Sexual intercourse, or copulation or coitus, is the insertion and thrusting of a male's penis into a female's vagina for the purposes of sexual pleasure or reproduction. Other forms of penetrative sexual intercourse include anal sex, oral sex, fingering, and use of a strap-on dildo.
Sexual intercourse commonly contributes to human bonding, usually being used solely for pleasure and often leading to stronger emotional bonds, and there are a variety of views concerning what constitutes sexual intercourse or other sexual activity. For example, non-penetrative sex (such as non-penetrative cunnilingus) has been referred to as "outercourse", but may also be among the sexual acts contributing to human bonding and considered sexual intercourse. The term sex, often a shorthand for sexual intercourse, can mean any form of sexual activity. Because individuals can be at risk of contracting sexually transmitted infections during these activities, though the transmission risk is significantly reduced during non-penetrative sex, safe sex practices are advised.
In human societies, some jurisdictions have placed various restrictive laws against certain sexual activities, such as sex with minors, incest, extramarital sex, position-of-trust sex, prostitution, sodomy, public lewdness, rape, and zoophilia. Religious beliefs can play a role in decisions about sex, or its purpose, as well; for example, beliefs about what sexual acts constitute virginity loss or the decision to make a virginity pledge. Some sections of Christianity commonly view sexual activity between a married couple for the purpose of reproduction as holy, while other sections may not. Modern Judaism and Islam view sexual intercourse between husband and wife as a spiritual and edifying action. Hinduism and Buddhism views on sexuality have differing interpretations.
Sexual intercourse between non-human animals is more often termed copulation; for most non-human mammals, mating and copulation occur at the point of estrus (the most fertile period of time in the female's reproductive cycle), which increases the chances of successful impregnation. However, bonobos, dolphins, and chimpanzees are known to engage in sexual intercourse even when the female is not in estrus, and to engage in sex acts with same-sex partners. Like humans engaging in sexual activity primarily for pleasure, this behavior in the aforementioned animals is also presumed to be for pleasure, and a contributing factor to strengthening their social bonds.
Etymology and definitions
Behaviors termed sexual intercourse may be described and defined by different terms, including copulation, coitus or coition; the term coitus is derived from the Latin word coitio or coire, meaning "a coming together or joining together" or "to go together" and is usually defined as penile-vaginal penetration. Penetration by the hardened, erect penis is additionally known as intromission, or by the Latin name immissio penis (Latin for "insertion of the penis"). Copulation, though usually used to describe the mating process of non-human animals, is defined as the sexually reproductive act of transferring sperm from a male to a female or sexual procreation between a man and a woman. As such, common vernacular and research often limit sexual intercourse to penile-vaginal penetration, with virginity loss based on the activity. By comparison, the term sex and the phrase "having sex" commonly mean any sexual activity – penetrative and non-penetrative. The World Health Organization states that non-English languages and cultures use different terms for sexual activity, with slightly different meanings. Various vulgar or slang words and euphemisms are also used to describe sexual intercourse or other sexual activity, such as the term fuck and the phrase "sleeping together".
Researchers have been described as usually defining sexual intercourse as penile-vaginal intercourse, while using specific terms (such as anal sex or oral sex) for other sexual activities, but also as "rarely disclos[ing] how they define sex or even whether they resolved potential discrepancies in definitions of sex". Researchers' focus on penile-vaginal intercourse has been attributed to "the larger culture's preoccupation with this form of sexual activity," and a concern is that the "widespread, unquestioned equation of penile-vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question [about sexual activity] matches what the researcher had in mind'". This focus also regulates other forms of mutual sexual activity to foreplay or regards them as not being "real sex" and additionally limits how rape is defined. Additional concern is that the "conceptual conflation of sex, vaginal intercourse, and sexual function results in less knowledge about the range of sexual behaviors that participants engage in" and "limit[s] the generalizability of research for nonheterosexual participants and/or those individuals who are not engaging in heterosexual sexual intercourse".
Anal sex, oral sex and fingering may be regarded as sexual intercourse, or, along with non-penetrative sex acts, as maintaining "technical virginity"; they may also be regarded as "outercourse" regardless of any penetrative aspects. Heterosexual couples may engage in anal or oral sex not only for sexual pleasure, but as ways of maintaining that they are virgins because they have not engaged in the reproductive act of penile-vaginal intercourse. Similarly, some gay men consider frotting or oral sex as ways of maintaining their virginities, with anal penetration defined as sexual intercourse and resulting in the losses of their virginities, while other gay men define frotting or oral sex as their main forms of sexual intercourse. Lesbians may define oral sex or fingering as sexual intercourse and resulting in the losses of their virginities, and may also regard tribadism as a primary form of sexual activity.
In 1999, a study by the Kinsey Institute examined the definition of sex based on a 1991 random sample of 599 college students from 29 U.S. states; it reported that while "virtually every college student they surveyed considered penile-vaginal intercourse to be sex," and only 19–20% said that anal intercourse was not sex, 60% said oral-genital contact (fellatio, cunnilingus) did not constitute having sex. Similarly, a 2003 study published in the Canadian Journal of Human Sexuality focusing on definitions of having sex and noting studies concerning university students from the United States, the United Kingdom, and Australia reported that "[w]hile the vast majority of respondents (more than 97%) in these three studies included penile-vaginal intercourse in their definition of sex, fewer (between 70% and 90%) respondents considered penile-anal intercourse to constitute having sex" and that "oral-genital behaviours were defined as sex by between 32% and 58% of respondents".
A different study by the Kinsey Institute sampled 484 people, ranging in ages 18–96. The study reported that nearly 95% of its participants "agreed that penile-vaginal intercourse meant 'had sex.' But the numbers changed as the questions got more specific". 11 percent of respondents based "had sex" on whether the man had achieved an orgasm, concluding that absence of an orgasm does not constitute "having had" sex. "About 80 percent of respondents said penile-anal intercourse meant 'had sex.' About 70 percent of people believed oral sex was sex."
Variation and stimulation factors
Sexual intercourse or other sexual activity can encompass various sexual behaviors, including different sex positions or the use of sex toys. Foreplay may precede particular sexual activities, and often leads to sexual arousal of the partners, resulting in the erection of the penis or (usually) natural lubrication of the vagina.
During coitus, the partners move their hips to move the penis backward and forward inside the vagina to cause friction, typically without fully removing the penis. In this way, they stimulate themselves and each other, often continuing until orgasm in either or both partners is achieved.
For human females, stimulation of the clitoris plays a significant role in sexual activity; 70–80% of women require direct clitoral stimulation to achieve orgasm, though indirect clitoral stimulation (for example, via vaginal intercourse) may also be sufficient (see orgasm in females). Because of this, some couples may engage in the woman on top position or the coital alignment technique, a technique combining the "riding high" variation of the missionary position with pressure-counterpressure movements performed by each partner in rhythm with sexual penetration, to maximize clitoral stimulation.
Anal sex involves stimulation of the anus, anal cavity, sphincter valve or rectum; it most commonly involves the insertion of a man's penis into another person's rectum, but pegging, use of other sex toys or fingers, to penetrate the anus, and anilingus, are also anal sex.
Oral sex consists of all the sexual activities that involve the use of the tongue, rest of the mouth and throat to stimulate genitalia or anus. It is sometimes performed to the exclusion of all other forms of sexual activity, and may include the ingestion or absorption of semen or vaginal fluids.
Fingering is the manual (genital) manipulation of the clitoris, rest of the vulva, vagina, or anus for the purpose of sexual arousal and sexual stimulation. It may constitute the entire sexual encounter or it may be part of mutual masturbation, foreplay or other sexual activities.
Bonding and affection
In animals, copulation ranges from a purely reproductive activity to one of emotional bonding between mated pairs. Sexual intercourse and other sexual activity typically play a strong role in human bonding. For example, in many societies, it is normal for couples to have frequent intercourse while using some method of birth control (contraception), sharing pleasure and strengthening their emotional bond through sexual activity even though they are deliberately avoiding pregnancy.
In humans and bonobos, the female undergoes relatively concealed ovulation so that both male and female partners commonly do not know whether she is fertile at any given moment. One possible reason for this distinct biological feature may be formation of strong emotional bonds between sexual partners important for social interactions and, in the case of humans, long-term partnership rather than immediate sexual reproduction.
Humans, bonobos, dolphins, and chimpanzees are all intelligent social animals, whose cooperative behavior proves significantly more successful than that of any individual alone. In these animals, the use of sex has evolved beyond reproduction, to apparently serve additional social functions. Sex reinforces intimate social bonds between individuals to form larger social structures. The resulting cooperation encourages collective tasks that promote the survival of each member of the group.
Duration and sexual difficulties
Sexual intercourse often ends when the man has ejaculated, and thus the partner might not have time to reach orgasm. In addition, premature ejaculation (PE) is common, and women often require a substantially longer duration of stimulation with a sexual partner than men do before reaching an orgasm. Masters and Johnson found that men took approximately 4 minutes to reach orgasm with their partners; women took approximately 10–20 minutes to reach orgasm with their partners, but 4 minutes to reach orgasm when they masturbated. Scholars state "many couples are locked into the idea that orgasms should be achieved only through intercourse [vaginal sex]" and that "[e]ven the word foreplay suggests that any other form of sexual stimulation is merely preparation for the 'main event.'... ...Because women reach orgasm through intercourse less consistently than men, they are more likely than men to have faked an orgasm".
In 1991, scholars from the Kinsey Institute stated, "The truth is that the time between penetration and ejaculation varies not only from man to man, but from one time to the next for the same man." They added that the appropriate length for intercourse is the length of time it takes for both partners to be mutually satisfied, emphasizing that Kinsey "found that 75 percent of men ejaculated within two minutes of penetration. But he didn't ask if the men or their partners considered two minutes mutually satisfying" and "more recent research reports slightly longer times for intercourse". A 2008 survey of Canadian and American sex therapists stated that the average time for intromission was 7 minutes and that 1 to 2 minutes was too short, 3 to 7 minutes was adequate and 7 to 13 minutes desirable, while 10 to 30 minutes was too long.
Anorgasmia is regular difficulty reaching orgasm after ample sexual stimulation, causing personal distress. This is significantly more common in women than in men. The physical structure of the act of coitus favors penile stimulation over clitoral stimulation. The location of the clitoris then usually necessitates manual stimulation in order for the female to achieve orgasm. Approximately 15% of women report difficulties with orgasm, 10% have never climaxed, and 40–50% have either complained about sexual dissatisfaction or experienced difficulty becoming sexually aroused at some point in their lives. A 1994 Laumann study reported that 75% of men and 29% of women always have orgasms with their partner.
Vaginismus is the involuntary tensing of the pelvic floor musculature, making coitus, or any form of penetration of the vagina, distressing, painful, and sometimes impossible for women. It is a conditioned reflex of the pubococcygeus muscle, and is sometimes referred to as the "PC muscle". Vaginismus can be a vicious cycle for women; they expect to experience pain during sexual intercourse, which then causes a muscle spasm, which leads to painful sexual intercourse. Treatment of vaginismus often includes both psychological and behavioral techniques, including the use of vaginal dilators. Additionally, the use of Botox as a medical treatment for vaginismus has been tested. Some women also experience dyspareunia, a medical term specifically for painful or uncomfortable sexual intercourse.
Approximately 40% of males suffer from some form of erectile dysfunction (ED) or impotence, at least occasionally. For those whose impotence is caused by medical conditions, prescription drugs such as Viagra, Cialis, and Levitra are available. However, doctors caution against the unnecessary use of these drugs because they are accompanied by serious risks such as increased chance of heart attack. Moreover, using a drug to counteract the symptom—impotence—can mask the underlying problem causing the impotence and does not resolve it. A serious medical condition might be aggravated if left untreated.
Premature ejaculation is more common than erectile dysfunction. "Estimates vary, but as many as 1 out of 3 men may be affected by [premature ejaculation] at some time." "Masters and Johnson speculated that premature ejaculation is the most common sexual dysfunction, even though more men seek therapy for erectile difficulties." This is because "although an estimated 15 percent to 20 percent of men experience difficulty controlling rapid ejaculation, most do not consider it a problem requiring help, and many women have difficulty expressing their sexual needs". The American Urological Association (AUA) estimates that premature ejaculation could affect 21 percent of men in the United States. The Food and Drug Administration (FDA or USFDA) has examined the drug dapoxetine to treat premature ejaculation. In clinical trials, those with PE who took dapoxetine experienced sexual intercourse three to four times longer before orgasm than without the drug. Another ejaculation-related disorder is delayed ejaculation, which can be caused as an unwanted side effect of antidepressant medications such as Fluvoxamine.
Though disability-related pain and mobility impairment can hamper sexual intercourse, in many cases, the most significant impediments to sexual intercourse for individuals with a disability are psychological. In particular, people who have a disability can find sexual intercourse daunting due to issues involving their self-concept as a sexual being, or a partner's discomfort or perceived discomfort. Temporary difficulties can arise with alcohol and sex, as alcohol initially increases interest (through disinhibition) but decreases capacity with greater intake.
Reproduction, reproductive methods and pregnancy
Reproduction among humans usually occurs with penile-vaginal penetration. Male orgasm usually includes ejaculation, a series of muscular contractions that deliver semen containing male gametes known as sperm cells or spermatozoa from the penis into the vagina. The subsequent route of the sperm from the vault of the vagina is through the cervix and into the uterus, and then into the fallopian tubes. Millions of sperm are present in each ejaculation, to increase the chances of one fertilizing an egg or ovum (see sperm competition). When a fertile ovum from the female is present in the fallopian tubes, the male gamete joins with the ovum, resulting in fertilization and the formation of a new embryo. When a fertilized ovum reaches the uterus, it becomes implanted in the lining of the uterus – known as the endometrium – and a pregnancy begins. Unlike most species, human sexual activity is not linked to periods of estrus and can take place at any time during the reproductive cycle, even during pregnancy. Where a sperm donor has sexual intercourse with a woman who is not his partner, for the sole purpose of impregnating the woman, this may be known as natural insemination, as opposed to artificial insemination. However, most sperm donors donate their sperm through a sperm bank and pregnancy is achieved through artificial insemination. Artificial insemination is performed with the express intention of attempting to impregnate the female, and, to this extent, its purpose is the medical equivalent of sexual intercourse.
In 2005, the World Health Organization (WHO) estimated that 123 million women become pregnant world-wide each year, and around 87 million of those pregnancies or 70.7% are unintentional. Approximately 46 million pregnancies per year reportedly end in induced abortion. Approximately 6 million U.S. women become pregnant per year. Out of known pregnancies, two-thirds result in live births and roughly 25% in abortions; the remainder end in miscarriage. However, many more women become pregnant and miscarry without even realizing it, instead mistaking the miscarriage for an unusually heavy menstruation. The U.S. teenage pregnancy rate fell by 27 percent between 1990 and 2000, from 116.3 pregnancies per 1,000 girls aged 15–19 to 84.5. This data includes live births, abortions, and fetal losses. Almost 1 million American teenage women, 10% of all women aged 15–19 and 19% of those who report having had intercourse, become pregnant each year. Britain has been stated to have a teenage pregnancy rate similar to America's.
Reproductive methods and pregnancy also extend to gay and lesbian couples. For gay male pairings, there is the option of surrogate pregnancy; for lesbian couples, there is donor insemination in addition to choosing surrogate pregnancy. Further, developmental biologists have been researching and developing techniques to facilitate biological same-sex reproduction, though this has yet to be demonstrated in humans (see same-sex reproduction). Surrogacy and donor insemination remain the primary methods. Surrogacy is an arrangement in which a woman carries and delivers a child for another couple or person. The woman may be the child's genetic mother (traditional surrogacy) or she may carry a pregnancy to delivery after having another woman's eggs transferred to her uterus (gestational surrogacy). Gay or lesbian pairings who want the host to have no genetic connection to the child may choose gestational surrogacy and enter into a contract with an egg donor. Gay male couples might decide that they should both contribute semen for the in vitro fertilisation (IVF) process, which further establishes the couple's joint intention to become parents. Lesbian couples often have contracts drafted to extinguish the legal rights of the sperm donor, while creating legal rights for the parent who is not biologically related to the child.
Safe sex and contraception
There are a variety of safe sex practices, including non-penetrative sex acts, and heterosexual couples may use oral or anal sex (or both) as a means of birth control (contraception). Safe sex is a relevant harm reduction philosophy, and condoms are used as a form of safe sex and contraception. Condoms and dental dams are widely recommended for the prevention of sexually transmitted infections (STIs). According to reports by the National Institutes of Health (NIH) and World Health Organization (WHO), correct and consistent use of latex condoms reduces the risk of HIV/AIDS transmission by approximately 85–99% relative to risk when unprotected.
Decisions and options concerning birth control can be affected by cultural reasons, such as religion, gender roles or folklore. In the predominantly Catholic countries Ireland, Italy and the Philippines, fertility awareness and the rhythm method are emphasized while disapproval is expressed with regard to other contraceptive methods. Worldwide, sterilization is a more common birth control method, and use of the intrauterine device (IUD) is the most common and effective way of reversing contraception. Conception and contraception are additionally a life-and-death situation in developing countries, where one in three women give birth before age 20; however, 90 percent of unsafe abortions in these countries could be prevented by effective contraception use.
In 2004, the Guttmacher Institute indicated in 2002 that 62% of the 62 million women aged 15–44 are currently using a contraceptive method, that among U.S. women who practice contraception, the Pill is the most popular choice (30.6%), followed by tubal sterilization (27.0%) and the male condom (18.0%), and that 27% of teenage women using contraceptives choose condoms as their primary method. A 2006 Kaiser Family Foundation report stated that among sexually active 15- to 19-year-olds in the U.S., 83% of females and 91% of males reported using at least one method of birth control during last intercourse.
The National Survey of Sexual Health and Behavior (NSSHB) indicated in 2010 that 1 of 4 acts of vaginal intercourse are condom-protected in the U.S. (1 in 3 among singles), condom use is higher among black and Hispanic Americans than among white Americans and those from other racial groups, and adults using a condom for intercourse were just as likely to rate the sexual extent positively in terms of arousal, pleasure and orgasm than when having intercourse without one.
Prevalence of sexual activity
In 2003, Michael Bozon of the French Institut national d'études démographiques conducted a cross-cultural study titled At what age do women and men have their first sexual intercourse?. In the first group of the contemporary cultures he studied, which included sub-Saharan Africa (listing Mali, Senegal and Ethiopia), the data indicated that the age of men at sexual initiation in these societies is at later ages than that of women, but is often extra-marital; the study considered the Indian subcontinent to also fall into this group, though data was only available from Nepal. In the second group, the data indicated families encouraged daughters to delay marriage, and to abstain from sexual activity before that time. However, sons are encouraged to gain experience with older women or prostitutes before marriage. Age of men at sexual initiation in these societies is at lower ages than that of women; this group includes Latin cultures, both from southern Europe (Portugal, Greece and Romania are noted) and from Latin America (Brazil, Chile, and the Dominican Republic). The study considered many Asian societies to also fall into this group, although matching data was only available from Thailand. In the third group, age of men and women at sexual initiation was more closely matched; there were two sub-groups, however. In non-Latin, Catholic countries (Poland and Lithuania are mentioned), age at sexual initiation was higher, suggesting later marriage and reciprocal valuing of male and female virginity. The same pattern of late marriage and reciprocal valuing of virginity was reflected in Singapore and Sri Lanka. The study considered China and Vietnam to also fall into this group, though data were not available. In northern and eastern European countries, age at sexual initiation was lower, with both men and women involved in sexual activity before any union formation; the study listed Switzerland, Germany and the Czech Republic as members of this group.
According to a survey conducted in the United States by the 1995 National Survey of Adolescent Men and the 1995 National Survey of Family Growth, at least 3/4 of all men and women in the U.S. engaged in sexual intercourse by their late teenage years, and more than 2/3 of all sexually experienced teens had two or more partners. Based on the 2002 National Survey of Family Growth, published by the U.S. Department of Health and Human Services, the average age of first sexual intercourse in U.S. participants aged 15 to 44 was 17.3 years for females and 17.0 years for males. Special tabulations by the National Center for Health Statistics suggest that this figure has changed between 2006 and 2010 to 17.1 years for both males and females. The Centers for Disease Control and Prevention (CDC) stated that 45.5 percent of girls and 45.7 percent of boys had engaged in sexual activity by 19 in 2002; in 2011, reporting their research from 2006–2010, the CDC stated that 43% of American unmarried teenage girls and 42% of American unmarried teenage boys have ever engaged in sexual intercourse. The CDC also reports that American girls will most likely lose their virginity to a boy who is 1 to 3 years older than they are.
According to the U.S. Department of Health and Human Services, teenagers are delaying sex until older ages. Between 1988 and 2002, the percentage of people in the U.S. who have had intercourse between the ages of 15 to 19 fell from 60 to 46 percent for males, and from 51 to 46 percent for females. Additionally, a 2006 survey conducted by The Observer suggested that most adolescents in Britain were waiting longer to have sexual intercourse than they were only a few years earlier. In 2002, it was reported that 32% of British teenagers were having sex before the age of 16, while, in 2006, it was only 20%. The average age a British teenager lost his/her virginity was reportedly 17.13 years in 2002; in 2006, it was 17.44 years on average for girls and 18.06 for boys. The most notable drop among teens who reported having sex was 14- and 15-year-olds. A 2008 survey conducted by YouGov for Channel 4 suggested that 40% of all 14- to 17-year-olds are sexually active, 74% of sexually active 14- to 17-year-olds have had a sexual experience under the age of consent, and 6% of teens would wait until marriage before having sex.
In humans, sexual activity has been reported to produce health benefits as varied as improved sense of smell, stress and blood pressure reduction, increased immunity, and decreased risk of prostate cancer. Sexual intimacy, as well as orgasms, increases levels of the hormone oxytocin, also known as "the love hormone", which helps people bond and build trust. Sexual activity is also known as one of many mood repair strategies, which means it can be used to help dissipate feelings of sadness or depression. A long-term study of 3,500 people between 30 and 101 by clinical neuropsychologist David Weeks, head of old age psychology at the Royal Edinburgh Hospital in Scotland, found that "sex helps you look between four and seven years younger", according to impartial ratings of the subjects' photographs. Exclusive causation, however, is unclear, and the benefits may be indirectly related to sex and directly related to significant reductions in stress, greater contentment, and better sleep that sex promotes.
Sexually transmitted infections (STIs) can be spread by person-to-person sexual contact, especially penetrative sexual intercourse. There are 19 million new cases of sexually transmitted infections every year in the U.S., and, in 2005, the World Health Organization estimated that 448 million people aged 15–49 were being infected a year with curable STIs such as syphilis, gonorrhea and chlamydia. In 2006, The Independent newspaper reported that the biggest rise in sexually transmitted infections was in syphilis, which rose by more than 20%, while increases were also seen in cases of genital warts and herpes.
STIs are caused by bacteria, viruses and parasites, which are passed from person to person during sexual contact. Some, in particular HIV and syphilis, can also be passed in other ways, including from mother to child during pregnancy and childbirth, through blood products, and by shared hypodermic needles. Gonococcal or chlamydial infections often produce no symptoms. Untreated chlamydial infection can lead to female infertility and ectopic pregnancy. Human papillomavirus can lead to genital and cervical cancers. Syphilis can result in stillbirths and neonatal deaths. Untreated gonococcal infections result in miscarriages, preterm births and perinatal deaths. Infants born to mothers with untreated gonorrhoea or chlamydia can develop serious eye infections, which can lead to blindness. Hepatitis B can also be transmitted through sexual contact. Globally, there are about 350 million chronic carriers of hepatitis B.
Some STIs can cause ulceration, and, even if they do not, they increase the risk of both acquiring and passing on HIV up to ten-fold. HIV is one of the world's leading infectious killers, and, in 2010, approximately 30 million people were estimated to have died because of it since the beginning of the epidemic. Of the 2.7 million new HIV infections estimated to occur worldwide in 2010, 1.9 million (70%) were in Africa. "The estimated 1.2 million Africans who died of HIV-related illnesses in 2010 comprised 69% of the global total of 1.8 million deaths attributable to the epidemic." It is diagnosed by blood tests, and while no cure has been found, it can be controlled with antiretroviral drugs, and patients can enjoy healthy and productive lives.
The most effective way to avoid sexually transmitted infections is to abstain from sexual intercourse, including vaginal, anal, and oral sex, or to have sexual intercourse only with one long-term, uninfected partner who also remains entirely monogamous. The World Health Organization states, "Male latex condoms, when used consistently and correctly, are highly effective in reducing the transmission of HIV and other sexually transmitted infections, including gonorrhoea, chlamydial infection and trichomoniasis." In cases where infection is suspected, early medical intervention is highly beneficial in all cases.
Sexual activity can directly cause death, particularly due to coronary circulation complications, which is sometimes termed a coital coronary; people, especially those who get little or no physical exercise, have a slightly increased risk of triggering a heart attack or sudden cardiac death when they engage in sexual intercourse or any vigorous physical exercise that is engaged in on a sporadic basis. Increased risk is temporary with incidents occurring within a few hours of the activity. Regular exercise reduces, but does not eliminate, the increased risk.
Some researchers, such as Alex Comfort, posit three potential advantages of sexual intercourse in humans, which are not mutually exclusive: reproductive, relational, and recreational. While the development of the birth-control pill and other highly effective forms of contraception in the mid- and late 20th century increased people's ability to segregate these three functions, they still overlap a great deal and in complex patterns. For example: A fertile couple may have sexual intercourse while contracepting not only to experience sexual pleasure (recreational), but also as a means of emotional intimacy (relational), thus deepening their bonding, making their relationship more stable and more capable of sustaining children in the future (deferred reproductive). This same couple may emphasize different aspects of sexual intercourse on different occasions, being playful during one episode of intercourse (recreational), experiencing deep emotional connection on another occasion (relational), and later, after discontinuing contraception, seeking to achieve pregnancy (reproductive, or more likely reproductive and relational).
Nearly all Americans marry during their lifetime; yet close to half of all first marriages are expected to end in separation or divorce, many within a few years, and subsequent marriages are even more likely to end. Sexual dissatisfaction is associated with increased risk of divorce and relationship dissolution.
According to the National Survey of Sexual Health and Behavior (NSSHB), in 2010, men whose most recent sexual encounter was with a relationship partner reported greater arousal, greater pleasure, fewer problems with erectile function, orgasm, and less pain during the event than men whose last sexual encounter was with a non-relationship partner. According to the Journal of Counseling & Development, many women express that their most satisfying sexual experiences entail being connected to someone, rather than solely basing satisfaction on orgasm.
With regard to adolescent sexuality, sexual intercourse is often for relational and recreational purposes as well. However, teenage pregnancy is usually disparaged, and research suggests that the earlier onset of puberty for children puts pressure on children and teenagers to act like adults before they are emotionally or cognitively ready, and thus are at risk to suffer from emotional distress as a result of their sexual activities. Some studies have concluded that engaging in sex leaves adolescents, and especially girls, with higher levels of stress and depression. A majority of adolescents in the United States have been provided with some information regarding sexuality, though there have been efforts among social conservatives in the United States government to limit sex education in public schools to abstinence-only sex education curricula.
One group of Canadian researchers found a relationship between self-esteem and sexual activity. They found that students, especially girls, who were verbally abused by teachers or rejected by their peers were more likely than other students to engage in sex by the end of the Grade 7. The researchers speculate that low self-esteem increases the likelihood of sexual activity: "low self-esteem seemed to explain the link between peer rejection and early sex. Girls with a poor self-image may see sex as a way to become 'popular', according to the researchers".
In India, there is growing evidence that adolescents are becoming more sexually active outside of marriage, which is feared to lead to an increase in the spread of HIV/AIDS among adolescents, as well as the number of unwanted pregnancies and abortions, and add to the conflict between contemporary social values. In India, adolescents have relatively poor access to health care and education, and with cultural norms opposing extramarital sexual behavior, "these implications may acquire threatening dimensions for the society and the nation".
Not all views on adolescent sexual behavior are negative, however. Psychiatrist Lynn Ponton writes, "All adolescents have sex lives, whether they are sexually active with others, with themselves, or seemingly not at all," and that viewing adolescent sexuality as a potentially positive experience, rather than as something inherently dangerous, may help young people develop healthier patterns and make more positive choices regarding sexual activity. Similarly, others state that long-term romantic relationships allow adolescents to gain the skills necessary for high-quality relationships later in life and develop feelings of self-worth. Overall, positive romantic relationships among adolescents can result in long-term benefits. High-quality romantic relationships are associated with higher commitment in early adulthood and are positively associated with self-esteem, self-confidence, and social competence.
Ethical, religious, and legal views
While sexual intercourse is the natural mode of reproduction for the human species, humans have intricate moral and ethical guidelines which regulate the practice of sexual intercourse and vary according to religious and governmental laws. Some governments and religions also have strict designations of "appropriate" and "inappropriate" sexual behavior, which include restrictions on the types of sex acts which are permissible. A historically prohibited or regulated sex act is anal sex.
Consent and sexual offenses
Sexual intercourse with a person against their will, or without their informed legal consent, is rape, and is considered a serious crime in most countries. More than 90% of rape victims are female, 99% of rapists male, and only about 5% of rapists are strangers to the victims.
Most developed countries have age of consent laws specifying the minimum legal age a person may engage in sexual intercourse with substantially older persons, usually set at about 16–18, while the legal age of consent ranges from 12–20 years of age or is not a matter of law in other countries. Sex with a person under the age of consent, regardless of their stated consent, is often considered to be sexual assault or statutory rape depending on differences in ages of the participants. Some countries treat any sex with a person of diminished or insufficient mental capacity to give consent, regardless of age, as rape.
Scholars state "[p]rior to the 1970s, rape definitions of sex often included only penile-vaginal sexual intercourse" and that if "sex means penile-vaginal intercourse, then rape means forced penile-vaginal intercourse, and other sexual behaviors – such as fondling a person's genitals without her or his consent, forced oral sex, and same-sex coercion – are not considered rape"; they state that [a]lthough some other forms of forced sexual contact are included within the legal category of sodomy (e.g., anal penetration and oral-genital contact), many unwanted sexual contacts have no legal grounding as rape in some states".
The expression "sexual intercourse" has been used as a term of art in England and Wales and New York State. In England and Wales, from its enactment to its repeal on the 1 May 2004, section 44 of the Sexual Offences Act 1956 read:
Where, on the trial of any offence under this Act, it is necessary to prove sexual intercourse (whether natural or unnatural), it shall not be necessary to prove the completion of the intercourse by the emission of seed, but the intercourse shall be deemed complete upon proof of penetration only.
This expression refers to buggery, including both buggery with a person and buggery with an animal. Zoophilia (bestiality) is sexual activity between humans and non-human animals or a preference for or fixation on such practice. People who practice zoophilia are known as zoophiles, zoosexuals, or simply "zoos". Zoophilia may also be known as zoosexuality. Zoophilia is a paraphilia. Sex with animals is not outlawed in some jurisdictions, but, in most countries, it is illegal under animal abuse laws or laws dealing with crimes against nature.
According to cases decided on the meaning of the statutory definition of carnal knowledge under the Offences against the Person Act 1828, which was in identical terms to this definition, the slightest penetration was sufficient. The book "Archbold" said that it "submitted" that this continued to be the law under the new enactment.
For most definitions of rape, there is a broad "conceptualization of sex, including many kinds of sexual penetration (e.g., penile-vaginal intercourse, fellatio, cunnilingus, anal intercourse, or penetration of the genitals or rectum by an object)".
- Continuing act
See Kaitamaki v R  AC 147,  3 WLR 137,  2 All ER 435, 79 Cr App R 251,  Crim LR 564, PC (decided under equivalent legislation in New Zealand).
Section 7(2) of the Sexual Offences (Amendment) Act 1976 contained the following words: "In this Act . . . references to sexual intercourse shall be construed in accordance with section 44 of the Sexual Offences Act 1956 so far as it relates to natural intercourse (under which such intercourse is deemed complete on proof of penetration only)". The Act made provision, in relation to rape and related offences, for England and Wales, and for courts-martial elsewhere.
From 3 November 1994 to 1 May 2004, section 1(2)(a) of the Sexual Offences Act 1956 (as substituted by section 142 of the Criminal Justice and Public Order Act 1994) referred to "sexual intercourse with a person (whether vaginal or anal)". This section created the offence of rape in England and Wales.
The penal code in New York State provides: § 130.00 Sex offenses; definitions of terms: 1. "Sexual intercourse" has its ordinary meaning and occurs upon any penetration, however slight.
Sexual orientation and gender
There are various legal positions regarding the definition and legality of sexual intercourse between persons of the same sex or gender. For example, in the 2003 New Hampshire Supreme Court case Blanchflower v. Blanchflower, it was held that female same-sex sexual relations did not constitute sexual intercourse, based on a 1961 definition from Webster's Third New International Dictionary; and thereby an accused wife in a divorce case was found not guilty of adultery. Some countries, such as Islamic countries, consider homosexual behavior to be an offense punishable by imprisonment or execution.
Marriage and relationships
Sexual intercourse has traditionally been considered an essential part of a marriage; many religious customs required consummation of the marriage by sexual intercourse, and the failure for any reason to consummate the marriage was a ground for annulment, which did not require a divorce process. Annulment declaration implied that the marriage was void from the start – i.e. there was in law no marriage. Furthermore, continuing sexual relations between the marriage partners is commonly considered a 'marital right' by many religions, permissible to married couples, generally for the purpose of reproduction. Today, there is wide variation in the opinions and teachings about sexual intercourse relative to marriage and other intimate relationships by the world's religions. Examples:
- Most denominations of Christianity, including Catholicism, have strict views or rules on what sexual practices are acceptable or, more specifically, what are not. Most Christian views on sex are formed or influenced by various interpretations of the Bible. Sex outside of marriage is considered a sin in some churches, and sex may be referred to as a "sacred covenant" between husband and wife. Historically, Christian teachings often promoted celibacy, although today usually only certain members (for example certain religious leaders) of some groups take a vow of celibacy, forsaking both marriage and any type of sexual or romantic activity. Some Christians view sex, particularly sexual intercourse between a married couple, as "holy" or a "holy sacrament". Some Christians interpret the Bible to forbid the "misuse of sexual organs" and take that to mean that only penile-vaginal penetration is acceptable, while some argue that the Bible is not clear on oral sex and that it is a personal decision as to whether its acceptable within marriage.
- In The Church of Jesus Christ of Latter-day Saints, or Mormonism, sexual relations within the bonds of matrimony are seen as beautiful and sacred. Mormons consider sexual relations to be ordained of God for the creation of children and for the expression of love between husband and wife. Members are encouraged to not have any sexual relations before marriage, and be completely faithful to their spouse after marriage.
- In Judaism, a married Jewish man is required to provide his wife with sexual pleasure called onah (literally, "her time"), which is one of the conditions he takes upon himself as part of the Jewish marriage contract, ketubah, that he gives her during the Jewish wedding ceremony. In Jewish views on marriage, sexual desire is not evil, but must be satisfied in the proper time, place and manner.
- Islam views sex within marriage as something pleasurable, a spiritual activity, and a duty. In Shi'ia Islam, men are allowed to enter into an unlimited number of temporary marriages, which are contracted to last for a period of minutes to multiple years and permit sexual intercourse. Shi'ia women are allowed to enter only one marriage at a time, whether temporary or permanent.
- Wiccans believe that, as declared within the Charge of the Goddess, to "Let my [the Goddess] worship be within the heart that rejoiceth; for behold, all acts of love and pleasure are my rituals." This statement appears to allow one freedom to explore sensuality and pleasure, and mixed with the final maxim within the Wiccan Rede – "26. Eight words the Wiccan Rede fulfill – an’ it harm none, do what ye will." – Wiccans are encouraged to be responsible with their sexual encounters, in whatever variety they may occur.
- Hinduism has varied views about sexuality, but Hindu society, in general, perceives extramarital sex to be immoral and shameful.
- Buddhist ethics, in its most common formulation, holds that one should neither be attached to nor crave sensual pleasure.
- In the Bahá'í Faith, sexual relationships are permitted only between a husband and wife.
- Unitarian Universalists, with an emphasis on strong interpersonal ethics, do not place boundaries on the occurrence of sexual intercourse among consenting adults.
- According to the Brahma Kumaris and Prajapita Brahma Kumaris religion, the power of lust is the root of all evil and worse than murder. Purity (celibacy) is promoted for peace and to prepare for life in forthcoming Heaven on earth for 2,500 years when children will be created by the power of the mind.
- Shakers believe that sexual intercourse is the root of all sin and that all people should therefore be celibate, including married couples. Predictably, the original Shaker community that peaked at 6,000 full members in 1840 dwindled to three members by 2009.
In some cases, the sexual intercourse between two people is seen as counter to religious law or doctrine. In many religious communities, including the Catholic Church and Mahayana Buddhists, religious leaders are expected to refrain from sexual intercourse in order to devote their full attention, energy, and loyalty to their religious duties.
Opposition to same-sex marriage is largely based on the belief that sexual intercourse and sexual orientation should be of a heterosexual nature. The recognition of such marriages is a civil rights, political, social, moral, and religious issue in many nations, and the conflicts arise over whether same-sex couples should be allowed to enter into marriage, be required to use a different status (such as a civil union, which either grant equal rights as marriage or limited rights in comparison to marriage), or not have any such rights. A related issue is whether the term marriage should be applied.
With regard to zoology, copulation is often termed as the process in which a male introduces sperm into the female's body. Spiders have separate male and female sexes. Before mating and copulation, a male spins a small web and ejaculates on to it. He then stores the sperm in reservoirs on his large pedipalps, from which he transfers sperm to the female's genitals. Females can store sperm indefinitely.
Many animals which live in water use external fertilization, whereas internal fertilization may have developed from a need to maintain gametes in a liquid medium in the Late Ordovician epoch. Internal fertilization with many vertebrates (such as reptiles, some fish, and most birds) occur via cloacal copulation (see also hemipenis), while mammals copulate vaginally, and many basal vertebrates reproduce sexually with external fertilization.
However, some terrestrial arthropods do use external fertilization. For primitive insects, the male deposits spermatozoa on the substrate, sometimes stored within a special structure; courtship involves inducing the female to take up the sperm package into her genital opening, but there is no actual copulation. In groups such as dragonflies and spiders, males extrude sperm into secondary copulatory structures removed from their genital opening, which are then used to inseminate the female. In dragonflies, it is a set of modified sternites on the second abdominal segment; in spiders, it is the male pedipalps. In advanced groups of insects, the male uses its aedeagus, a structure formed from the terminal segments of the abdomen, to deposit sperm directly (though sometimes in a capsule called a "spermatophore") into the female's reproductive tract.
Humans, bonobos, chimpanzees and dolphins are species known to engage in heterosexual behaviors even when the female is not in estrus, which is a point in her reproductive cycle suitable for successful impregnation. These species, and others, are also known to engage in homosexual behaviors. Humans, bonobos and dolphins are all intelligent social animals, whose cooperative behavior proves far more successful than that of any individual alone. In these animals, the use of sexual intercourse has evolved beyond reproduction, to apparently serve additional social functions. Sexual activity reinforces intimate social bonds between individuals to form larger social structures. The resulting cooperation encourages collective tasks that promote the survival of each member of the group.
- Keath Roberts (2006). Sex. Lotus Press. p. 145. ISBN 8189093592,. Retrieved August 17, 2012.
- Wayne Weiten, Margaret A. Lloyd, Dana S. Dunn, Elizabeth Yost Hammer (2008). Psychology Applied to Modern Life: Adjustment in the 21st Century. Cengage Learning. p. 423. ISBN 0495553395,. Retrieved January 5, 2012.
- Cecie Starr, Beverly McMillan (2008). Human Biology. Cengage Learning. p. 314. ISBN 0495561819,. Retrieved April 30, 2013.
- "Sexual intercourse". Collins English Dictionary. Retrieved September 5, 2012.
- Kar (2005). Comprehensive Textbook of Sexual Medicine. Jaypee Brothers Publishers. pp. 107–112. ISBN 8180614050,. Retrieved September 4, 2012.
- "Sexual Intercourse". health.discovery.com. Archived from the original on 2008-08-22. Retrieved 2008-01-12.
- The Gender of Sexuality: Exploring Sexual Possibilities; Page 76 – Virginia Rutter, Pepper Schwartz – 2011
- Diamond, Jared (1992). The rise and fall of the third chimpanzee. Vintage. ISBN 978-0-09-991380-1.
- Richard M. Lerner, Laurence Steinberg (2004). Handbook of Adolescent Psychology. John Wiley & Sons. pp. 193–196. ISBN 0471690449. Retrieved April 29, 2013. "When researchers use the term sex, they nearly always mean sexual intercourse – more specifically, penile-vaginal intercourse... The widespread, unquestioned equation of penile-vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question matches what the researcher had in mind.'"
- Randall, H. E., & Byers, S. E. (2003). "What is sex? Students' definitions of having sex, sexual partner, and unfaithful sexual behaviour". The Canadian Journal of Human Sexuality 12: 87–96. "Recently, researchers in the United States, the United Kingdom, and Australia have investigated university students' definitions of having sex. These studies found that students differ in their opinions of what sexual behaviours constitute having sex (Pitts & Rahman, 2001; Richters & Song, 1999; Sanders & Reinisch, 1999). While the vast majority of respondents (more than 97%) in these three studies included penile-vaginal intercourse in their definition of sex, fewer (between 70% and 90%) respondents considered penile-anal intercourse to constitute having sex. Oral-genital behaviours were defined as sex by between 32% and 58% of respondents."
- See here and pages 47-49 for views on what constitutes virginity loss and therefore sexual activity; source discusses how gay and lesbian individuals define virginity loss, and how the majority of researchers and heterosexuals define virginity loss/"technical virginity" by whether or not a person has engaged in vaginal sex. Laura M. Carpenter (2005). Virginity lost: an intimate portrait of first sexual experiences. NYU Press. pp. 295 pages. ISBN 0-8147-1652-0,. Retrieved October 9, 2011. "Many studies, moreover, seemed uncritically to lump nonvirgin teens (so designated if they'd had vaginal sex) together with their alcohol–and drug–using peers 'at risk' for negative outcomes from unintended pregnancy and STIs (sexually transmitted infections) to academic failure and low self-esteem."
- Paula Kamen (2000). Her Way: Young Women Remake the Sexual Revolution. New York University Press. pp. 74–77. ISBN 0814747337,. Retrieved September 5, 2012.
- Jerry D. Durham, Felissa R. Lashley (2000). The Person With HIV/AIDS: Nursing Perspectives, 3rd Edition. Springer Publishing Company. p. 103. ISBN 8122300049,. Retrieved January 29, 2012.
- "Defining sexual health: Report of a technical consultation on sexual health". World Health Organization. January 2002. p. 4. Retrieved September 5, 2012. "In English, the term 'sex' is often used to mean 'sexual activity' and can cover a range of behaviours. Other languages and cultures use different terms, with slightly different meanings."
- Klein, Marty. "The Meaning of Sex". Electronic Journal of Human Sexuality, Volume 1 August 10, 1998:. Retrieved 2007-12-09.
- "Global strategy for the prevention and control of sexually transmitted infections: 2006–2015. Breaking the chain of transmission". World Health Organization. 2007. Retrieved November 26, 2011.
- "Sexually Transmitted Disease Surveillance". Centers for Disease Control and Prevention (CDC). 2008. Retrieved December 6, 2011. Also see Fact Sheet
- "Sexual Risk Factors". AIDS.gov. Retrieved March 4, 2011.
- Carpenter, Laura M. (2001). "The Ambiguity of "Having Sex": The Subjective Experience of Virginity Loss in the United States - Statistical Data Included". United States: The Journal of Sex Research. Retrieved September 5, 2012.
- Bryan Strong, Christine DeVault, Theodore F. Cohen (2010). The Marriage and Family Experience: Intimate Relationship in a Changing Society. Cengage Learning. p. 186. ISBN 0-534-62425-1,. Retrieved October 8, 2011. "Most people agree that we maintain virginity as long as we refrain from sexual (vaginal) intercourse. ... Other research, especially research looking into virginity loss, reports that 35% of virgins, defined as people who have never engaged in vaginal intercourse, have nontheless engaged in one or more other forms of heterosexual activity (e.g. oral sex, anal sex, or mutual masturbation). ... Data indicate that 'a very significant proportion of teens ha[ve] had experience with oral sex, even if they haven't had sexual intercourse, and may think of themselves as virgins'."
- Bersamin MM, Walker S, Waiters ED, Fisher DA, Grube JW (May 2005). "Promising to wait: virginity pledges and adolescent sexual behavior". J Adolesc Health 36 (5): 428–36. doi:10.1016/j.jadohealth.2004.09.016. PMC 1949026. PMID 15837347.
- Daniel L. Akin. God on Sex: The Creator's Ideas About Love, Intimacy, and Marriage. (2003). B&H Publishing Group. ISBN 0-8054-2596-9
- Michael Kent (2000). Advanced biology. Oxford University Press. pp. 250–253. ISBN 0199141959,.
- Showick Thorpe, Edgar Thorpe (2009). The Pearson General Studies Manual 2009, 1/e. Pearson Education India. p. page 17 (xvii). ISBN 8131721337,.
- Frans de Waal, "Bonobo Sex and Society", Scientific American (March 1995) 82–86.
- Bailey NW, Zuk M (August 2009). "Same-sex sexual behavior and evolution". Trends Ecol. Evol. (Amst.) 24 (8): 439–46. doi:10.1016/j.tree.2009.03.014. PMID 19539396.
- Bruce Bagemihl, Biological Exuberance: Animal Homosexuality and Natural Diversity (St. Martin's Press, 1999). ISBN 0-312-19239-8
- Balcombe, J. Pleasurable Kingdom: Animals and the Nature of Feeling Good. Macmillan, New York, 2007. 360 pp. ISBN 1-4039-8602-9 
- Ada P. Kahn, Jan Fawcett (2008). The Encyclopedia of Mental Health. Infobase Publishing. p. 111. ISBN 0816064547,. Retrieved September 5, 2012.
- "Coitus". Merriam-Webster. Retrieved September 6, 2012.
- "Coitus". Random House Webster's Unabridged Dictionary. 2013. Retrieved September 6, 2012.
- "Intromission". Merriam-Webster. Retrieved December 26, 2012.
- "Copulation". Dorland's Medical Dictionary for Health Consumers. 2007. Retrieved September 6, 2012.
- "Copulation". The American Heritage Dictionary of the English Language. 2000/2009.
- Cox, Lauren (March 8, 2010). "Study: Adults Can't Agree What 'Sex' Means". ABC.com. Retrieved September 5, 2012.
- "Fuck". Merriam-Webster. Retrieved March 30, 2013.
- "Sleep together". thefreedictionary.com. Retrieved March 30, 2013.
- Andrew Baum, Tracey A. A. Revenson, Jerome Singer (2012). Handbook of Health Psychology, 2nd Edition. Psychology Press. pp. 259–260. ISBN 080586461X,. Retrieved April 30, 2013.
- Richard D. McAnulty, M. Michele Burnette (2003). Exploring Human Sexuality: Making Healthy Decisions. Allyn & Bacon. p. 229. ISBN 020538059X,. 9780763741488,.
- Arthur G. Miller (1999). Perspectives on Evil and Violence. Psychology Press. p. 240. ISBN 0805897844,. Retrieved April 29, 2013. "Many people consider penile-vaginal intercourse the only form of 'real' sex."
- Pamela J. Kalbfleisch, Michael J. Cody (2012). Gender Power and Communication in Human Relationships. Routledge. ISBN 1136480501,. Retrieved April 30, 2013.
- Robert Crooks, Karla Baur (2010). Our Sexuality. Cengage Learning. pp. 286–289. ISBN 0495812943,. Retrieved August 30, 2012. "Noncoital forms of sexual intimacy, which have been called outercourse, can be a viable form of birth control. Outercourse includes all avenues of sexual intimacy other than penile–vaginal intercourse, including kissing, touching, mutual masturbation, and oral and anal sex."
- Mark Regnerus (2007). "The Technical Virginity Debate: Is Oral Sex Really Sex?". Forbidden Fruit: Sex & Religion in the Lives of American Teenagers. Oxford University Press US. pp. 290 pages. ISBN 978-0-19-532094-7.
- Joseph Gross, Michael (2003). Like a Virgin. The Advocate/Here Publishing. p. 44. 0001-8996. Retrieved 2011-03-13.
- Steven Gregory Underwood (2003). Gay men and anal eroticism: tops, bottoms, and versatiles. Psychology Press. p. 4. ISBN 978-1-56023-375-6. 1560233753, 9781560233756. Retrieved 2011-02-12.
- Joe Perez (2006). Rising Up. Lulu.com. pp. 190–192. ISBN 1-4116-9173-3,. Retrieved March 24, 2011.
- Dolby, Tom (February 2004). "Why Some Gay Men Don't Go All The Way". Out. pp. 76–77. Retrieved 2011-02-12.
- Blank, Hanne (2008). Virgin: The Untouched History. Bloomsbury Publishing USA. p. 253. ISBN 1-59691-011-9,. Retrieved October 8, 2011.
- Karen Bouris (1995). The first time: what parents and teenage girls should know about "losing your virginity". Conari Press. pp. 133–134. ISBN 0-943233-93-3,.
- Jerrold S. Greenberg, Clint E. Bruess, Sarah C. Conklin (2007). Exploring the Dimensions of Human Sexuality. Jones & Bartlett Learning. p. 429. ISBN 0-7637-4148-5,. 9780763741488. Retrieved 2010-12-19.
- Michael R Kauth (2000). True Nature: A Theory of Sexual Attraction. Springer. p. 74. ISBN 0306463903,. Retrieved August 30, 2012.
- Jayson, Sharon (2005-10-19). "'Technical virginity' becomes part of teens' equation". USA Today. Retrieved 2009-08-07.
- Wayne Weiten, Dana S. Dunn, Elizabeth Yost Hammer (2011). Psychology Applied to Modern Life: Adjustment in the 21st Century. Cengage Learning. pp. 384–386. ISBN 1-111-18663-4,. Retrieved January 5, 2012.
- "'I Want a Better Orgasm!'". WebMD. Retrieved August 18, 2011.
- Joseph A. Flaherty, John Marcell Davis, Philip G. Janicak (1993, Digitized Oct 29, 2010). Psychiatry: Diagnosis & therapy. A Lange clinical manual. Appleton & Lange (Original from Northwestern University). pp. 544 pages. ISBN 0-8385-1267-4,. "The amount of time of sexual arousal needed to reach orgasm is variable — and usually much longer — in women than in men; thus, only 20–30% of women attain a coital climax. b. Many women (70–80%) require manual clitoral stimulation..."
- Mah, Kenneth; Binik, Yitzchak M (2001, available online on July 17, 2001). "The nature of human orgasm: a critical review of major trends". Clinical Psychology Review 21 (6): 823–856. doi:10.1016/S0272-7358(00)00069-6. PMID 11497209. "Women rated clitoral stimulation as at least somewhat more important than vaginal stimulation in achieving orgasm; only about 20% indicated that they did not require additional clitoral stimulation during intercourse."
- Kammerer-Doak, Dorothy; Rogers, Rebecca G. (2008, available online on May 16, 2008). "Female Sexual Function and Dysfunction". Obstetrics and Gynecology Clinics of North America 35 (2): 169–183. doi:10.1016/j.ogc.2008.03.006. PMID 18486835. "Most women report the inability to achieve orgasm with vaginal intercourse and require direct clitoral stimulation ... About 20% have coital climaxes..."
- Elisabeth Anne Lloyd (2005). The case of the female orgasm: bias in the science of evolution. Harvard University Press. pp. 311 pages. ISBN 0-674-01706-4,. Retrieved January 5, 2012.
- O'Connell HE, Sanjeevan KV, Hutson JM (October 2005). "Anatomy of the clitoris". The Journal of Urology 174 (4 Pt 1): 1189–95. doi:10.1097/01.ju.0000173639.38898.cd. PMID 16145367. Lay summary – BBC News (11 June 2006).
- Hurlbert DF, Apt C (1995). "The coital alignment technique and directed masturbation: a comparative study on female orgasm". Journal of Sex & Marital Therapy. 21(1) (1): 21–29. doi:10.1080/00926239508405968. PMID 7608994.
- Dr. John Dean and Dr. David Delvin. "Anal sex". Netdoctor.co.uk. Retrieved April 29, 2010.
- Barry R. Komisaruk, Beverly Whipple, Sara Nasserzadeh, Carlos Beyer-Flores (2009). The Orgasm Answer Guide. JHU Press. pp. 108–109. ISBN 0-8018-9396-8,. Retrieved November 6, 2011.
- Hite, Shere (2003). The Hite Report: A Nationwide Study of Female Sexuality. New York, NY: Seven Stories Press. pp. 512 pages. ISBN 1-58322-569-2,. Retrieved March 2, 2012.
- Carroll, Janell L. (2009). Sexuality Now: Embracing Diversity. Cengage Learning. pp. 118, 252, and 264. ISBN 978-0-495-60274-3. Retrieved 23 June 2012. "...In fact, most women do not enjoy direct stimulation of the [clitoral] glans and prefer stimulation through the [hood]... The majority of women enjoy a light caressing of the shaft of the clitoris, together with an occasional circling of the [clitoral glans], and maybe digital (finger) penetration of the vagina. Other women dislike direct stimulation and prefer to have the [clitoral glans] rolled between the lips of the labia. Some women like to have the entire area of the vulva caressed, whereas others like the caressing to be focused on the [clitoral glans]. Women report that clitoral stimulation feels best when the fingers are well lubricated."
- "Premature ejaculation". Mayo Clinic.com. Retrieved 2007-03-02.
- "Anorgasmia in women". Mayo Clinic.com. Retrieved 2010-11-23.
- June M. Reinisch, Ruth Beasley (1991). The Kinsey Institute New Report On Sex. Macmillan. pp. 129–130. ISBN 0312063865,. Retrieved August 30, 2012.
- "Corty, E., & Guardiani, J. (2008) Canadian and American Sex Therapists' Perceptions of Normal and Abnormal Ejaculatory Latencies: How Long Should Intercourse Last?.". The Journal of Sexual Medicine 5(5). interscience.wiley.com. 2008-03-04. pp. 1251–1256. doi:10.1111/j.1743-6109.2008.00797.x. Retrieved 2010-11-23.
- "Sex therapists: Best sex is 7 to 13 min". Upi.com. March. 5, 2008. Retrieved September 5, 2012.
- Frank JE, Mistretta P, Will J (March 2008). "Diagnosis and treatment of female sexual dysfunction". American family physician 77 (5): 635–42. PMID 18350761.
- Laumann, E., Gagnon, J.H., Michael, R.T., and Michaels (1994). "The Social Organization of Sexuality: Sexual Practices in the United States". University of Chicago Press (Also reported in the companion volume, Michael et al, Sex in America: A Definitive Survey.). Retrieved January 3, 2012.
- Reissing ED, Binik YM, Khalifé S, Cohen D, Amsel R (2003). "Etiological correlates of vaginismus: sexual and physical abuse, sexual knowledge, sexual self-schema, and relationship adjustment". J Sex Marital Ther. 29 (1): 47–59. doi:10.1080/713847095. PMID 12519667.
- Ward E, Ogden J (1994). "Experiencing Vaginismus: sufferers beliefs about causes and effects". The Journal of Nervous and Mental Disease 9 (1): 33–45.
- Shafik A., El-Sibai O. (2000). "Vaginismus: Results of treatment with botulin toxin". Journal of Obstetrics & Gynaecology 20 (3): 300–302. doi:10.1080/01443610050009674.
- Binik YM (February 2005). "Should dyspareunia be retained as a sexual dysfunction in DSM-V? A painful classification decision". Arch Sex Behav 34 (1): 11–21. doi:10.1007/s10508-005-0998-4. PMID 15772767.
- Peckham BM, Maki DG, Patterson JJ, Hafez GR (April 1986). "Focal vulvitis: a characteristic syndrome and cause of dyspareunia. Features, natural history, and management". Am J Obstet Gynecol. 154 (4): 855–64. PMID 3963075.
- Schouten BW, Bohnen AM, Groeneveld FP, Dohle GR, Thomas S, Bosch JL (July 2010). "Erectile dysfunction in the community: trends over time in incidence, prevalence, GP consultation and medication use—the Krimpen study: trends in ED". J Sex Med 7 (7): 2547–53. doi:10.1111/j.1743-6109.2010.01849.x. PMID 20497307.
- Heidelbaugh JJ (February 2010). "Management of erectile dysfunction". Am Fam Physician 81 (3): 305–12. PMID 20112889.
- Erectile Dysfunction Guideline Update Panel. AUA guideline on the pharmacologic management of premature ejaculation. Linthicum (MD): American Urological Association, Inc.; 2004. 19 p.
- Riley, A; Segraves, RT; R.T. Segraves (2006). "Treatment of Premature Ejaculation". Int J. Clin Pract. (Blackwell Publishing) 60 (6): 694–697. doi:10.1111/j.1368-5031.2006.00818.x. PMID 16805755. Retrieved 2008-02-01.
- Hengeveld VW et al., Waldinger MD; Hengeveld, MW; Zwinderman, AH; Olivier, B (1998). "Effect of SSRI antidepressants on ejaculation: a double blind, randomised, placebo-controlled study with fluoxetine, fluvoxamine, paroxetine and sertraline". Journal of Clinical Psychopharmacology 18 (4): 274–281. doi:10.1097/00004714-199808000-00004. PMID 9690692.
- Williamson, Gail M.; Walters, Andrew S. (1996). "Perceived Impact of Limb Amputation on Sexual Activity: A Study of Adult Amputees". The Journal of Sex Research (Taylor & Francis Group (Lawrence Erlbaum Associates)) 33 (3): 221–230. doi:10.1080/00224499609551838. ISSN 0022-4499. JSTOR 3813582. OCLC 39109327.
- Majiet, Shanaaz (1993). "Disabled Women and Sexuality". Agenda (Agenda Feminist Media) (19): 43–44. doi:10.2307/4065995. JSTOR 4065995.
- Dewolfe, Deborah J.; Livingston, Carolyn A. (August 1, 1982). "Sexual Therapy for a Woman with Cerebral Palsy: A Case Analysis". The Journal of Sex Research (Taylor & Francis Group (Lawrence Erlbaum Associates)) 18 (3): 253–263. doi:10.1080/00224498209551151. ISSN 0022-4499. JSTOR 3812217. OCLC 39109327.
- Crowe LC, George WH (May 1989). "Alcohol and human sexuality: review and integration". Psychol Bull 105 (3): 374–86. doi:10.1037/0033-2909.105.3.374. PMID 2660179.
- Alcohol Use and Sexual Risk Behaviour: A Cross-cultural Study in Eight Countries. World Health Organization. 2005. pp. 135 pages. ISBN 9241562897,. Retrieved March 30, 2013.
- Richard Evan Jones, Kristin H. López (2006). Human Reproductive Biology. Academic Press. pp. 604 pages. ISBN 0120884658,. Retrieved November 8, 2012.
- Jared Diamond (1997). Why Is Sex Fun?. Basic Books. ISBN 0-465-03127-7.
- Ozolins, John. "Surrogacy: Exploitation or Violation of Intimacy?". Boston University. Retrieved 13 July 2010. "This concern for the unity of the spouses seems to be why artificial insemination of a surrogate in cases where the wife cannot supply a fertile ovum is preferred, rather than natural insemination, since it does not involve any relationship with the surrogate"
- "Not Every Pregnancy is Welcome". The world health report 2005 – make every mother and child count. World Health Organization. Retrieved 6 December 2011.
- "Get "In the Know": 20 Questions About Pregnancy, Contraception and Abortion". Guttmacher Institute. 2005. Retrieved March 4, 2011.
- Ventura, SJ, Abma, JC, Mosher, WD, & Henshaw, S. (2007-11-16). "Estimated pregnancy rates for the United States, 1990–2000: An Update. National Vital Statistics Reports, 52 (23)". cdc.gov. Retrieved March 4, 2011.
- Christine Webber, psychotherapist and Dr David Delvin. "Talking to pre-adolescent children about sex". Broaching the subject. Net Doctor. Retrieved August 5, 2011.
- Berkowitz D, Marsiglio W (2007). "Gay Men: Negotiating Procreative, Father, and Family Identities". Journal of Marriage and Family 69 (2): 366–381. doi:10.1111/j.1741-3737.2007.00371.x.
- Joan M. Burda (2008). Gay, lesbian, and transgender clients: a lawyer's guide. American Bar Association. pp. 69–74. ISBN 1-59031-944-3,. Retrieved July 28, 2011.
- Tagami T, Matsubara Y, Hanada H, Naito M. (June 1997). "Differentiation of female chicken primordial germ cells into spermatozoa in male gonads". Dev. Growth Differ. 39 (3): 267–71. doi:10.1046/j.1440-169X.1997.t01-2-00002.x. PMID 9227893.
- "Japanese scientists produce mice without using sperm". Washington Post (Sarasota Herald-Tribune). April 22, 2004. Retrieved July 28, 2011.
- Elizabeth Bernstein, Laurie Schaffner (2005). Regulating sex: the politics of intimacy and identity. Perspectives on gender. Psychology Press. p. 22. ISBN 0-415-94869-X,. Retrieved July 28, 2011.
- Feldmann, J.; Middleman, A. B. (2002). "Adolescent sexuality and sexual behavior". Current opinion in obstetrics & gynecology 14 (5): 489–493. PMID 12401976.
- "STI Epi Update: Oral Contraceptive and Condom Use". Public Health Agency of Canada. 1998-04-23. Retrieved 2007-07-11.
- National Institute of Allergy and Infectious Diseases; National Institutes of Health, Department of Health and Human Services (2001-07-20). "Workshop Summary: Scientific Evidence on Condom Effectiveness for Sexually Transmitted Disease (STD) Prevention" (PDF). Hyatt Dulles Airport, Herndon, Virginia. pp. 13–15. Archived from the original on 2010-03-15. Retrieved 2009-03-20.
- World Health Organization. Effectiveness of male latex condoms in protecting against pregnancy and sexually transmitted infections , 2000.
- Dianne Hales (2010). An Invitation to Health: Choosing to Change. Cengage Learning. pp. 301–302. ISBN 0538736550,. Retrieved March 30, 2013.
- Winner B, Peipert JF, Zhao Q, et al. (May 2012), "Effectiveness of long-acting reversible contraception", N. Engl. J. Med. 366 (21): 1998–2007, doi:10.1056/NEJMoa1110855, PMID 22621627
- "Contraceptive Use". Guttmacher Institute. 2010. Retrieved March 4, 2011.
- "Sexual Health Statistics for Teenagers and Young Adults in the United States" (PDF). Kaiser Family Foundation. September 2006. Retrieved 2008-07-02.
- "Findings from the National Survey of Sexual Health and Behavior, Centre for Sexual Health Promotion, Indiana University". The Journal of Sexual Medicine. 7, Supplement 5.: 4 2010. Retrieved March 4, 2011.
- Bozon, Michael (2003). "At what age do women and men have their first sexual intercourse? World comparisons and recent trends". Population and Societies 391: 1–4.
- "Sexual and Reproductive Health: Women and Men". Guttmacher Institute. 2002. Archived from the original on July 26, 2011. Retrieved December 26, 2012.
- "Seventeen Is the Average Age at First Sexual Intercourse" (pdf). American Sexual Behavior. newstrategist.com. Archived from the original on January 24, 2013. Retrieved March 23, 2013.
- "Fertility, Family Planning, and Reproductive Health of U.S.Women: Data From the 2002 National Survey of Family Growth". Centers for Disease Control and Prevention (CDC). Retrieved 9 February 2013.
- "Fertility, Contraception, and Fatherhood: Data on Men and Women From Cycle 6 (2002) of the National Survey of Family Growth". Centers for Disease Control and Prevention (CDC). Retrieved 9 February 2013.
- "Key Statistics from the National Survey of Family Growth". Centers for Disease Control and Prevention (CDC). Retrieved 9 February 2013.
- "Teenagers in the United States: Sexual Activity, Contraceptive Use, and Childbearing, 2006–2010 National Survey of Family Growth" (pdf). Centers for Disease Control and Prevention (CDC). Retrieved December 26, 2012.
- "Teenagers in the United States: Sexual Activity, Contraceptive Use, and Childbearing, 2002". Centers for Disease Control and Prevention (CDC). Retrieved 9 February 2013.
- Denis Campbell (January 22, 2006). "No sex please until we're at least 17 years old, we're British". The Observer. Retrieved March 14, 2013.
- "Teen Sex Survey". Channel 4. 2008. Retrieved August 5, 2011.
- Wood, H. Sex Cells Nature Reviews Neuroscience 4, 88 (February 2003) | doi:10.1038/nrn1044
- Doheny, K. (2008) "10 Surprising Health Benefits of Sex," WebMD (reviewed by Chang, L., M.D.)
- Light, K.C. et al., "More frequent partner hugs and higher oxytocin levels are linked to lower blood pressure and heart rate in premenopausal women." Biological Psychology, April 2005; vol 69: pp 5–21.
- Charnetski CJ, Brennan FX (2004). "Sexual frequency and salivary immunoglobulin A (IgA)". Psychological Reports 94 (3): 839–44. doi:10.2466/pr0.94.3.839-844. PMID 15217036. "Data on length of relationship and sexual satisfaction were not related to the group differences"
- Michael F. Leitzmann; Edward Giovannucci. "Frequency of Ejaculation and Risk of Prostate Cancer—Reply. JAMA. (2004);292:329.
- Leitzmann MF, Platz EA, Stampfer MJ, Willett WC, Giovannucci E (2004). "Ejaculation Frequency and Subsequent Risk of Prostate Cancer". JAMA 291 (13): 1578–1586. doi:10.1001/jama.291.13.1578. PMID 15069045.
- Giles GG, Severi G, English DR, et al. (August 2003). "Sexual factors and prostate cancer". BJU Int. 92 (3): 211–6. doi:10.1046/j.1464-410X.2003.04319.x. PMID 12887469.
- Lee HJ, Macbeth AH, Pagani JH, Young WS (June 2009). "Oxytocin: the great facilitator of life". Prog. Neurobiol. 88 (2): 127–51. doi:10.1016/j.pneurobio.2009.04.001. PMC 2689929. PMID 19482229.
- Riley AJ. Oxytocin and coitus. Sexual and Relationship Therapy (1988);3:29–36
- Carter CS. "Oxytocin and sexual behavior. Neuroscience & Biobehavioral Reviews 1992;16(2) 131–144
- Thayer, R. E., Newman, J., & McClain, T. M. (1994). Self-regulation of mood: Strategies for changing a bad mood, raising energy, and reducing tension. Journal Of Personality And Social Psychology, 67(5), 910–925.
- Blum, Jeffrey. "Can Good Sex Keep You Young?". WebMD. Retrieved 8 October 2010.
- Weeks, David (1999). Secrets of the Superyoung. Berkley. p. 277. ISBN 978-0-425-17258-2.
- Northrup, Christiane (2010). Women's Bodies, Women's Wisdom: Creating Physical and Emotional Health and Healing. Bantam. p. 960. ISBN 978-0-553-80793-6.
- "STD Trends in the United States: 2010 National Data for Gonorrhea, Chlamydia, and Syphilis". Centers for Disease Control and Prevention. Retrieved 15 September 2012.
- "Sexually transmitted infections". Fact sheet N° 110. World Health Organization. August 2011. Retrieved 8 September 2012.
- Thompson, Jonathan (November 12, 2006). "New safe sex ads target teens 'on the pull'". The Independent. Retrieved March 27, 2013.
- CDC Hepatitis B Information for Health Professionals Accessed May 27, 2010
- "Hepatitis B". World Health Organization. Retrieved 15 September 2012.
- "HIV/AIDS". World Health Organization. Retrieved 15 September 2012.
- "HIV/AIDS". Fact sheet N° 360. World Health Organization. July 2012. Retrieved 8 September 2012.
- Derogaatis, L.R.; Derogatis LR, King KM (August 1981). "The coital coronary: A reassessment of the concept". Arch Sex Behav 10 (4): 325–335. PMID 7295015.
- Dahabreh, Issa J. (23 March 2011). "Association of Episodic Physical and Sexual Activity With Triggering of Acute Cardiac Events. Systematic Review and Meta-analysis.". JAMA: The Journal of the American Medical Association 305 (12): 1225. doi:10.1001/jama.2011.336. "Acute cardiac events were significantly associated with episodic physical and sexual activity; this association was attenuated among persons with high levels of habitual physical activity."
- The Joy of Sex: A Gourmet Guide to Lovemaking (1972)
- Bramlett, M. D. and W. D. Mosher (2002). "Cohabitation, marriage, divorce, and remarriage in the United States." Vital & Health Statistics – Series 23, Data from the National Survey of Family Growth 22: 1–93.
- Karney B. R., Bradbury T. N. (1995). "The longitudinal course of marital quality and stability: A review of theory, methods, and research". Psychological Bulletin 118 (1): 3–34. doi:10.1037/0033-2909.118.1.3. PMID 7644604.
- "Predicting sexual satisfaction in women: Implications for counselor education and training". Journal of Counseling & Development. 82(2): 158–166. 2004. Retrieved March 4, 2011.
- Ponton, Lynn (2000). The Sex Lives of Teenagers. New York: Dutton. p. 3. ISBN 978-0-452-28260-5.
- Garn, SM. Physical growth and development. In: Friedman SB, Fisher M, Schonberg SK. , editors. Comprehensive Adolescent Health Care. St Louis: Quality Medical Publishing; 1992. Retrieved on 2009-02-20
- Jayson, Sharon (2005-10-19). "Teens define sex in new ways". USA Today. Retrieved 2007-12-08.
- Mark O'Connell (March 9, 2005). "The epidemic of meaningless teen sex". The Boston Globe. Retrieved 2008-04-09.
- (Caspi et al.1993: Lanza and Collins, 2002)
- (Stattin & Magnussion, 1990).
- Denise D. Hallfors PhD, Martha W. Waller PhD, Daniel Bauer PhD, Carol A. Ford MD, and Carolyn T. Halpern PhD (2005). "Which Comes First in Adolescence—Sex and Drugs or Depression?" (PDF). American Journal of Preventive Medicine 29 (3): 163–170. doi:10.1016/j.amepre.2005.06.002. PMID 16168864.
- Katie Couric (2005). "Nearly 3 in 10 young teens 'sexually active'". MSNBC. Retrieved 2007-01-21.
- "Sex Education in the U.S.: Policy and Politics" (PDF). Issue Update. Kaiser Family Foundation. October 2002. Retrieved 2010-12-14.
- "Peer rejection tied to early sex in pre-teens" (PDF). Issue Update. MedlinePlus. October 2002. Archived from the original on 2007-10-11. Retrieved August 5, 2011.
- R.S.Goya, Indian Institute of Health Management Research, Jaipur, India (2005). "Socio-psychological Constructs of Premarital Sex Behavior among Adolescent Girls in India" (PDF). Abstract. Princeton University. Retrieved August 5, 2011.
- Madsen S., Collins W. A. (2005). Differential predictions of young adult romantic relationships from transitory vs. longer romantic experiences during adolescence. Presented at Biennial Meeting of the Society for Research on Child Development, Atlanta, GA.
- Seiffge-Krenke I., Lang J. (2002). Forming and maintaining romantic relations from early adolescence to young adulthood: evidence of a developmental sequence. Presented at Biennial Meeting of the Society for Research on Adolescence, 19th, New Orleans, LA.
- Pearce M. J., Boergers J., Prinstein M.J. (2002). "Adolescent obesity, overt and relational peer victimization, and romantic relationships". Obesity Research 10 (5): 386–93. doi:10.1038/oby.2002.53. PMID 12006638.
- Zimmer-Gembeck M.J., Siebenbruner J., Collins W.A. (2004). "A prospective study of intraindividual and peer influences on adolescents' heterosexual romantic and sexual behavior". Archives of Sexual Behavior 33 (4): 381–394. doi:10.1023/B:ASEB.0000028891.16654.2c. PMID 15162084.
- William N. Eskridge Jr. Dishonorable Passions: Sodomy Laws in America, 1861–2003. (2008) Viking Adult. ISBN 0-670-01862-7
- Noelle N. R. Quenivet. Sexual Offenses in Armed Conflict & International Law. (2005) Hotei Publishing. ISBN 1-57105-341-7
- Marshall Cavendish Corporation Staff. Sex and Society. (2009) Cavendish, Marshall Corporation. p143-144. ISBN 0-7614-7906-6 
- Jerrold S. Greenberg, Clint E. Bruess, Sarah C. Conklin. (2010). Exploring the Dimensions of Human Sexuality. p 515. ISBN 0-7637-7660-2 .
- Karen L. Kinnear. (2007) Childhood sexual abuse: a reference handbook. ABC-CLIO. ISBN 1-85109-905-0 
- Reed, E. J. (1997). "Criminal Law and the Capacity of Mentally Retarded Persons to Consent to Sexual Activity". Virginia Law Review 83 (4): 799–827. doi:10.2307/1073749. JSTOR 1073749.
- Robert T. Francoeur, Raymond J. Noonan, Beldina Opiyo-Omolo (2004). The Continuum Complete International Encyclopedia of Sexuality. Continuum International Publishing Group. p. 173. ISBN 0826414885,. Retrieved April 30, 2013.
- The Sexual Offences Act 2003 (Commencement) Order 2004 (S.I. 2004/874)
- R v Gaston 73 Cr App R 164, CA
- "Zoophilia," Encyclopaedia Britannica, 2009; Retrieved 24 January 2009.
- Ascione, Frank (28 February 2010). The International Handbook of Animal Abuse and Cruelty: Theory, Research, and Application. ISBN 978-1-55753-565-8.
- Diagnostic and Statistical Manual of Mental Disorders: DSM-IV. Washington, DC: American Psychiatric Association. 2000. ISBN 0-89042-025-4.
- Milner, JS; Dopke CA (2008). "Paraphilia Not Otherwise Specified: Psychopathology and theory". In Laws DR & O'Donohue WT. Sexual Deviance, Second Edition: Theory, Assessment, and Treatment. New York: The Guilford Press. pp. 384–418. ISBN 1-59385-605-9.
- Money, John (1988). Lovemaps: Clinical Concepts of Sexual/Erotic Health and Pathology, Paraphilia, and Gender Transposition in Childhood, Adolescence, and Maturity. Buffalo, N.Y: Prometheus Books. ISBN 0-87975-456-7.
- Seto, MC; Barbaree HE (2000). "Paraphilias". In Hersen M; Van Hasselt VB. Aggression and violence: an introductory text. Boston: Allyn & Bacon. pp. 198–213. ISBN 0-205-26721-1.
- R v R'Rue (1838) 8 C & P 641; R v Allen (1839) 9 C & P 31
- Archbold Criminal Pleading, Evidence and Practice, 1999, paragraph 20–24
- "Laws of New York, leginfo.state.ny". Public.leginfo.state.ny.us. Retrieved 2011-07-30.
- Janet Afary. Sexual Politics in Modern Iran. (2009) Cambridge University Press. ISBN 0-521-89846-3
- Smith, Janet E. "The Christian View of Sex: A Time for Apologetics, Not Apologies – by Janet E Smith, University of Dallas". Natural Family Planning Outreach. Retrieved 8 December 2011.
- Gordon, Jim and Carrie. "Christian Views on Sex". The Intimate Couple. Retrieved 8 December 2011.
- "Christianity and Sex". Books and Articles: Scholarly Publications on The Family. The Family International (in Family Dossier). Retrieved 8 December 2011.
- Taylor, Ross. "Oral Sex Within Marriage". Masturbation and Oral Sex: A Christian Approach. Retrieved 8 December 2011.
- For the Strength of Youth: Sexual Purity
- Judaism 101:. "Kosher Sex". Retrieved August 11, 2011.
- Don S. Browning, Martha Christian Green, John Witte. Sex, marriage, and family in world religions. (2006) Columbia University Press. ISBN 0-231-13116-X 
- Abdul Rahman bin Abdul Karim al-Sheha. Islamic Perspective of Sex (2003) Saudi Arabia. ISBN 9960-43-140-1
- Fatima M. D'Oyen. The Miracle of Life. (2007)Islamic Foundation (UK). ISBN 0-86037-355-X
- Thompson, Lady Gwen; Wiccan-Pagan Potpourri; Green Egg, №69; Ostara 1974
- Hans Holzer. The Truth about Witchcraft (1971) Doubleday. page 128. ISBN 0-09-004860-1
- Kenneth E. Bowers. God Speaks Again: An Introduction to the Baha'i Faith. (2004) Baha'i Publishing. ISBN 1-931847-12-6
- John A. Buehrens and Forrest Church. A Chosen Faith: An Introduction to Unitarian Universalism. (1998) Beacon Press. ISBN 0-8070-1617-9
- Hodgkinson, Liz (2002). Peace and Purity: The Story of the Brahma Kumaris a Spiritual Revolution. HCI. pp. 2–29. ISBN 1-55874-962-4.
- Babb, Lawrence A. (1987). Redemptive Encounters: Three Modern Styles in the Hindu Tradition (Comparative Studies in Religion and Society). Oxford University Press. ISBN 0-7069-2563-7. "Sexual intercourse is unnecessary for reproduction because the souls that enter the world during the first half of the Cycle are in possession of a special yogic power (yog bal) by which they conceive children"
- Barrett, David V (2001). The New Believers. Cassell & Co. pp. 265. ISBN 0-304-35592-5.
- Chase, Stacey (July 23, 2006). "The Last Ones Standing". The Boston Globe.
- William Skudlarek. Demythologizing Celibacy: Practical Wisdom from Christian and Buddhist Monasticism. (2008) Liturgical Press. ISBN 0-8146-2947-4
- Naomi R. Cahn, June Carbone (2010). Red families v. blue families: legal polarization and the creation of culture. Oxford University Press US. p. 129. ISBN 0-19-537217-4,. Retrieved July 29, 2011.
- Donald J. Cantor (2006). Same-sex marriage: the legal and psychological evolution in America. Wesleyan University Press. pp. 191 pages. ISBN 0-8195-6812-0,. Retrieved July 29, 2011.
- American Psychological Association (2004). "Resolution on Sexual Orientation and Marriage". Retrieved July 29, 2011.
- American Psychiatric Association (2005). "Support of Legal Recognition of Same-Sex Civil Marriage". Retrieved July 29, 2011.
- K. Smith, Susan (July 30, 2009). "Marriage a Civil Right, not Sacred Rite". The Washington Post. Retrieved July 28, 2011.
- "Decision in Perry v. Schwarzenegger". ecf.cand.uscourts.gov. July 31, 2009. Retrieved July 28, 2011.
- Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). "Chelicerata: Araneae". Invertebrate Zoology (7 ed.). Brooks/Cole. pp. 571–584. ISBN 0-03-025982-7.
|Wikimedia Commons has media related to: Sexual intercourse|
- The International Encyclopedia of Sexuality
- Glossario di Sessuologia clinica – Glossary of clinical sexology
- Janssen, D. F., Growing Up Sexually. Volume I. World Reference Atlas
- Introduction to Animal Reproduction
- Advantages of Sexual Reproduction
- Synonyms for sexual intercourse – the WikiSaurus list of synonyms and slang words for sexual intercourse in many languages