|Failure rates (first year)|
|Duration effect||1 day|
|User reminders||Taken within same 3-hour window each day|
|Clinic review||6 months|
|Advantages and disadvantages|
|Weight||No proven effect|
|Period disadvantages||Light spotting may be irregular|
|Period advantages||Often lighter and less painful|
|Unaffected by being on most (but not all) antibiotics. May be used, unlike COCPs, in patients with hypertension and history of migraines. Affected by some anti-epileptics.|
Progestogen-only pills or progestin-only pills (POP) are contraceptive pills that contain only synthetic progestogens (progestins) and do not contain estrogen. They are colloquially known as mini pills.
Although such pills are sometimes called "progesterone-only pills", they do not actually contain progesterone, but one of several chemically related compounds; and there are a number of progestogen-only contraceptive formulations.
The theoretical efficacy is similar to that of the combined oral contraceptive pill (COCP). However, this pill is taken continuously without any breaks between packets, and traditional progestogen-only pills must be taken to a much stricter time every day (within 3 hours vs. a COCP's 12 hours). However, in some countries, the POP desogestrel (Cerazette) has an approved window of 12 hours. The effectiveness is, therefore, dependent upon compliance.
Lacking the estrogen of combined pills, they are not associated with increased risks of deep vein thrombosis or heart disease. With the decreased clotting risk, they are not contraindicated in the setting of sickle-cell disease. The progestin-only pill is recommended over regular birth control pills for women who are breastfeeding because the mini-pill does not affect milk production (estrogen reduces the amount of breast milk). Like combined pills, the minipill decreases the likelihood of pelvic inflammatory disease.
It is unclear whether POPs provide protection against ovarian cancer to the extent that COCPs do.
There are fewer serious complications than with COCPs.
- Desogestrel 75 µg (e.g., Cerazette)
- Drospirenone 4 mg (e.g., Slynd)
- Norethisterone 350 µg (e.g., Micronor, Nor-QD, Noriday)
- Etynodiol diacetate 500 µg (e.g., Femulen)
- Levonorgestrel 30 µg (e.g., 28 mini, Microval, Norgeston)
- Lynestrenol 500 µg (e.g., Exluton, Mini-kare)
- Norethisterone 300 μg (e.g., Mini-Pe)
- Norgestrel 75 µg (or levonorgestrel 37.5 µg) (e.g., Minicon, Neogest, Ovrette)
As well as the following completely discontinued formulations:
- With no break in the dosage, menstrual flow does not initially occur at a predictable time. Most women tend to establish, over a few months, light to heavy spotting at approximately regular intervals.
- May cause mastalgia (breast tenderness, pain) and mood swings, as well as panic attacks, anxiety and depression.
- Some women may experience abdominal cramps and heavy bleeding.
- May cause weight gain.
- No other side effects apart from the ones mentioned above.
Breast cancer risk
Epidemiological evidence on POPs and breast cancer risk is based on much smaller populations of users and so is less conclusive than that for COCPs.
In the largest (1996) reanalysis of previous studies of hormonal contraceptives and breast cancer risk, less than 1% were POP users. Current or recent POP users had a slightly increased relative risk (RR 1.17) of breast cancer diagnosis that just missed being statistically significant. The relative risk was similar to that found for current or recent COCP users (RR 1.16), and, as with COCPs, the increased relative risk decreased over time after stopping, vanished after 10 years, and was consistent with being due to earlier diagnosis or promoting the growth of a preexisting cancer.
The most recent (1999) IARC evaluation of progestogen-only hormonal contraceptives reviewed the 1996 reanalysis as well as 4 case-control studies of POP users included in the reanalysis. They concluded that: "Overall, there was no evidence of an increased risk of breast cancer".
Recent anxieties about the contribution of progestogens to the increased risk of breast cancer associated with HRT in postmenopausal women such as found in the WHI trials have not spread to progestogen-only contraceptive use in premenopausal women.
There is a growing body of research investigating the links between hormonal contraception, such as the progestogen-only pill, and potential adverse effects on women’s psychological health. The findings from a large Danish study of one million women (followed-up from January 2000 to December 2013) were published in 2016, and reported that the use of hormonal contraception, particularly amongst adolescents, was associated with a statistically significant increased risk of subsequent depression. The authors found that women on the progestogen-only pill in particular, were 34% more likely to subsequently take anti-depressants or be given a diagnosis of depression, in comparison with those not on hormonal contraception. In 2018, a similarly large nationwide cohort study in Sweden amongst women aged 12–30 (n=815,662) found an association, particularly amongst young adolescents (aged 12–19), between hormonal contraception and subsequent use of psychotropic drugs. Such studies highlight the need for further research into the influence of hormonal contraception, including the progestogen-only pill on women’s psychological health.
There is some evidence that progestin-only contraceptives may lead to slight weight gain (on average less than 2 kg in the first year) compared to women not using any hormonal contraception.
Mechanism of action
- Very-low-dose progestogen-only contraceptives, such as traditional progestogen-only pills (and subdermal implants Norplant and Jadelle and intrauterine systems Progestasert and Mirena), inconsistently inhibit ovulation in ~50% of cycles and rely mainly on their progestogenic effect of thickening the cervical mucus, thereby reducing sperm viability and penetration.
- Intermediate-dose progestogen-only contraceptives, such as the progestogen-only pill Cerazette (or the subdermal implant Nexplanon), allow some follicular development (part of the steps of ovulation) but much more consistently inhibit ovulation in 97–99% of cycles. The same cervical mucus changes occur as with very-low-dose progestogens.
- High-dose progestogen-only contraceptives, such as the injectables Depo-Provera and Noristerat, completely inhibit follicular development and ovulation. The same cervical mucus changes occur as with very-low-dose and intermediate-dose progestogens.
In anovulatory cycles using progestogen-only contraceptives, the endometrium is thin and atrophic. If the endometrium were also thin and atrophic during an ovulatory cycle, this could, in theory, interfere with implantation of a blastocyst (embryo).
The first POP to be introduced contained 0.5 mg chlormadinone acetate and was marketed in Mexico and France in 1968. However, it was withdrawn in 1970 due to safety concerns pertaining to long-term animal toxicity studies. Subsequently, levonorgestrel 30 µg (brand name Microval) was marketed in Germany in 1971.  It was followed by a number of other POPs shortly thereafter in the early 1970s, including etynodiol diacetate, lynestrenol, norethisterone, norgestrel, and quingestanol acetate. Desogestrel 75 µg (brand name Cerzette) was marketed in Europe in 2002 and was the most recent POP to be introduced. It differs from earlier POPs in that it is able to inhibit ovulation in 97% of cycles.
- Annetine Gelijns (1991). Innovation in Clinical Practice: The Dynamics of Medical Technology Development. National Academies. pp. 172–. NAP:13513.
Development of the minipill, which contains only a progestin, was another result of concerns over the thromboembolic side effects of combination oral contraceptives.36 This development was also driven by the expectation that lower steroid doses would diminish effects on the metabolic and reproductive systems, lessen complaints about nausea and headache, and improve compliance (because it offered a regimen of continuous pill taking rather than the cyclic regimen of earlier pill formulations).37 Syntex was the first to introduce a 0.5 milligram chlor- madinone acetate minipill in 1968 in France, although this pill was withdrawn from the market in 1970 when long-term animal toxicity tests for the FDA revealed the occurrence of breast nodules in beagles.38 Nevertheless, other manufacturers began to pursue minipill development using their own progestogens, and since 1970 a variety of compounds have been introduced.
- Bennett, John P. (1974). "The Second Generation of Hormonal Contraceptives". Chemical Contraception. pp. 39–62. doi:10.1007/978-1-349-02287-8_4. ISBN 978-1-349-02289-2.
Chlormadinone acetate was the first minipill contraceptive to be marketed, in Mexico during July 1968. This compound was removed from clinical use in February 1970 because it produced nodules in the breast tissues of beagle dogs [...]
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- Population Reports: Oral contraceptives. Department of Medical and Public Affairs, George Washington Univ. Medical Center. 1975. p. A-64.
Distribution and Use of the Minipill. [...] Progestogen & Dose in mg: d-Norgestrel 0.03. Manufacturer: Schering AG. Brand Names: Microlut, Nordrogest. Where & When First Marketed: Federal Republic of Germany 1971.
- "Drugs@FDA: FDA Approved Drug Products". United States Food and Drug Administration. Retrieved 6 January 2018.
- Collaborative Group on Hormonal Factors in Breast Cancer (1996). "Breast cancer and hormonal contraceptives: collaborative reanalysis of individual data on 53,297 women with breast cancer and 100,239 women without breast cancer from 54 epidemiological studies". Lancet. 347 (9017): 1713–27. doi:10.1016/S0140-6736(96)90806-5. PMID 8656904. Archived from the original on 2019-01-23. Retrieved 2019-08-17.
- Collaborative Group on Hormonal Factors in Breast Cancer (1996). "Breast cancer and hormonal contraceptives: further results". Contraception. 54 (3 Suppl): 1S–106S. doi:10.1016/s0010-7824(15)30002-0. PMID 8899264.
- IARC Working Group on the Evaluation of Carcinogenic Risks to Humans (1999). "Hormonal contraceptives, progestogens only". Hormonal contraception and post-menopausal hormonal therapy; IARC monographs on the evaluation of carcinogenic risks to humans, Volume 72. Lyon: IARC Press. pp. 339–397. ISBN 92-832-1272-X.
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- Glasier, Anna (March 20, 2015). "Chapter 134. Contraception". In Jameson, J. Larry; De Groot, Leslie J.; de Krester, David; Giudice, Linda C.; Grossman, Ashley; Melmed, Shlomo; Potts, John T., Jr.; Weir, Gordon C. (eds.). Endocrinology: Adult and Pediatric (7th ed.). Philadelphia: Saunders Elsevier. p. 2306. ISBN 978-0-323-18907-1.
- Zettermark, Sofia; Vicente, Raquel Perez; Merlo, Juan (2018-03-22). "Hormonal contraception increases the risk of psychotropic drug use in adolescent girls but not in adults: A pharmacoepidemiological study on 800 000 Swedish women". PLOS ONE. 13 (3): e0194773. doi:10.1371/journal.pone.0194773. ISSN 1932-6203. PMC 5864056. PMID 29566064.
- Skovlund, Charlotte Wessel; Mørch, Lina Steinrud; Kessing, Lars Vedel; Lidegaard, Øjvind (2016-11-01). "Association of Hormonal Contraception With Depression". JAMA Psychiatry. 73 (11): 1154–1162. doi:10.1001/jamapsychiatry.2016.2387. ISSN 2168-6238. PMID 27680324.
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Ovulation may be suppressed in 15–40% of cycles by POPs containg levonorgestrel, norethisterone, or etynodiol diacetate, but in 97–99% by those containing desogestrel.
- Greenberg (19 February 2016). Exploring the Dimensions of Human Sexuality. Jones & Bartlett Learning. pp. 481–. ISBN 978-1-284-11474-4.
The progestin-only pill was introduced in 1972.
- Amy Whitaker; Melissa Gilliam (27 June 2014). Contraception for Adolescent and Young Adult Women. Springer. pp. 26, 97. ISBN 978-1-4614-6579-9.
- Kathy French (9 November 2009). Sexual Health. John Wiley & Sons. pp. 92–93. ISBN 978-1-4443-2257-6.
- J. Larry Jameson; Leslie J. De Groot (18 May 2010). Endocrinology - E-Book: Adult and Pediatric. Elsevier Health Sciences. pp. 2424–. ISBN 978-1-4557-1126-0.
In 2002, a POP containing desogestrel 75 ug/day, a dose sufficient to inhibit ovulation in almost every cycle, was introduced in Europe.51