ed.). New York: Irvington Publishers. pp. 128–33. ISBN 0-8290-0084-4.{{cite book}}: CS1 maint: multiple names: authors list (link)
^ Hatcher, Robert A.; Stewart, Gary K., Stewart, Felicia; Guest, Felicia; Josephs, Nancy; Dale, Janet (1982). Contraceptive Technology 1982–1983 (11th ed.). New York: Irvington Publishers. pp. 152–7. ISBN 0-8290-0705-9.{{cite book}}: CS1 maint: multiple names: authors list (link)
^ Ibarreta, Dolores; Swain, Shanna H. (2001). "The DES story: long-term consequences of prenatal use". In in Harremoës, Poul; Gee, David; Vaz, Sofia Guedes (eds.) (ed.). Late lessons from early warnings: the precautionary principle 1896–2000 (PDF). Copenhagen: European Environmental Agency. pp. 84–92. ISBN 92-9167-323-4. Retrieved 2006-12-07. {{cite book}}: |editor= has generic name (help)CS1 maint: multiple names: authors list (link)
^ FDA (1997). "Certain combined oral contraceptives for use as postcoital emergency contraception". Fed Regist. 62 (37): 8610–2. {{cite journal}}: Unknown parameter |month= ignored (help)
^ FDA (1998). "Preven approval package" (PDF). Archived from the original (PDF) on 2006-10-11. Retrieved 2006-12-10. {{cite web}}: Unknown parameter |month= ignored (help)
^ California Board of Pharmacy (2004). "Pharmacists protocol for dispensing emergency contraception" (PDF). Retrieved 2006-12-10. {{cite web}}: Unknown parameter |month= ignored (help)
^ FDA (1999). "Plan B approval package". Archived from the original on 2006-10-11. Retrieved 2006-12-10. {{cite web}}: Unknown parameter |month= ignored (help)
^ FDA (2006). "Plan B information page". Retrieved 2006-12-10. {{cite web}}: Unknown parameter |month= ignored (help)
^ Barr Pharmaceuticals (2006). "Barr Launches Plan B OTC/Rx Dual-Label Product; Awarded 3 Years New Product Exclusivity". Retrieved 2006-12-12. {{cite web}}: Unknown parameter |month= ignored (help)
^ Harris, Gardiner (April 22, 2009). "F.D.A. Easing Access to 'Morning After' Pill". The New York Times.
^ ^a ^b International Consortium for Emergency Contraception (ICEC) webpage, section on "History". Accessed 30 November 2006.
^ ^a ^b ICEC web page, section on "Products and Availability". Accessed 30 November 2006.
^ "Concept Foundation". Initiative on Public-Private Partnerships for Health. 2006-03-07. Archived from the original on 2006-10-10. Retrieved 2006-11-17. Funding data requires free registration to view.
^ "IPPF Launches New EC Pill at ICEC Meeting". Consortium News. 2006. Retrieved 2006-11-17. {{cite web}}: Unknown parameter |month= ignored (help)
^ Glasier A, Baird D (1998). "The effects of self-administering emergency contraception". N Engl J Med. 339 (1): 1–4. doi:10.1056/NEJM199807023390101. PMID 9647872.
^ Raine T, Harper C, Leon K, Darney P (2000). "Emergency contraception: advance provision in a young, high-risk clinic population". Obstet Gynecol. 96 (1): 1–7. doi:10.1016/S0029-7844(00)00830-9. PMID 10862832.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Jackson RA, Schwarz EB, Freedman L, Darney P (2003). "Advance supply of emergency contraception: effect on use and usual contraception―a randomized trial". Obstet Gynecol. 102 (1): 8–16. doi:10.1016/S0029-7844(03)00478-2. PMID 12850599.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Gold MA, Wolford JE, Smith KA, Parker AM (2004). "The effects of advance provision of emergency contraception on adolescent women's sexual and contraceptive behaviors". J Pediatr Adolesc Gynecol. 17 (2): 87–96. doi:10.1016/j.jpag.2003.11.018. PMID 15050984.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Lo SS, Fan SYS, Ho PC, Glasier AF (2004). "Effect of advanced provision of emergency contraception on women's contraceptive behavior: a randomized controlled trial". Hum Reprod. 19 (10): 2404–10. doi:10.1093/humrep/deh425. PMID 15333602.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Raine TR, Harper CC, Rocca CH, Fischer R, Padian N, Klausner JD, Darney PD (2005). "Direct access to emergency contraception through pharmacies and effect on unintended pregnancy and STIs: a randomized controlled trial". JAMA. 293 (1): 54–62. doi:10.1001/jama.293.1.54. PMID 15632336.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Hu X, Cheng L, Hua X, Glasier A (2005). "Advanced provision of emergency contraception to postnatal women in China makes no difference in abortion rates: a randomized controlled trial". Contraception. 72 (2): 111–6. doi:10.1016/j.contraception.2005.02.004. PMID 16022849.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Belzer M, Sanchez K, Olson J, Jacobs AM, Tucker D (2005). "Advance supply of emergency contraception: a randomized trial in adolescent mothers". J Pediatr Adolesc Gynecol. 18 (5): 347–54. doi:10.1016/j.jpag.2005.06.007. PMID 16202939.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Trussell J, Raymond E, Stewart FH (2006). "Advance supply of emergency contraception: a randomized trial in adolescent mothers (Letter to the editor)". J Pediatr Adolesc Gynecol. 19 (3): 251. doi:10.1016/j.jpag.2006.02.016. PMID 16731424.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Walsh TL, Frezieres RG (2006). "Patterns of emergency contraception use by age and ethnicity from a randomized trial comparing advance provision and information only". Contraception. 74 (2): 110–7. doi:10.1016/j.contraception.2006.02.005. PMID 16860048.
^ Raymond EG, Stewart F, Weaver M, Monteith C, Van Der Pol B (2006). "Impact of increased access to emergency contraceptive pills: a randomized controlled trial". Obstet Gynecol. 108 (5): 1098–106. doi:10.1097/01.AOG.0000235708.91572.db. PMID 17077230.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Kosunen E, Sihvo S, Hemminki E (1997). "Knowledge and use of hormonal emergency contraception in Finland". Contraception. 55 (3): 153–7. doi:10.1016/S0010-7824(97)00022-X. PMID 9115003.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ "Emergency Contraception Doesn't Lower Abortion Rates". Forbes. September 15, 2006. Archived from the original on 2006-10-09. Retrieved 2006-09-23.
^ Glasier A, Fairhurst K, Wyke S, Zieblad S, Seaman P, Walker J, Lakha F (2004). "Advanced provision of emergency contraception does not reduce abortion rates". Contraception. 69 (5): 36. doi:10.1016/j.contraception.2004.01.002. PMID 15105057. {{cite journal}}: More than one of |pages= and |page= specified (help)CS1 maint: multiple names: authors list (link)
^ Hu X; et al. (2005). "Advanced provision of emergency contraception to postnatal women in China makes no difference in abortion rates: a randomized controlled trial". Contraception. 72 (2): 111–6. doi:10.1016/j.contraception.2005.02.004. PMID 16022849. {{cite journal}}: Unknown parameter |author-separator= ignored (help)
^ Glasier, A (2006). "Emergency contraception: Is it worth all the fuss?". BMJ. 333 (7568): 560–1. doi:10.1136/bmj.38960.672998.80. PMID 16973989.
^ Glover D eta al (1976). "Diethylstilbestrol in the Treatment of Rape Victims". The Western journal of medicine. 125 (4). West J Med: 331–4. PMC 1237330. PMID 1032235.
^ Diamond EF (1978). "Physician notes hazards of DES use to prevent pregnancy". Hosp Prog. 59 (3): 6–10. PMID 631811.
^ Holmes MM; et al. (1996). "Rape-related pregnancy: estimates and descriptive characteristics from a national sample of women". Am J Obstet Gynecol. 175 (2): 320–4. doi:10.1016/S0002-9378(96)70141-2. PMID 8765248 Template:Inconsistent citations {{cite journal}}: Unknown parameter |author-separator= ignored (help)CS1 maint: postscript (link)
^ Stewart, Felicia H. (2000). "Prevention of pregnancy resulting from rape: A neglected preventive health measure". American Journal of Preventive Medicine. 19 (4): 228–229. doi:10.1016/S0749-3797(00)00243-9. PMID 11064225. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
^ ^a ^b ^c ^d Speroff, Leon; Darney, Philip D. (2011). "Special uses of oral contraception: emergency contraception, the progestin-only minipill". A clinical guide for contraception (5th ed.). Philadelphia: Lippincott Williams & Wilkins. pp. 153–166. ISBN 978-1-60831-610-6. p. 155:
Emergency postcoital contraception
Levonorgestrel
Mechanism and efficacy
There is strong evidence that treatment with emergency contraception acts primarily by preventing or delaying ovulation and by preventing fertilization.^22–26 Studies have indicated that emergency contraception does not prevent implantation.^27–29 Experiments in monkeys and rats could detect no effect of a high dose of levonorgesterel administered postcoitally once fertilization had occurred.^30,31 The evidence indicates that a postfertilization effect does not contribute to the efficacy of emergency contraception.^25,30–33 Clinicians, pharmacists, and patients can be reassured that treatment with emergency contraception is not an abortifacient.
p. 157:
The use of progesterone receptor modulators for emergency contraception
Mifepristone. In randomized trials, 10 mg mifepristone was as effective as 25, 50, or 600 mg. preventing about 80-85% of expected pregnancies (the same efficacy and side effects as with the levonorgestrel method), with a slight decrease in efficacy when treatment was delayed to 5 days after intercourse.^16,52–54
Ulipristal Acetate. Ulipristal acetate (ellaOne) has similar biologic effects as mifepristone and is approved for emergency contraception in Europe and is expected to become available in the U.S.in a single oral dose of 30 mg. Randomized trials demonstrated that ulipristal acetate is slightly more effective than the single 1.5 mg dose of levonorgestrel when used within 72 h after sexual intercourse and even between 72 h and 120h.^55,56 … Progesterone receptor modulators like ulipristal acetate and mifepristone suppress ovarian follicular growth and also delay endometrial maturation, manifested in a delay in menstruation after treatment. Ovulation can be temporarily postponed.
Other methods
Another method of emergency contraception is the insertion of a copper IUD, anytime during the preovulatory phase of the menstrual cycle and up to 5 days after ovulation. The failure rate (in a small number of studies) is very low, 0.1%.^34,35 This method definitely prevents implantation, but it is not suitable for women who are not candidates for intrauterine contraception, e.g., multiple sexual partners or a rape victim. The use of a copper IUD for emergency contraception is expensive, but not if it is retained as an ongoing method of contraception.
^ ^a ^b ^c Jensen, Jeffrey T.; Mishell, Daniel R. Jr. (2012). "Family planning: contraception, sterilization, and pregnancy termination". In Lentz, Gretchen M.; Lobo, Rogerio A.; Gershenson, David M.; Katz, Vern L. (eds.). Comprehensive gynecology. Philadelphia: Mosby Elsevier. pp. 215–272. ISBN 978-0-323-06986-1. {{cite book}}: More than one of |editor= and |editor1-last= specified (help) p. 257:
Emergency contraception
It is believed that the main mechanism of action of high-dose progestin emergency contraception is inhibition of ovulation, but other mechanisms may be involved... Taken together, these data are highly supportive of the concept that levonorgestrel emergency contraception has little or no effect on postovulation events but is highly effective when taken before ovulation. Levonorgestrel emergency contraception does not affect implantation and is not abortifacient.
Intrauterine insertion of a copper IUD within 5 to 10 days of midcycle coitus is a very effective method of preventing continuation of the pregnancy… The LNG-IUS should not be used for emergency contraception.
A study by the WHO reported that use of a single tablet of 10 mg of mifepristone was an effective emergency contraceptive with a pregnancy rate of 1.2%.
Ulipristal, also known as CDB-2914, has been studied as an emergency contraceptive pill… In 2009, European regulatory approval was granted for a 30-mg tablet of ulipristal (under the brand name of EllaOne) as an emergency contraceptive pill for use up to 5 days after unprotected intercourse. An application for approval in the United States is under review.
^ ^a ^b ^c Flatow, Ira (June 15, 2012). "How the morning-after pill works (interview with Kristina Gemzell-Danielsson, MD, Professor and Chair, Division of Obstetrics and Gynecology, Karolinska Institute, Stockholm, Sweden)". Talk of the Nation Science Friday. New York: NPR.
^ ^a ^b ^c ^d Belluck, Pam (June 6, 2012). "No abortion role seen for morning-after pill". The New York Times. p. A1.
Belluck, Pam (June 6, 2012). "Drug's nickname may have aided politicization". The New York Times. p. A14.
^ Bayer (March 22, 2010). "Summary of Product Characteristics: Levonelle One Step 1500 mcg; 5.1 Pharmacodynamic properties". London: electronic Medicines Compendium (eMC), Datapharm. The precise mode of action of Levonelle One Step is not known. At the recommended regimen, levonorgestrel is thought to work mainly by preventing ovulation and fertilisation if intercourse has taken place in the preovulatory phase, when the likelihood of fertilisation is the highest. It may also cause endometrial changes that discourage implantation. Levonelle One Step is not effective once the process of implantation has begun.
HRA Pharma (July 19, 2011). "Summary of Product Characteristics: NorLevo 1.5 mg; 5.1 Pharmacodynamic properties". Dublin: Irish Pharmaceutical Healthcare Association. The precise mode of action of Norlevo 1.5 mg is not known. At the used regimen, levonorgestrel is believed to suppress ovulation thus preventing fertilization if the intercourse has taken place in the preovulatory phase when the likelihood of fertilization is the highest. It could also prevent implantation. It is not effective once the process of implantation has begun.
^ Duramed Pharmaceuticals/Barr Pharmaceuticals (now Teva Women's Health) (July 9, 2010). "Prescribing information: Plan B One-Step; 12.1 Mechanism of action" (PDF). Silver Spring, Md.: FDA Center for Drug Evaluation and Research (CDER). p. 4. Emergency contraceptive pills are not effective if a woman is already pregnant. Plan B One-Step is believed to act as an emergency contraceptive principally by preventing ovulation or fertilization (by altering tubal transport of sperm and/or ova). In addition, it may inhibit implantation (by altering the endometrium). It is not effective once the process of implantation has begun.
^ International Federation of Gynecology and Obstetrics (FIGO) and International Consortium for Emergency Contraception (ICEC) (April 4, 2011). "Mechanism of action: How do levonorgestrel-only emergency contraceptive pills (LNG ECPs) prevent pregnancy?" (PDF). London: International Federation of Gynecology and Obstetrics.
Levonorgestrel-only emergency contraceptive pills:
• Interfere with the process of ovulation;
• May possibly prevent the sperm and the egg from meeting.
Implications of the research:
• Inhibition or delay of ovulation is LNG ECPs principal and possibly only mechanism of action.
• Review of the evidence suggests that LNG ECPs cannot prevent implantation of a fertilized egg. Language on implantation should not be included in LNG ECP product labeling.
• The fact that LNG ECPs have no demonstrated effect on implantation explains why they are not 100% effective in preventing pregnancy, and are less effective the later they are taken. Women should be given a clear message that LNG ECPs are more effective the sooner they are taken.
• LNG ECPs do not interrupt a pregnancy (by any definition of the beginning of pregnancy). However, LNG ECPs can prevent abortions by reducing unwanted pregnancies.
^ editorial (June 9, 2012). "How morning-after pills really work". The New York Times. p. A20. The F.D.A. now acknowledges that the emerging data suggest the morning-after pill, often called Plan B, does not inhibit implantation. It should remove that unsupported suggestion from the label.
^ Cheng, Linan; Che, Yan; Gülmezoglu, A. Metin (August 15, 2012). "Interventions for emergency contraception". Cochrane Database of Systematic Reviews. 8: CD001324. doi:10.1002/14651858.CD001324.pub4. PMID 22895920.
^ Stratton, Pamela; Levens, Eric D.; Hartog, Beth; Piquion, Johann; Wei, Qingxiang; Merino, Maria; Nieman, Lynnette K. (April 2010). "Endometrial effects of a single early luteal dose of the selective progesterone receptor modulator CDB-2914". Fertility and Sterility. 93 (6): 2035–2041. doi:10.1016/j.fertnstert.2008.12.057. PMC 2911236. PMID 19200989. Post-ovulatory early luteal phase administration of 10–100 mg of ulipristal acetate resulted in a statistically significant dose-dependent 0.6 ± 2.2 mm decrease in endometrial thickness from a baseline of 10.3 ± 2.3 mm to 9.7 ± 1.8 mm (vs. a 1.3 ± 2.3 mm increase in endometrial thickness from a baseline of 10.2 ± 3.2 mm to 11.5 ± 4.1 mm with placebo administration) which the authors hypothesized could hamper implantation.
^ HRA Pharma (March 15, 2012). "Summary of Product Characteristics: ellaOne 30 mg; 5.1 Pharmacodynamic properties" (PDF). London: European Medicines Agency. p. 7. Ulipristal acetate is an orally-active synthetic selective progesterone receptor modulator which acts via high-affinity binding to the human progesterone receptor. The primary mechanism of action is inhibition or delay of ovulation. Pharmacodynamic data show that even when taken immediately before ovulation is scheduled to occur, ulipristal acetate is able to postpone follicular rupture in some women.
^ Watson Pharma (under license from HRA Pharma) (May 2, 2012). "Prescribing information: Ella; 12.1 Mechanism of action" (PDF). Silver Spring, Md.: FDA Center for Drug Evaluation and Research (CDER). pp. 4–5. When taken immediately before ovulation is to occur, ella postpones follicular rupture. The likely primary mechanism of action of ulipristal acetate for emergency contraception is therefore inhibition or delay of ovulation; however, alterations to the endometrium that may affect implantation may also contribute to efficacy... The pharmacodynamics of ulipristal acetate depends on the timing of administration in the menstrual cycle. Administration in the mid-follicular phase causes inhibition of folliculogenesis and reduction of estradiol concentration. Administration at the time of the luteinizing hormone peak delays follicular rupture by 5 to 9 days. Dosing in the early luteal phase does not significantly delay endometrial maturation but decreases endometrial thickness by 0.6 ± 2.2 mm (mean ± SD).
^ "Q&A: The Debate over the Morning-After Pill". NPR. 2006-08-15. Retrieved 2006-11-11.
^ "Briefing Document (1.2.4 Plan B: Rx-to-OTC Switch)". FDA.gov: December 16, 2003. Accessed August 2, 2006.
^ "Panel backs over-the-counter 'morning-after' pill". CNN.com. 2003-12-17. Retrieved April 28, 2006.
^ FDA Official Quits Over Delay on Plan B By Marc Kaufman, Washington Post, September 1, 2005
^ Reuters. "Plan B decision made before analysis finished". MSNBC.com. Retrieved 10 November 2006. {{cite web}}: |author= has generic name (help)
^ "Depositions Indicate Bush Administration Exerted Political Influence on FDA During Plan B Review Process". Center for Reproductive Rights. 2006-08-03. Retrieved 2006-11-10.
^ Announcement on FDA's website
^ New York Times Article 5-22-09
^ Commonwealth of Massachusetts Chapter 91 of the Acts of 2005. "An Act Providing Timely Access to Emergency Contraception." Enacted September 15, 2005. Accessed April 28, 2006.
^ Barragán, Javier L., Hamao, Stephen F., and Trujillo, Alfonsocard L. (2001-09-14). "The Reproductive Health of Refugees". Pontifical Council for the Pastoral Care of Migrants and Itinerant People. Retrieved April 28, 2006.{{cite web}}: CS1 maint: multiple names: authors list (link)
^ "Ethical and Religious Directives for Catholic Health Care Services, Fourth Edition". United States Conference of Catholic Bishops. 2001. Retrieved April 28, 2006.
^ Julie Cantor, J.D., and Ken Baum, M.D. J.D. (2004-11-04). "The Limits of Conscientious Objection - May Pharmacists Refuse to Fill Prescriptions for Emergency Contraception?" (PDF). NEJM. Retrieved 2006-11-13.{{cite web}}: CS1 maint: multiple names: authors list (link)
^ Stein, Rob (2005-03-28). "Pharmacists' Rights at Front Of New Debate". The Washington Post.
^ http://www.medicalnewstoday.com/articles/195070.php
^ Dana Canedy (1999-05-14). "Wal-Mart Decides Against Selling a Contraceptive". New York Times. Retrieved 2006-11-08.
^ Michael Barbaro (2006-03-04). "In Reversal, Wal-Mart Will Sell Contraceptive". New York Times. Retrieved 2007-08-12.
^ http://www.vatican.va/roman_curia/congregations/cfaith/documents/rc_con_cfaith_doc_20081208_dignitas-personae_en.html

Trussell, J., and E. J. Raymond. 2011. Emergency Contraception. (A more recent summary of findings by the same Dr. Trussell whose earlier work is cited above.)

External links

The Emergency Contraception Website (not-2-late.com) – by the Office of Population Research at Princeton University and the Association of Reproductive Health Professionals. Information for women who need emergency contraception now.
Planned Parenthood web site. Educational web site with information for women who need emergency contraception now.
International Consortium for Emergency Contraception Policy-oriented web site directed at professionals.
www.acsa-caah.ca/Portals/
Emergency contraception by the Adolescent Medicine Committee, Canadian Pediatric Society (CPS), Paediatrics and Child Health ACSA-CAAH
The Morning-After Pill: A Well-Kept Secret New York Times, January 10, 1993

[Leung_2010-1] Leung, Vivian W.Y.; Levine, Marc; Soon, Judith A. (2010). "Mechanisms of action of hormonal emergency contraceptives". Pharmacotherapy. 30 (2): 158–168. doi:10.1592/phco.30.2.158. PMID 20099990. {{cite journal}}: |access-date= requires |url= (help); Unknown parameter |month= ignored (help)

[Gemzell-Danielsson_2010-2] Gemzell-Danielsson, Kristina (2010). "Mechanism of action of emergency contraception". Contraception. 82 (5): 404–409. doi:10.1016/j.contraception.2010.05.004. PMID 20933113. {{cite journal}}: |access-date= requires |url= (help); Unknown parameter |month= ignored (help)

[Trussell_2011-3] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Trussell, James; Schwarz, Eleanor Bimla (2011). "Emergency contraception". In Hatcher, Robert A.; Trussell, James; Nelson, Anita L.; Cates, Willard Jr.; Kowal, Deborah; Policar, Michael S. (eds.). Contraceptive technology (20th revised ed.). New York: Ardent Media. pp. 113–145. ISBN 978-1-59708-004-0. ISSN 0091-9721. OCLC 781956734. p. 121:
Mechanism of action
Copper-releasing IUCs
When used as a regular or emergency method of contraception, copper-releasing IUCs act primarily to prevent fertilization. Emergency insertion of a copper IUC is significantly more effective than the use of ECPs, reducing the risk of pregnancy following unprotected intercourse by more than 99%.^2,3 This very high level of effectiveness implies that emergency insertion of a copper IUC must prevent some pregnancies after fertilization.
Emergency contraceptive pills
To make an informed choice, women must know that ECPs—like the birth control pill, patch, ring, shot, and implant,⁷⁶ and even like breastfeeding⁷⁷—prevent pregnancy primarily by delaying or inhibiting ovulation and inhibiting fertilization, but may at times inhibit implantation of a fertilized egg in the endometrium. However, women should also be informed that the best available evidence indicates that ECPs prevent pregnancy by mechanisms that do not involve interference with post-fertilization events.
ECPs do not cause abortion⁷⁸ or harm an established pregnancy. Pregnancy begins with implantation according to medical authorities such as the US FDA, the National Institutes of Health⁷⁹ and the American College of Obstetricians and Gynecologists (ACOG).⁸⁰
Ulipristal acetate (UPA). One study has demonstrated that UP can delay ovulation.⁸¹... Another study found that UPA altered the endometrium, but whether this change would inhibit implantation is unknown.⁸²
p. 122:
Progestin-only emergency contraceptive pills. Early treatment with ECPs containing only the progestin levonorgestrel has been show to impair the ovulatory process and luteal function.^83–87
p. 123:
Combined emergency contraceptive pills. Several clinical studies have shown that combined ECPs containing ethinyl estradiol and levonorgestrel can inhibit or delay ovulation.^107–110

[fr_1997-4] FDA (1997-02-25). "Certain combined oral contraceptives for use as postcoital emergency contraception". Fed Regist. 62 (37): 8610–2.

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[12] Watson PR (1 December 2010). "Watson Launches ella(R)(ulipristal acetate)". Retrieved 12-1-2010. {{cite web}}: Check date values in: |accessdate= (help)

[13] "Planned Parenthood - Mifepristone: Expanding Women's Options for Early Abortion". Retrieved July 23, 2006.

[14] Piaggio G; et al. (2003). "Meta-analysis of randomized trials comparing different doses of mifepristone in emergency contraception". Contraception. 68 (6): 447–52. doi:10.1016/S0010-7824(03)00142-2. PMID 14698075. {{cite journal}}: Unknown parameter |author-separator= ignored (help)

[15] Wertheimer, Randy E. (2000-11-15). "Emergency Postcoital Contraception". American Family Physician. American Academy of Family Physicians. Retrieved 2006-07-23.

[16] Ho; Pak Chung; et al. (2002). "Mifepristone: Contraceptive and Non-Contraceptive Uses". Current Opinions in Obstetrics Gynecology. 14 (3): 325–230. doi:10.1097/00001703-200206000-00013. PMID 12032390. {{cite journal}}: Unknown parameter |author-separator= ignored (help)

[17] Gemzell-Danielsson, K. (2004-06-10). "Mechanisms of action of mifepristone and levonorgestrel when used for emergency contraception". Human Reproduction Update. 10 (4). Oxford University Press: 341–348. doi:10.1093/humupd/dmh027. PMID 15192056. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

[weismiller-18] Weismiller D (2004). "Emergency contraception". Am Fam Physician. 70 (4): 707–14. PMID 15338783. Retrieved 2006-12-01.

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[trussell_1999-20] Trussell J, Rodriguez G, Ellertson C (1999). "Updated estimates of the effectiveness of the Yuzpe regimen of emergency contraception". Contraception. 59 (3): 147–51. doi:10.1016/S0010-7824(99)00018-9. PMID 10382076.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[trussell_2003a-21] Trussell J, Ellertson C, von Hertzen H, Bigrigg A, Webb A, Evans M, Ferden S, Leadbetter C (2003). "Estimating the effectiveness of emergency contraceptive pills". Contraception. 67 (4): 259–65. doi:10.1016/S0010-7824(02)00535-8. PMID 12684144.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[22] <Please add first missing authors to populate metadata.> (1999). "Counsel women to take ECPs as soon as possible". Contracept Technol Update. 20 (7): 75–7. PMID 12295381.

[who_1999-23] WHO/HRP (1999). "Levonorgestrel is more effective, has fewer side-effects, than Yuzpe regimen". Prog Hum Reprod Res (51): 3–5. PMID 12349416.

[WHO_2002-24] von Hertzen, Helena; Piaggio, Gilda; Peregoudov, Alexandre; Ding, Juhong; Chen, Junling; Song, Si; Bártfai, György; Ng, Ernest; Gemzell-Danielsson, Kristina; Oyunbileg, Amindavaa; Wu, Shangchun; Cheng, Weiyu; Lüdicke, Frank; Pretnar-Darovec, Alenka; Kirkman, Rosemary; Mittal, Suneeta; Khomassuridze, Archil; Apter, Dan; WHO Research Group on Post-ovulatory Methods of Fertility Regulation (December 7, 2002). "Low dose mifepristone and two regimens of levonorgestrel for emergency contraception: a WHO multicentre randomised trial". Lancet. 360 (9348): 1803–1810. doi:10.1016/S0140-6736(02)11767-3. PMID 12480356.

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[27] Dixon GW, Schlesselman JJ, Ory HW, Blye RP (1980). "Ethinyl estradiol and conjugated estrogens as postcoital contraceptives". JAMA. 244 (12): 1336–9. doi:10.1001/jama.244.12.1336. PMID 6251288.{{cite journal}}: CS1 maint: multiple names: authors list (link)

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[AAP_2005-31] American Academy of Pediatrics Committee on Adolescence (October 2005). "Emergency contraception". Pediatrics. 116 (4): 1026–1035. doi:10.1542/peds.2005-1877. PMID 16147972.

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[ACOG_2010-33] American College of Obstetricians and Gynecologists (May 2010). "ACOG Practice Bulletin No. 112: Emergency contraception". Obstet Gynecol. 115 (5): 1100–1109. doi:10.1097/AOG.0b013e3181deff2a. PMID 20410799.

[FDA_Plan_B_Rx_to_OTC_switch_med_review-34] FDA Center for Drug Evaluation and Research (August 22, 2006). "Plan B Rx to OTC switch Medical Reviews" (PDF). Beltsville, Md.: Food and Drug Administration. pp. 32–7, 133–77. Retrieved 2006-12-13.

[WHO_MEC_2009-35] WHO Department of Reproductive Health and Research (2009). "Emergency contraceptive pills (ECPs)". Medical eligibility criteria for contraceptive use (PDF) (4th ed.). Geneva: World Health Organization. p. 63. ISBN 978-92-4-156388-8.

[UK_MEC_2009-36] RCOG Faculty of Sexual & Reproductive Healthcare (2009). "UK medical eligibility criteria for contraceptive use" (PDF). London: Royal College of Obstetricians and Gynaecologists. pp. 107–115. Retrieved 2012-04-30. {{cite web}}: |chapter= ignored (help)

[US_MEC_2010-37] CDC Division of Reproductive Health (June 18, 2010). "U.S. Medical eligibility criteria for contraceptive use, 2010" (PDF). MMWR Recomm Rep. 59 (RR-4): 1–86. PMID 20559203.

[Davidoff_2006-38] Davidoff, Frank; Trussell, James (October 11, 2006). "Plan B and the politics of doubt (commentary)". JAMA. 296 (14): 1775–1778. doi:10.1001/jama.296.14.1775. PMID 17032991.

[FSRH_EC_2012-39] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k RCOG Faculty of Sexual & Reproductive Healthcare, Clinical Effectiveness Unit (January 2012). Clinical guidance: emergency contraception (PDF). London: Royal College of Obstetricians and Gynaecologists. ISSN 1755-103X. Retrieved 2012-04-30. p.3:
How does EC work?
In 2002, a judicial review ruled that pregnancy begins at implantation, not fertilisation.⁸ The possible mechanisms of action should be explained to the patient as some methods may not be acceptable, depending on individual beliefs about the onset of pregnancy and abortion.
Copper-bearing intrauterine device (Cu-IUD). Copper is toxic to the ovum and sperm and thus the copper-bearing intrauterine device (Cu-IUD) is effective immediately after insertion and works primarily by inhibiting fertilisation.^9–11 A systematic review on mechanisms of action of IUDs showed that both pre- and postfertilisation effects contribute to efficacy.¹¹ If fertilisation has already occurred, it is accepted that there is an anti-implantation effect,^12,13
Levonorgestrel (LNG). The precise mode of action of levonorgestrel (LNG) is incompletely understood but it is thought to work primarily by inhibition of ovulation.^16,17
Ulipristal acetate (UPA). UPA’s primary mechanism of action is thought to be inhibition or delay of ovulation.²

[FSRH_DI_2012-40] RCOG Faculty of Sexual & Reproductive Healthcare, Clinical Effectiveness Unit (January 2012). Clinical guidance: drug interactions with hormonal contraception (PDF). London: Royal College of Obstetricians and Gynaecologists. ISSN 1755-103X. Retrieved 2012-04-30.

[Trussell_2003b-41] Trussell, James; Hedley, Allison; Raymond, Elizabeth (October 2003). "Ectopic pregnancy following use of progestin-only ECPs (letter)" (PDF). J Fam Plann Reprod Health Care. 29 (4): 249. doi:10.1783/147118903101197944. PMID 14662065.

[WHO_2010-42] UNDP/UNFPA/WHO/World Bank Special Programme of Research, Development and Research Training in Human Reproduction (HRP) (March 25, 2010). "Fact sheet on the safety of levonorgestrel-alone emergency contraceptive pills (LNG ECPs)" (PDF). Geneva: World Health Organization.
Can LNG ECPs cause an abortion?
LNG ECPs do not interrupt an established pregnancy or harm a developing embryo.¹⁵ The evidence available to date shows that LNG ECP use does not prevent a fertilized egg from attaching to the uterine lining. The primary mechanism of action is to stop or disrupt ovulation; LNG ECP use may also prevent the sperm and egg from meeting.¹⁶

[Cleland_2010-43] Cleland, Kelly; Raymond, Elizabeth; Trussell, James; Cheng, Linan; Zhu, Haoping (June 2010). "Ectopic pregnancy and emergency contraceptive pills: a systematic review". Obstet Gynecol. 115 (6): 1263–1266. doi:10.1097/AOG.0b013e3181dd22ef. PMID 20502299.

[WHO_SPR_20-44] WHO Department of Reproductive Health and Research (December 31, 2004). "Question 20. What can a woman do to prevent nausea and vomiting when taking emergency contraceptive pills (ECPs)?". Selected practice recommendations for contraceptive use (2nd ed.). Geneva: World Health Organization. ISBN 92-4-156284-6. {{cite book}}: External link in |chapterurl= (help); Unknown parameter |chapterurl= ignored (|chapter-url= suggested) (help)

[WHO_SPR_21-45] WHO Department of Reproductive Health and Research (December 31, 2004). "Question 21. What can a woman do if she vomits after taking emergency contraceptive pills (ECPs)?". Selected practice recommendations for contraceptive use (2nd ed.). Geneva: World Health Organization. ISBN 92-4-156284-6. {{cite book}}: External link in |chapterurl= (help); Unknown parameter |chapterurl= ignored (|chapter-url= suggested) (help)

[Raymond_2006-46] Raymond, Elizabeth G.; Goldberg, Alisa; Trussell, James; Hays, Melissa; Roach, Elizabeth; Taylor, Douglas (April 2006). "Bleeding patterns after use of levonorgestrel emergency contraceptive pills". Contraception. 73 (4): 376–381. doi:10.1016/j.contraception.2005.10.006. PMID 16531171.

[47] Gainer, Erin; Kenfack, Bruno; Mboudou, Emile; Doh, Anderson Sama; Bouyer, Jean (August 2006). "Menstrual bleeding patterns following levonorgestrel emergency contraception". Contraception. 74 (2): 118–124. doi:10.1016/j.contraception.2006.02.009. PMC 1934349. PMID 16860049.

[48] Gemzell-Danielsson, Kristina; Marions, Lena (July–August 2004). "Mechanisms of action of mifepristone and levonorgestrel when used for emergency contraception". Hum Reprod Update. 10 (4): 341–348. doi:10.1093/humupd/dmh027. PMID 15192056.

[49] Gottardi G, Spreafico A, de Orchi L (1986). "The postcoital IUD as an effective continuing contraceptive method". Contraception. 34 (6): 549–58. doi:10.1016/S0010-7824(86)80011-7. PMID 3549140.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[beyond_coca-cola-50] Ellertson, Charlotte (March/April 1996). "History and Efficacy of Emergency Contraception: Beyond Coca-Cola". Family Planning Perspectives. 28 (2). Guttmacher Institute. Retrieved 2006-11-22. {{cite journal}}: Check date values in: |date= (help)

[51] Chernev T, Ivanov S, Dikov I, Stamenkova R (1995). "Prospective study of contraception with levonorgestrel". Plan Parent Eur. 24 (2): 25. PMID 12290800.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[princeton-52] "Effectiveness of Emergency Contraceptives". The Emergency Contraception Website. Office of Population Research at Princeton University and the Association of Reproductive Health Professionals. 2006. Retrieved 2006-12-02. {{cite web}}: Unknown parameter |month= ignored (help)

[pkjfm-53] Bakhtiar, Saadia (2000). "Contraception". Pakistan Journal of Family Medicine. 11: 19–24. Retrieved 2006-12-02. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)

[princeton2-54] "What is Emergency Contraception?". The Emergency Contraception Website. Office of Population Research at Princeton University and the Association of Reproductive Health Professionals. 2006. Retrieved 2006-12-02. {{cite web}}: Unknown parameter |month= ignored (help)

[55] "Birth Control: The Morning-After Pill". Time. 1966-05-06. Retrieved 2010-05-01.

[56] <Please add first missing authors to populate metadata.> (1967). "Postcoital contraception". IPPF Med Bull. 1 (4): 3. PMID 12254703.

[57] Demers L (1971). "The morning-after pill". N Engl J Med. 284 (18): 1034–6. doi:10.1056/NEJM197105062841813. PMID 5553470.

[58] <Please add first missing authors to populate metadata.> (1973). "FDA considers DES safe as 'morning-after' pill". JAMA. 224 (12): 1581–2. PMID 12257949.

[59] Johnson JH (1984). "Contraception—the morning after". Fam Plann Perspect. 16 (6): 266–270. doi:10.2307/2134916. JSTOR 2134916. PMID 6519238.

[60] Yuzpe A, Thurlow H, Ramzy I, Leyshon J (1974). "Post coital contraception—A pilot study". J Reprod Med. 13 (2): 53–8. PMID 4844513.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[61] Valle G (1975). "The problem of postcoital contraception using oral progestins". Aggiorn Ostet Ginecol. 8 (3): 127–8. PMID 12334868.

[62] <Please add first missing authors to populate metadata.> (1975). "Copper IUD, inserted after coitus averts pregnancy and provides continuing contraceptive protection". Int Fam Plann Dig. 1 (3): 11–2. doi:10.2307/2948217. JSTOR 2948217. PMID 12307393.

[63] "Danazol". Medscape. 2002. Retrieved 2006-11-08.

[64] "Contraception: past, present and future". UK Family Planning Association. 2006. Archived from the original on 2006-09-28. Retrieved 2006-11-09. {{cite web}}: Unknown parameter |month= ignored (help)

[65] FDA (1997). "Certain combined oral contraceptives for use as postcoital emergency contraception". Fed Regist. 62 (37): 8610. {{cite journal}}: Unknown parameter |month= ignored (help) "Since the United Kingdom approved emergency contraceptive pills in 1984, more than 4 million prescriptions have been recorded. However, the actual use is much greater because providers have found it less expensive to provide tablets of identical drugs taken from products packaged as combined oral contraceptives."

[66] "Sponsors". Fertility. 2002. Retrieved 2006-12-01.

[67] Task Force on Postovulatory Methods of Fertility Regulation (1998). "Randomised controlled trial of levonorgestrel versus the Yuzpe regimen of combined oral contraception for emergency contraception". Lancet. 352 (9126): 428–433. doi:10.1016/S0140-6736(98)05145-9. PMID 9708750.

[68] Guillebaud J (1998). "Time for emergency contraception with levonorgestrel alone". Lancet. 352 (9126): 416–417. doi:10.1016/S0140-6736(98)22032-0. PMID 9708743.

[69] "Morning after pill courier service launched". Telegraph. 2012. Retrieved 2012-04-17.

[70] "DrEd and Shutl bring emergency contraception to Londoners within 2 hours" (PDF). Shutl and DrEd. 2012. Retrieved 2012-04-24.

[71] Demers LM (1971). "The morning-after pill". N Engl J Med. 284 (18): 1034–6. doi:10.1056/NEJM197105062841813. PMID 5553470.

[72] Kuchera LK (1971). "Postcoital contraception with diethylstilbestrol". JAMA. 218 (4): 562–3. doi:10.1001/jama.218.4.562. PMID 5171004.

[73] FDA (1973). "Postcoital diethylstilbestrol". FDA Drug Bull. 119 (2): 87–8. PMC 1455105. PMID 18730987. {{cite journal}}: Unknown parameter |month= ignored (help)

[Kennedy_hearing-74] U.S. Senate (1975). Regulation of diethylstilbestrol (DES), 1975: Joint Hearing before the Subcommittee on Health and the Subcommittee on Administrative Practice and Procedure, 94th Congress, 1st Session on S. 963, February 27, 1975. Washington: U.S. Govt. Print. Off.

[proposed73-75] FDA (1973). "Diethylstilbestrol. Use as postcoital contraceptive; patient labeling". Fed Regist. 38 (186): 26809–11. {{cite journal}}: Unknown parameter |month= ignored (help)

[deslabel1975-76] FDA (1975). "Estrogens for oral or parenteral use. Drugs for human use; drug efficacy study; amended notice". Fed Regist. 40 (39): 8242. {{cite journal}}: Unknown parameter |month= ignored (help)

[des25mg1973-77] FDA (1973). "Certain estrogens for oral use. Notice of withdrawal of approval of new drug applications". Fed Regist. 38 (186): 26824–6. {{cite journal}}: Unknown parameter |month= ignored (help)

[dutton-78] Dutton, Diana B. (1988). Worse than the disease: pitfalls of medical progress. Cambridge: Cambridge University Press. ISBN 0-521-34023-3.

[79] FDA (1975). "Diethylstilbestrol as postcoital oral contraceptive; patient labeling". Fed Regist. 40 (25): 5351–5. {{cite journal}}: Unknown parameter |month= ignored (help)

[des25mg1975-80] FDA (1975). "Certain estrogens for oral use or parenteral use. Drugs for human use; drug efficacy study implementation; follow-up notice". Fed Regist. 40 (25): 5384. {{cite journal}}: Unknown parameter |month= ignored (help)

[81] FDA (1978). "DES and Breast Cancer". FDA Drug Bull. 8 (2): 10. {{cite journal}}: Unknown parameter |month= ignored (help)

[82] Hatcher, Robert A.; Stewart, Gary K., Stewart, Felicia; Guest, Felicia; Schwartz, David W.; Jones, Stephanie A. (1980). Contraceptive Technology 1980–1981 (10th ed.). New York: Irvington Publishers. pp. 128–33. ISBN 0-8290-0084-4.{{cite book}}: CS1 maint: multiple names: authors list (link)

[83] Hatcher, Robert A.; Stewart, Gary K., Stewart, Felicia; Guest, Felicia; Josephs, Nancy; Dale, Janet (1982). Contraceptive Technology 1982–1983 (11th ed.). New York: Irvington Publishers. pp. 152–7. ISBN 0-8290-0705-9.{{cite book}}: CS1 maint: multiple names: authors list (link)

[84] Ibarreta, Dolores; Swain, Shanna H. (2001). "The DES story: long-term consequences of prenatal use". In in Harremoës, Poul; Gee, David; Vaz, Sofia Guedes (eds.) (ed.). Late lessons from early warnings: the precautionary principle 1896–2000 (PDF). Copenhagen: European Environmental Agency. pp. 84–92. ISBN 92-9167-323-4. Retrieved 2006-12-07. {{cite book}}: |editor= has generic name (help)CS1 maint: multiple names: authors list (link)

[85] FDA (1997). "Certain combined oral contraceptives for use as postcoital emergency contraception". Fed Regist. 62 (37): 8610–2. {{cite journal}}: Unknown parameter |month= ignored (help)

[86] FDA (1998). "Preven approval package" (PDF). Archived from the original (PDF) on 2006-10-11. Retrieved 2006-12-10. {{cite web}}: Unknown parameter |month= ignored (help)

[87] California Board of Pharmacy (2004). "Pharmacists protocol for dispensing emergency contraception" (PDF). Retrieved 2006-12-10. {{cite web}}: Unknown parameter |month= ignored (help)

[88] FDA (1999). "Plan B approval package". Archived from the original on 2006-10-11. Retrieved 2006-12-10. {{cite web}}: Unknown parameter |month= ignored (help)

[89] FDA (2006). "Plan B information page". Retrieved 2006-12-10. {{cite web}}: Unknown parameter |month= ignored (help)

[90] Barr Pharmaceuticals (2006). "Barr Launches Plan B OTC/Rx Dual-Label Product; Awarded 3 Years New Product Exclusivity". Retrieved 2006-12-12. {{cite web}}: Unknown parameter |month= ignored (help)

[91] Harris, Gardiner (April 22, 2009). "F.D.A. Easing Access to 'Morning After' Pill". The New York Times.

[icechistory-92] International Consortium for Emergency Contraception (ICEC) webpage, section on "History". Accessed 30 November 2006.

[icecproducts-93] ICEC web page, section on "Products and Availability". Accessed 30 November 2006.

[94] "Concept Foundation". Initiative on Public-Private Partnerships for Health. 2006-03-07. Archived from the original on 2006-10-10. Retrieved 2006-11-17. Funding data requires free registration to view.

[95] "IPPF Launches New EC Pill at ICEC Meeting". Consortium News. 2006. Retrieved 2006-11-17. {{cite web}}: Unknown parameter |month= ignored (help)

[96] Glasier A, Baird D (1998). "The effects of self-administering emergency contraception". N Engl J Med. 339 (1): 1–4. doi:10.1056/NEJM199807023390101. PMID 9647872.

[97] Raine T, Harper C, Leon K, Darney P (2000). "Emergency contraception: advance provision in a young, high-risk clinic population". Obstet Gynecol. 96 (1): 1–7. doi:10.1016/S0029-7844(00)00830-9. PMID 10862832.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[98] Jackson RA, Schwarz EB, Freedman L, Darney P (2003). "Advance supply of emergency contraception: effect on use and usual contraception―a randomized trial". Obstet Gynecol. 102 (1): 8–16. doi:10.1016/S0029-7844(03)00478-2. PMID 12850599.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[99] Gold MA, Wolford JE, Smith KA, Parker AM (2004). "The effects of advance provision of emergency contraception on adolescent women's sexual and contraceptive behaviors". J Pediatr Adolesc Gynecol. 17 (2): 87–96. doi:10.1016/j.jpag.2003.11.018. PMID 15050984.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[100] Lo SS, Fan SYS, Ho PC, Glasier AF (2004). "Effect of advanced provision of emergency contraception on women's contraceptive behavior: a randomized controlled trial". Hum Reprod. 19 (10): 2404–10. doi:10.1093/humrep/deh425. PMID 15333602.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[101] Raine TR, Harper CC, Rocca CH, Fischer R, Padian N, Klausner JD, Darney PD (2005). "Direct access to emergency contraception through pharmacies and effect on unintended pregnancy and STIs: a randomized controlled trial". JAMA. 293 (1): 54–62. doi:10.1001/jama.293.1.54. PMID 15632336.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[102] Hu X, Cheng L, Hua X, Glasier A (2005). "Advanced provision of emergency contraception to postnatal women in China makes no difference in abortion rates: a randomized controlled trial". Contraception. 72 (2): 111–6. doi:10.1016/j.contraception.2005.02.004. PMID 16022849.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[103] Belzer M, Sanchez K, Olson J, Jacobs AM, Tucker D (2005). "Advance supply of emergency contraception: a randomized trial in adolescent mothers". J Pediatr Adolesc Gynecol. 18 (5): 347–54. doi:10.1016/j.jpag.2005.06.007. PMID 16202939.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[104] Trussell J, Raymond E, Stewart FH (2006). "Advance supply of emergency contraception: a randomized trial in adolescent mothers (Letter to the editor)". J Pediatr Adolesc Gynecol. 19 (3): 251. doi:10.1016/j.jpag.2006.02.016. PMID 16731424.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[105] Walsh TL, Frezieres RG (2006). "Patterns of emergency contraception use by age and ethnicity from a randomized trial comparing advance provision and information only". Contraception. 74 (2): 110–7. doi:10.1016/j.contraception.2006.02.005. PMID 16860048.

[106] Raymond EG, Stewart F, Weaver M, Monteith C, Van Der Pol B (2006). "Impact of increased access to emergency contraceptive pills: a randomized controlled trial". Obstet Gynecol. 108 (5): 1098–106. doi:10.1097/01.AOG.0000235708.91572.db. PMID 17077230.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[107] Kosunen E, Sihvo S, Hemminki E (1997). "Knowledge and use of hormonal emergency contraception in Finland". Contraception. 55 (3): 153–7. doi:10.1016/S0010-7824(97)00022-X. PMID 9115003.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[108] "Emergency Contraception Doesn't Lower Abortion Rates". Forbes. September 15, 2006. Archived from the original on 2006-10-09. Retrieved 2006-09-23.

[109] Glasier A, Fairhurst K, Wyke S, Zieblad S, Seaman P, Walker J, Lakha F (2004). "Advanced provision of emergency contraception does not reduce abortion rates". Contraception. 69 (5): 36. doi:10.1016/j.contraception.2004.01.002. PMID 15105057. {{cite journal}}: More than one of |pages= and |page= specified (help)CS1 maint: multiple names: authors list (link)

[110] Hu X; et al. (2005). "Advanced provision of emergency contraception to postnatal women in China makes no difference in abortion rates: a randomized controlled trial". Contraception. 72 (2): 111–6. doi:10.1016/j.contraception.2005.02.004. PMID 16022849. {{cite journal}}: Unknown parameter |author-separator= ignored (help)

[fuss-111] Glasier, A (2006). "Emergency contraception: Is it worth all the fuss?". BMJ. 333 (7568): 560–1. doi:10.1136/bmj.38960.672998.80. PMID 16973989.

[112] Glover D eta al (1976). "Diethylstilbestrol in the Treatment of Rape Victims". The Western journal of medicine. 125 (4). West J Med: 331–4. PMC 1237330. PMID 1032235.

[113] Diamond EF (1978). "Physician notes hazards of DES use to prevent pregnancy". Hosp Prog. 59 (3): 6–10. PMID 631811.

[Holmes-114] Holmes MM; et al. (1996). "Rape-related pregnancy: estimates and descriptive characteristics from a national sample of women". Am J Obstet Gynecol. 175 (2): 320–4. doi:10.1016/S0002-9378(96)70141-2. PMID 8765248 Template:Inconsistent citations {{cite journal}}: Unknown parameter |author-separator= ignored (help)CS1 maint: postscript (link)

[115] Stewart, Felicia H. (2000). "Prevention of pregnancy resulting from rape: A neglected preventive health measure". American Journal of Preventive Medicine. 19 (4): 228–229. doi:10.1016/S0749-3797(00)00243-9. PMID 11064225. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)

[Speroff_2011-116] Speroff, Leon; Darney, Philip D. (2011). "Special uses of oral contraception: emergency contraception, the progestin-only minipill". A clinical guide for contraception (5th ed.). Philadelphia: Lippincott Williams & Wilkins. pp. 153–166. ISBN 978-1-60831-610-6. p. 155:
Emergency postcoital contraception
Levonorgestrel
Mechanism and efficacy
There is strong evidence that treatment with emergency contraception acts primarily by preventing or delaying ovulation and by preventing fertilization.^22–26 Studies have indicated that emergency contraception does not prevent implantation.^27–29 Experiments in monkeys and rats could detect no effect of a high dose of levonorgesterel administered postcoitally once fertilization had occurred.^30,31 The evidence indicates that a postfertilization effect does not contribute to the efficacy of emergency contraception.^25,30–33 Clinicians, pharmacists, and patients can be reassured that treatment with emergency contraception is not an abortifacient.
p. 157:
The use of progesterone receptor modulators for emergency contraception
Mifepristone. In randomized trials, 10 mg mifepristone was as effective as 25, 50, or 600 mg. preventing about 80-85% of expected pregnancies (the same efficacy and side effects as with the levonorgestrel method), with a slight decrease in efficacy when treatment was delayed to 5 days after intercourse.^16,52–54
Ulipristal Acetate. Ulipristal acetate (ellaOne) has similar biologic effects as mifepristone and is approved for emergency contraception in Europe and is expected to become available in the U.S.in a single oral dose of 30 mg. Randomized trials demonstrated that ulipristal acetate is slightly more effective than the single 1.5 mg dose of levonorgestrel when used within 72 h after sexual intercourse and even between 72 h and 120h.^55,56 … Progesterone receptor modulators like ulipristal acetate and mifepristone suppress ovarian follicular growth and also delay endometrial maturation, manifested in a delay in menstruation after treatment. Ovulation can be temporarily postponed.
Other methods
Another method of emergency contraception is the insertion of a copper IUD, anytime during the preovulatory phase of the menstrual cycle and up to 5 days after ovulation. The failure rate (in a small number of studies) is very low, 0.1%.^34,35 This method definitely prevents implantation, but it is not suitable for women who are not candidates for intrauterine contraception, e.g., multiple sexual partners or a rape victim. The use of a copper IUD for emergency contraception is expensive, but not if it is retained as an ongoing method of contraception.

[Jensen-117] Jensen, Jeffrey T.; Mishell, Daniel R. Jr. (2012). "Family planning: contraception, sterilization, and pregnancy termination". In Lentz, Gretchen M.; Lobo, Rogerio A.; Gershenson, David M.; Katz, Vern L. (eds.). Comprehensive gynecology. Philadelphia: Mosby Elsevier. pp. 215–272. ISBN 978-0-323-06986-1. {{cite book}}: More than one of |editor= and |editor1-last= specified (help) p. 257:
Emergency contraception
It is believed that the main mechanism of action of high-dose progestin emergency contraception is inhibition of ovulation, but other mechanisms may be involved... Taken together, these data are highly supportive of the concept that levonorgestrel emergency contraception has little or no effect on postovulation events but is highly effective when taken before ovulation. Levonorgestrel emergency contraception does not affect implantation and is not abortifacient.
Intrauterine insertion of a copper IUD within 5 to 10 days of midcycle coitus is a very effective method of preventing continuation of the pregnancy… The LNG-IUS should not be used for emergency contraception.
A study by the WHO reported that use of a single tablet of 10 mg of mifepristone was an effective emergency contraceptive with a pregnancy rate of 1.2%.
Ulipristal, also known as CDB-2914, has been studied as an emergency contraceptive pill… In 2009, European regulatory approval was granted for a 30-mg tablet of ulipristal (under the brand name of EllaOne) as an emergency contraceptive pill for use up to 5 days after unprotected intercourse. An application for approval in the United States is under review.

[Flatow_2012-118] Flatow, Ira (June 15, 2012). "How the morning-after pill works (interview with Kristina Gemzell-Danielsson, MD, Professor and Chair, Division of Obstetrics and Gynecology, Karolinska Institute, Stockholm, Sweden)". Talk of the Nation Science Friday. New York: NPR.

[Belluck_2012b-119] Belluck, Pam (June 6, 2012). "No abortion role seen for morning-after pill". The New York Times. p. A1.
Belluck, Pam (June 6, 2012). "Drug's nickname may have aided politicization". The New York Times. p. A14.

[120] Bayer (March 22, 2010). "Summary of Product Characteristics: Levonelle One Step 1500 mcg; 5.1 Pharmacodynamic properties". London: electronic Medicines Compendium (eMC), Datapharm. The precise mode of action of Levonelle One Step is not known. At the recommended regimen, levonorgestrel is thought to work mainly by preventing ovulation and fertilisation if intercourse has taken place in the preovulatory phase, when the likelihood of fertilisation is the highest. It may also cause endometrial changes that discourage implantation. Levonelle One Step is not effective once the process of implantation has begun.
HRA Pharma (July 19, 2011). "Summary of Product Characteristics: NorLevo 1.5 mg; 5.1 Pharmacodynamic properties". Dublin: Irish Pharmaceutical Healthcare Association. The precise mode of action of Norlevo 1.5 mg is not known. At the used regimen, levonorgestrel is believed to suppress ovulation thus preventing fertilization if the intercourse has taken place in the preovulatory phase when the likelihood of fertilization is the highest. It could also prevent implantation. It is not effective once the process of implantation has begun.

[121] Duramed Pharmaceuticals/Barr Pharmaceuticals (now Teva Women's Health) (July 9, 2010). "Prescribing information: Plan B One-Step; 12.1 Mechanism of action" (PDF). Silver Spring, Md.: FDA Center for Drug Evaluation and Research (CDER). p. 4. Emergency contraceptive pills are not effective if a woman is already pregnant. Plan B One-Step is believed to act as an emergency contraceptive principally by preventing ovulation or fertilization (by altering tubal transport of sperm and/or ova). In addition, it may inhibit implantation (by altering the endometrium). It is not effective once the process of implantation has begun.

[FIGO_2011-122] International Federation of Gynecology and Obstetrics (FIGO) and International Consortium for Emergency Contraception (ICEC) (April 4, 2011). "Mechanism of action: How do levonorgestrel-only emergency contraceptive pills (LNG ECPs) prevent pregnancy?" (PDF). London: International Federation of Gynecology and Obstetrics.
Levonorgestrel-only emergency contraceptive pills:
• Interfere with the process of ovulation;
• May possibly prevent the sperm and the egg from meeting.
Implications of the research:
• Inhibition or delay of ovulation is LNG ECPs principal and possibly only mechanism of action.
• Review of the evidence suggests that LNG ECPs cannot prevent implantation of a fertilized egg. Language on implantation should not be included in LNG ECP product labeling.
• The fact that LNG ECPs have no demonstrated effect on implantation explains why they are not 100% effective in preventing pregnancy, and are less effective the later they are taken. Women should be given a clear message that LNG ECPs are more effective the sooner they are taken.
• LNG ECPs do not interrupt a pregnancy (by any definition of the beginning of pregnancy). However, LNG ECPs can prevent abortions by reducing unwanted pregnancies.

[NYT_2012-123] torial (June 9, 2012). "How morning-after pills really work". The New York Times. p. A20. The F.D.A. now acknowledges that the emerging data suggest the morning-after pill, often called Plan B, does not inhibit implantation. It should remove that unsupported suggestion from the label.

[Cheng_2012-124] Cheng, Linan; Che, Yan; Gülmezoglu, A. Metin (August 15, 2012). "Interventions for emergency contraception". Cochrane Database of Systematic Reviews. 8: CD001324. doi:10.1002/14651858.CD001324.pub4. PMID 22895920.

[Stratton_2010-125] Stratton, Pamela; Levens, Eric D.; Hartog, Beth; Piquion, Johann; Wei, Qingxiang; Merino, Maria; Nieman, Lynnette K. (April 2010). "Endometrial effects of a single early luteal dose of the selective progesterone receptor modulator CDB-2914". Fertility and Sterility. 93 (6): 2035–2041. doi:10.1016/j.fertnstert.2008.12.057. PMC 2911236. PMID 19200989. Post-ovulatory early luteal phase administration of 10–100 mg of ulipristal acetate resulted in a statistically significant dose-dependent 0.6 ± 2.2 mm decrease in endometrial thickness from a baseline of 10.3 ± 2.3 mm to 9.7 ± 1.8 mm (vs. a 1.3 ± 2.3 mm increase in endometrial thickness from a baseline of 10.2 ± 3.2 mm to 11.5 ± 4.1 mm with placebo administration) which the authors hypothesized could hamper implantation.

[126] HRA Pharma (March 15, 2012). "Summary of Product Characteristics: ellaOne 30 mg; 5.1 Pharmacodynamic properties" (PDF). London: European Medicines Agency. p. 7. Ulipristal acetate is an orally-active synthetic selective progesterone receptor modulator which acts via high-affinity binding to the human progesterone receptor. The primary mechanism of action is inhibition or delay of ovulation. Pharmacodynamic data show that even when taken immediately before ovulation is scheduled to occur, ulipristal acetate is able to postpone follicular rupture in some women.

[127] Watson Pharma (under license from HRA Pharma) (May 2, 2012). "Prescribing information: Ella; 12.1 Mechanism of action" (PDF). Silver Spring, Md.: FDA Center for Drug Evaluation and Research (CDER). pp. 4–5. When taken immediately before ovulation is to occur, ella postpones follicular rupture. The likely primary mechanism of action of ulipristal acetate for emergency contraception is therefore inhibition or delay of ovulation; however, alterations to the endometrium that may affect implantation may also contribute to efficacy... The pharmacodynamics of ulipristal acetate depends on the timing of administration in the menstrual cycle. Administration in the mid-follicular phase causes inhibition of folliculogenesis and reduction of estradiol concentration. Administration at the time of the luteinizing hormone peak delays follicular rupture by 5 to 9 days. Dosing in the early luteal phase does not significantly delay endometrial maturation but decreases endometrial thickness by 0.6 ± 2.2 mm (mean ± SD).

[128] "Q&A: The Debate over the Morning-After Pill". NPR. 2006-08-15. Retrieved 2006-11-11.

[129] "Briefing Document (1.2.4 Plan B: Rx-to-OTC Switch)". FDA.gov: December 16, 2003. Accessed August 2, 2006.

[130] "Panel backs over-the-counter 'morning-after' pill". CNN.com. 2003-12-17. Retrieved April 28, 2006.

[131] FDA Official Quits Over Delay on Plan B By Marc Kaufman, Washington Post, September 1, 2005

[reuters-132] Reuters. "Plan B decision made before analysis finished". MSNBC.com. Retrieved 10 November 2006. {{cite web}}: |author= has generic name (help)

[133] "Depositions Indicate Bush Administration Exerted Political Influence on FDA During Plan B Review Process". Center for Reproductive Rights. 2006-08-03. Retrieved 2006-11-10.

[134] Announcement on FDA's website

[135] New York Times Article 5-22-09

[136] Commonwealth of Massachusetts Chapter 91 of the Acts of 2005. "An Act Providing Timely Access to Emergency Contraception." Enacted September 15, 2005. Accessed April 28, 2006.

[137] Barragán, Javier L., Hamao, Stephen F., and Trujillo, Alfonsocard L. (2001-09-14). "The Reproductive Health of Refugees". Pontifical Council for the Pastoral Care of Migrants and Itinerant People. Retrieved April 28, 2006.{{cite web}}: CS1 maint: multiple names: authors list (link)

[138] "Ethical and Religious Directives for Catholic Health Care Services, Fourth Edition". United States Conference of Catholic Bishops. 2001. Retrieved April 28, 2006.

[139] Julie Cantor, J.D., and Ken Baum, M.D. J.D. (2004-11-04). "The Limits of Conscientious Objection - May Pharmacists Refuse to Fill Prescriptions for Emergency Contraception?" (PDF). NEJM. Retrieved 2006-11-13.{{cite web}}: CS1 maint: multiple names: authors list (link)

[140] Stein, Rob (2005-03-28). "Pharmacists' Rights at Front Of New Debate". The Washington Post.

[141] ttp://www.medicalnewstoday.com/articles/195070.php

[142] Dana Canedy (1999-05-14). "Wal-Mart Decides Against Selling a Contraceptive". New York Times. Retrieved 2006-11-08.

[143] Michael Barbaro (2006-03-04). "In Reversal, Wal-Mart Will Sell Contraceptive". New York Times. Retrieved 2007-08-12.

[144] ttp://www.vatican.va/roman_curia/congregations/cfaith/documents/rc_con_cfaith_doc_20081208_dignitas-personae_en.html

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@@ Line 26: / Line 26: @@
 Forms of EC include:
-* Morning after pill = 2 X normal birth control pill to abort unwanted pregnancy day after sex.
 * Emergency contraceptive pills (ECPs)&mdash;sometimes simply referred to as emergency contraceptives (ECs) or the "'''morning-after pill'''"&mdash;are drugs intended to disrupt [[ovulation]] or [[fertilization]], which are steps necessary for pregnancy ([[contraceptives]]).<ref name="Leung 2010">{{cite journal|last1=Leung|first1=Vivian W.Y.|last2=Levine|first2=Marc|last3=Soon|first3=Judith A.|month=February|year=2010|title=Mechanisms of action of hormonal emergency contraceptives|journal=Pharmacotherapy|volume=30|issue=2|pages=158–168|doi=10.1592/phco.30.2.158|pmid=20099990|accessdate=16 March 2011}}</ref><ref name="Gemzell-Danielsson 2010">{{cite journal|last=Gemzell-Danielsson|first=Kristina|month=November|year=2010|title=Mechanism of action of emergency contraception|journal=Contraception|volume=82|issue=5|pages=404–409|doi=10.1016/j.contraception.2010.05.004|pmid=20933113|accessdate=16 March 2011}}</ref><ref name="Trussell 2011">{{cite book|last1=Trussell|first1=James|last2=Schwarz|first2=Eleanor Bimla|year=2011|chapter=Emergency contraception|editor1-last=Hatcher|editor1-first=Robert A.|editor2-last=Trussell|editor2-first=James|editor3-last=Nelson|editor3-first=Anita L.|editor4-last=Cates|editor4-first=Willard Jr.|editor5-last=Kowal|editor5-first=Deborah|editor6-last=Policar|editor6-first=Michael S.|title=Contraceptive technology|edition=20th revised|location=New York|publisher=Ardent Media|isbn=978-1-59708-004-0|issn=0091-9721|oclc=781956734|pages=113–145}} p. 121:<blockquote>Mechanism of action<br/>Copper-releasing IUCs<br/>When used as a regular or emergency method of contraception, copper-releasing IUCs act primarily to prevent fertilization. Emergency insertion of a copper IUC is significantly more effective than the use of ECPs, reducing the risk of pregnancy following unprotected intercourse by more than 99%.<sup>2,3</sup> This very high level of effectiveness implies that emergency insertion of a copper IUC must prevent some pregnancies after fertilization.<br/>Emergency contraceptive pills<br/>To make an informed choice, women must know that ECPs—like the birth control pill, patch, ring, shot, and implant,<sup>76</sup> and even like breastfeeding<sup>77</sup>—prevent pregnancy primarily by delaying or inhibiting ovulation and inhibiting fertilization, but may at times inhibit implantation of a fertilized egg in the endometrium. However, women should also be informed that the best available evidence indicates that ECPs prevent pregnancy by mechanisms that do not involve interference with post-fertilization events.<br/>ECPs do not cause abortion<sup>78</sup> or harm an established pregnancy. Pregnancy begins with implantation according to medical authorities such as the US FDA, the National Institutes of Health<sup>79</sup> and the American College of Obstetricians and Gynecologists (ACOG).<sup>80</sup><br/>''Ulipristal acetate (UPA).'' One study has demonstrated that UP can delay ovulation.<sup>81</sup>... Another study found that UPA altered the endometrium, but whether this change would inhibit implantation is unknown.<sup>82</sup><br/>p. 122:<br/>''Progestin-only emergency contraceptive pills.'' Early treatment with ECPs containing only the progestin levonorgestrel has been show to impair the ovulatory process and luteal function.<sup>83–87</sup><br/>p. 123:<br/>''Combined emergency contraceptive pills.'' Several clinical studies have shown that combined ECPs containing ethinyl estradiol and levonorgestrel can inhibit or delay ovulation.<sup>107–110</sup></blockquote></ref>
 * [[Intrauterine device]]s (IUDs)&mdash;usually used as a primary contraceptive method, but sometimes used as emergency contraception.<ref name="Trussell 2011"/>