Combined oral contraceptive pill

# Overview
The Combined Oral Contraceptive Pill (COCP), often referred to as "the Pill", is a combination of an estrogen (oestrogen) and a progestin (progestogen), taken by mouth to inhibit normal fertility. Combined oral contraceptives were developed by Gregory Goodwin Pincus, John Rock, and Min Chueh Chang. They were first approved for contraceptive use in the United States in 1960, and are still a popular form of birth control. They are currently used by more than 100 million women worldwide and by almost 12 million women in the United States. Usage varies widely by country, age, education, and marital status: one quarter of women aged 16  49 in Great Britain currently use the Pill (combined pill or minipill),
compared to only 1% of women in Japan.

# History
By the 1930s, scientists had isolated and determined the structure of the steroid hormones and found that high doses of androgens, estrogens or progesterone inhibited ovulation, 
but obtaining them from European pharmaceutical companies produced from animal extracts was extraordinarily expensive.
In 1939, Russell Marker, a professor of organic chemistry at Pennsylvania State University, developed a method of synthesizing progesterone from plant steroid sapogenins, initially using sarsapogenin from sarsaparilla which proved too expensive. After three years of extensive botanical research he discovered a much better starting material, the aglycone moiety of the saponin, diosgenin, from inedible Mexican wild yams found in the jungles of Veracruz near Orizaba. Unable to interest his research sponsor Parke-Davis in the commercial potential of synthesizing progesterone from Mexican yams, Marker left Penn State and in 1944 co-founded Syntex with two partners in Mexico City before leaving Syntex a year later. Syntex broke the monopoly of European pharmaceutical companies on steroid hormones, reducing the price of progesterone almost 200-fold over the next eight years.
Midway through 20th century, the stage was set for the development of a hormonal contraceptive, but pharmaceutical companies, universities and governments showed no interest in pursuing research.

## Studies of progesterone to prevent ovulation
In early 1951, reproductive physiologist Gregory Pincus, a leader in hormone research and co-founder of the Worcester Foundation for Experimental Biology (WFEB) in Shrewsbury, Massachusetts, first met American birth control movement founder Margaret Sanger at a Manhattan dinner hosted by Abraham Stone, medical director and vice president of Planned Parenthood (PPFA), who helped Pincus obtain a small grant from PPFA to begin hormonal contraceptive research. Research started on April 25, 1951 with reproductive physiologist Min Chueh Chang repeating and extending the 1937 experiments of Makepeace et al. that showed injections of progesterone suppressed ovulation in rabbits. In October 1951, G. D. Searle & Company refused Pincus' request to fund his hormonal contraceptive research, but retained him as a consultant and continued to provide chemical compounds to evaluate.
In March 1952, Sanger wrote a brief note mentioning Pincus' research to her longtime friend and supporter, suffragist and philanthropist Katharine Dexter McCormick, who visited the WFEB and its co-founder and old friend Hudson Hoagland in June 1952 to learn about contraceptive research there. Frustrated when research stalled from PPFA's lack of interest and meager funding, McCormick arranged a meeting at the WFEB on June 6, 1953 with Sanger and Hoagland where she first met Pincus who committed to dramatically expand and accelerate research with McCormick providing fifty times PPFA's previous funding.
Pincus and McCormick enlisted Harvard clinical professor of gynecology John Rock, chief of gynecology at the Free Hospital for Women and an expert in the treatment of infertility, to lead clinical research with women. At a scientific conference in 1952, Pincus and Rock, who had known each other for many years, discovered they were using similar approaches to achieve opposite goals. In 1952, Rock induced a three-month anovulatory "pseudo-pregnancy" state in eighty of his infertility patients with continuous gradually increasing oral doses of estrogen (diethylstilbestrol 5  30 mg/day) and progesterone (50  300 mg/day) and within the following four months an encouraging 15% became pregnant.
In 1953, at Pincus' suggestion, Rock induced a three-month anovulatory "pseudo-pregnancy" state in twenty-seven of his infertility patients with an oral 300 mg/day progesterone-only regimen for 20 days from cycle days 5  24 followed by pill-free days to produce withdrawal bleeding. This produced the same encouraging 15% pregnancy rate during the following four months without the troubling amenorrhea of the previous continuous estrogen and progesterone regimen. But 20% of the women experienced breakthrough bleeding and in the first cycle ovulation was suppressed in only 85% of the women, indicating that even higher and more expensive oral doses of progesterone would be needed to initially consistently suppress ovulation.

## Studies of progestins to prevent ovulation
Pincus asked his contacts at pharmaceutical companies to send him chemical compounds with progestogenic activity. Chang screened nearly 200 chemical compounds in animals and found the three most promising were Syntex's norethindrone and Searle's norethynodrel and norethandrolone.
Chemists Carl Djerassi, Luis Miramontes, and George Rosenkranz at Syntex in Mexico City had synthesized the first orally highly active progestin norethindrone in 1951. Chemist Frank B. Colton at Searle in Skokie, Illinois had synthesized the orally highly active progestins norethynodrel (an isomer of norethindrone) in 1952 and norethandrolone in 1953.
In December 1954, Rock began the first studies of the ovulation-suppressing potential of 5  50 mg doses of the three oral progestins for three months (for 21 days per cycle  days 5  25 followed by pill-free days to produce withdrawal bleeding) in fifty of his infertility patients in Brookline, Massachusetts. 5 mg doses of norethindrone or norethynodrel and all doses of norethandrolone suppressed ovulation but caused breakthrough bleeding, but 10 mg and higher doses of norethindrone or norethynodrel suppressed ovulation without breakthrough bleeding and led to a 14% pregnancy rate in the following five months. Pincus and Rock selected Searle's norethynodrel for the first contraceptive trials in women citing its total lack of androgenicity versus Syntex's norethindrone's very slight androgenicity in animal tests.

## Development of an effective combined oral contraceptive
Norethynodrel (and norethindrone) were subsequently discovered to be contaminated with a small percentage of the estrogen mestranol (an intermediate in their synthesis), with the norethynodrel in Rock's 1954-5 study containing 4-7% mestranol. When further purifying norethynodrel to contain less than 1% mestranol led to breakthrough bleeding, it was decided to intentionally incorporate 2.2% mestranol, a percentage that was not associated with breakthrough bleeding, in the first contraceptive trials in women in 1956. The norethynodrel and mestranol combination was given the proprietary name Enovid.
The first contraceptive trial of Enovid led by Edris Rice-Wray began in April 1956 in Rio Piedras, Puerto Rico. A second contraceptive trial of Enovid (and norethindrone) led by Edward T. Tyler began in June 1956 in Los Angeles. On January 23, 1957, Searle held a symposium reviewing gynecologic and contraceptive research on Enovid through 1956 and concluded Enovid's estrogen content could be reduced by 33% to lower the incidence of estrogenic gastrointestinal side effects without significantly increasing the incidence of breakthrough bleeding.

## Public availability

### United States
On June 10, 1957, the FDA approved Enovid 10 mg (9.85 mg norethynodrel and 150 g mestranol) for menstrual disorders based on data from its use by more than 600 women. Numerous additional contraceptive trials showed Enovid at 10, 5, and 2.5 mg doses to be highly effective. On July 23, 1959, Searle filed a supplemental application to add contraception as an approved indication for 10, 5 and 2.5 mg doses of Enovid. The FDA refused to consider the application until Searle agreed to withdraw the lower dosage forms from the application. On May 9, 1960, the FDA announced it would approve Enovid 10 mg for contraceptive use, which it did on June 23, 1960, by which time Enovid 10 mg had been in general use for three years during which time, by conservative estimate, at least half a million women had used it.
Although FDA-approved for contraceptive use, Searle never marketed Enovid 10 mg as a contraceptive. Eight months later, on February 15, 1961, the FDA approved Enovid 5 mg for contraceptive use. In July 1961, Searle finally began marketing Enovid 5 mg (5 mg norethynodrel and 75 g mestranol) to physicians as a contraceptive.
Although the FDA approved the first oral contraceptive in 1960, contraceptives were not available to married women in all states until Griswold v. Connecticut in 1965 and were not available to unmarried women in all states until Eisenstadt v. Baird in 1972.
The first published case report of a blood clot and pulmonary embolism in a woman using Enavid (Enovid 10 mg in the U.S.) at a dose of 20 mg/day did not appear until November 1961, four years after its approval, by which time it had been used by over one million women. It would take almost a decade of epidemiological studies to conclusively establish an increased risk of venous thrombosis in oral contraceptive users and an increased risk of stroke and myocardial infarction in oral contraceptive users who smoke or have high blood pressure or other cardiovascular or cerebrovascular risk factors. These risks of oral contraceptives were dramatized in the 1969 book The Doctors' Case Against the Pill by feminist journalist Barbara Seaman who helped arrange the 1970 Nelson Pill Hearings called by Senator Gaylord Nelson. The hearings were conducted by Senators who were all men and the witnesses in the first round of hearings were all men, leading Alice Wolfson and other feminists to protest the hearings and generate media attention. Their work led to mandating the inclusion of patient package inserts with oral contraceptives to explain their possible side effects and risks to help facilitate informed consent. Today's standard dose oral contraceptives contain an estrogen dose that is one third lower than the first marketed oral contraceptive and contain lower doses of different, more potent progestins in a variety of formulations.

### Australia
The first oral contraceptive introduced outside the United States was Schering's Anovlar (norethindrone acetate 4 mg + ethinyl estradiol 50 g) on January 1, 1961 in Australia.

### Germany
The first oral contraceptive introduced in Europe was Schering's Anovlar on June 1, 1961 in 

### Britain
Before the mid-1960s, the U.K. did not require pre-marketing approval of drugs. The British Family Planning Association (FPA) through its clinics was then the primary provider of family planning services in Britain and only provided contraceptives that were on its Approved List of Contraceptives (established in 1934). In 1957, Searle began marketing Enavid (Enovid 10 mg in the U.S.) for menstrual disorders. Also in 1957, the FPA established a Council for the Investigation of Fertility Control (CIFC) to test and monitor oral contraceptives which began animal testing of oral contraceptives and in 1960 and 1961 began three large clinical trials in Birmingham, Slough, and London.
In March 1960, the Birmingham FPA began trials of norethynodrel 2.5 mg + mestranol 50 g, but a high pregnancy rate initially occurred when the pills accidentally contained only 36 g of mestranol--the trials were continued with norethynodrel 5 mg + mestranol 75 g (Conovid in Britain, Enovid 5 mg in the U.S.). 
In August 1960, the Slough FPA began trials of norethynodrel 2.5 mg + mestranol 100 g (Conovid-E in Britain, Enovid-E in the U.S.).
In May 1961, the London FPA began trials of Schering's Anovlar.
In October 1961, at the recommendation of the Medical Advisory Council of its CIFC, the FPA added Searle's Conovid to its Approved List of Contraceptives.
On December 4, 1961, Enoch Powell, then Minister of Health, announced that the oral contraceptive pill Conovid could be prescribed through the NHS at a subsidized price of 2s per month.
In 1962, Schering's Anovlar and Searle's Conovid-E were added to the FPA's Approved List of Contraceptives.

### France
On December 28, 1967, the Neuwirth Law legalized contraception in France, including the pill. The pill is the most popular form of contraception in France, especially among young women. The abortion rate has remained stable since the introduction of the pill.

### Japan
In Japan, lobbying from the Japan Medical Association prevented the Pill from being approved for nearly 40 years. Two main objections raised by the association were safety concerns over long-term use of the Pill, and concerns that the Pill use would lead to diminished use of condoms and thereby potentially increase sexually transmitted infection (STI) rates. As of 2004, condoms accounted for 80% of birth control use in Japan, and this may explain Japan's comparably low rates of AIDS.
The Pill was approved for use in September 1999; the Pill prescription guidelines the government endorsed require Pill users to visit a doctor every three months for pelvic examinations and undergo tests for sexually transmitted diseases and uterine cancer. In the United States and Europe, in contrast, an annual or bi-annual clinic visit is standard for Pill users. 

# Use and packaging
Clinical practice guidelines by the U.S. Centers for Disease Control and Prevention, with update focusing on contraception after the use of emergency contraceptive pills and medications to ease insertion of intrauterine devices.
Combined oral contraceptive pills should be taken at the same time each day.  Most brands of combined pills are packaged in one of two different packet sizes, with days marked off for a 28 day cycle. For the 21-pill packet, a pill is consumed daily for three weeks, followed by a week of no pills. For the 28-pill packet, 21 pills are taken, followed by week of placebo or sugar pills. A woman on the pill will have a withdrawal bleed sometime during the placebo week, and is still protected from pregnancy during this week.
Initiation of pills is guided by recommendations from the Clinical practice guidelines by the U.S. Centers for Disease Control and Prevention with succinct, tabular guidance at 
Recommended actions after late or missed pills are provided by the Clinical practice guidelines by the U.S. Centers for Disease Control and Prevention with succinct, flow chart guidance at  . If one or more tablets are forgotten for more than 12 hours, contraceptive protection will be reduced.

## Placebo pills
The purpose of the placebo pills is that the user can take a pill on every day of her menstrual cycle, remaining in this daily habit even during the week without hormones.  Placebo pills may contain an iron supplement, as iron requirements increase during menstruation.
Failure to take pills during the placebo week has no effect on the effectiveness of the pill provided that daily ingestion of active pills is resumed at the end of the week.
The presence of placebo pills is thought to be comforting, as menstruation is a physical confirmation of not being pregnant. The 28-day pill package also simulates the average menstrual cycle, though the hormonal events during a pill cycle are completely different from those of a normal ovulatory menstrual cycle, and the bleeding is triggered by different hormonal cues. Breakthrough bleeding also becomes a more common side effect as a woman attempts to go longer periods of time between menstrual periods.

## Less frequent placebos
If the pill formulation is monophasic, it is possible to skip menstruation and still remain protected against conception by skipping the placebo pills and starting directly with the next packet. Attempting this with bi- or tri-phasic pill formulations carries an increased risk of breakthrough bleeding and may be undesirable. It will not, however, increase the risk of getting pregnant.
Starting in 2003, women have also been able to use a three-month version of the Pill. Similar to the effect of using a constant-dosage formulation and skipping the placebo weeks for three months, Seasonale gives the benefit of less frequent periods, at the potential drawback of breakthrough bleeding. Seasonique is another version in which the placebo week every three months is replaced with a week of low-dose estrogen.
A version of the combined pill has also been packaged to completely eliminate placebo pills and withdrawal bleeds. Marketed as Anya or Lybrel, studies have shown that after seven months 71% of users no longer had any breakthrough bleeding, the most common side effect of going longer periods of time without breaks from active pills.

# Effectiveness
The effectiveness of COCPs, as of most forms of contraception, can be assessed two ways. Perfect use or method effectiveness rates only include people who take the pills consistently and correctly. Actual use, or typical use effectiveness rates are of all COCP users, including those who take the pills incorrectly, inconsistently, or both. Rates are generally presented for the first year of use. Most commonly the Pearl Index is used to calculate effectiveness rates, but some studies use decrement tables.
The typical use pregnancy rate among COCP users varies depending on the population being studied, ranging from 2-8% per year. The perfect use pregnancy rate of COCPs is 0.3% per year.
Several factors account for typical use effectiveness being lower than perfect use effectiveness:
- mistakes on the part of those providing instructions on how to use the method
- mistakes on the part of the user
- conscious user non-compliance with instructions.
For instance, someone using oral forms of hormonal birth control might be given incorrect information by a health care provider as to the frequency of intake, or by mistake not take the pill one day, or simply not bother to go to the pharmacy on time to renew the prescription.
COCPs provide effective contraception from the very first pill if started within five days of the beginning of the menstrual cycle (within five days of the first day of menstruation). If started at any other time in the menstrual cycle, COCPs provide effective contraception only after 7 consecutive days use of active pills, so a backup method of contraception must be used until active pills have been taken for 7 consecutive days. COCPs should be taken at approximately the same time every day.
Contraceptive efficacy may be impaired by: 1) missing more than one active pill in a packet, 2) delay in starting the next packet of active pills (i.e. extending the pill-free, inactive or placebo pill period beyond 7 days), 3) intestinal malabsorption of active pills due to vomiting or diarrhea, 4) drug interactions with active pills that decrease contraceptive estrogen or progestogen levels.

# Mechanism of action
Combined oral contraceptive pills were developed to prevent ovulation by progestogenic and estrogenic suppression of gonadotropin release. Combined hormonal contraceptives, including COCPs, inhibit follicular development and prevent ovulation as their primary mechanism of action.
Progestagen negative feedback decreases the pulse frequency of gonadotropin-releasing hormone (GnRH) release by the hypothalamus, which decreases the release of follicle-stimulating hormone (FSH) and greatly decreases the release of luteinizing hormone (LH) by the anterior pituitary. Decreased levels of FSH inhibit follicular development, preventing an increase in estradiol levels. Progestagen negative feedback and the lack of estrogen positive feedback on LH release prevent a mid-cycle LH surge. Inhibition of follicular development and the absence of a LH surge prevent ovulation.
Estrogen was originally included in oral contraceptives for better cycle control (to stabilize the endometrium and thereby reduce the incidence of breakthrough bleeding), but was also found to inhibit follicular development and help prevent ovulation. Estrogen negative feedback on the anterior pituitary greatly decreases the release of FSH, which inhibits follicular development and helps prevent ovulation.
A secondary mechanism of action of all progestagen-containing contraceptives is inhibition of sperm penetration through the cervix into the upper genital tract (uterus and fallopian tubes) by decreasing the amount of and increasing the viscosity of the cervical mucus.
Other secondary mechanisms have been hypothesized.  One example is endometrial effects that prevent implantation of an embryo in the uterus.  Pro-life groups consider such a mechanism to be abortifacient, and the existence of postfertilization mechanisms is a controversial topic.  Some scientists point out that the possibility of fertilization during COCP use is very small. From this, they conclude that endometrial changes are unlikely to play an important role, if any, in the observed effectiveness of COCPs. Others make more complex arguments against the existence of these mechanisms.  And some scientists argue the existing data supports such mechanisms.  The controversy is currently unresolved.

# Drug interactions
Some drugs reduce the effect of the Pill and can cause breakthrough bleeding, or increased chance of pregnancy. These include drugs such as rifampicin, barbiturates, phenytoin and carbamazepine. In addition cautions are given about broad spectrum antibiotics, such as ampicillin and doxycycline, which may cause problems "by impairing the bacterial flora responsible for recycling ethinylestradiol from the large bowel" (BNF 2003).
The traditional medicinal herb St John's Wort has also been implicated due to its upregulation of the P450 system in the liver.

# Side-effects
Different sources note different incidences of side effects. A University of New Mexico Student Health Center webpage says the majority (about 60%) of women report no side effects at all, and the vast majority of those who do, have only minor effects. A 1992 French review article said that as many as 50% of new first-time users discontinue the Pill before the end of the first year because of nuisance bleeding irregularity side effects such as breakthrough bleeding and amenorrhea.

## Dysfunctional uterine bleeding
Clinical practice guidelines by the U.S. Centers for Disease Control and Prevention note"
- "Unscheduled spotting or bleeding is common during the first 36 months of extended or continuous combined hormonal contraceptive use. It is generally not harmful and decreases with continued combined hormonal contraceptive use.
- If clinically indicated, consider an underlying gynecological problem, such as inconsistent use, interactions with other medications, cigarette smoking, an STD, pregnancy, or new pathologic uterine conditions (e.g., polyps or fibroids). If an underlying gynecological problem is found, treat the condition or refer for care.
If an underlying gynecological problem is not found and the woman wants treatment, the following treatment option can be considered:
- If an underlying gynecological problem is not found and the woman wants treatment, the following treatment option can be considered:
Advise the woman to discontinue combined hormonal contraceptive use (i.e., a hormone-free interval) for 34 consecutive days; a hormone-free interval is not recommended during the first 21 days of using the continuous or extended combined hormonal contraceptive method. A hormone-free interval also is not recommended more than once per month because contraceptive effectiveness might be reduced.
- If unscheduled spotting or bleeding persists and the woman finds it unacceptable, counsel her on alternative contraceptive methods, and offer another method if it is desired."

## Weight
The same 1992 French review article noted that in the subgroup of adolescents 1519 years of age in the 1982 National Survey of Family Growth (NSFG) who had stopped taking the Pill, 2025% reported they stopped taking the Pill because of either acne or weight gain, and another 25% stopped because of fear of cancer. A 1986 Hungarian study comparing two high-dose estrogen (both 50 g ethinyl estradiol) pills found that women using a lower-dose biphasic levonorgestrel formulation (50 g levonorgestrel x 10 days + 125 g levonorgestrel x 11 days) reported a significantly lower incidence of weight gain compared to women using a higher-dose monophasic levonorgestrel formulation (250 g levonorgestrel x 21 days).
Many clinicians consider the public perception of weight gain on the Pill to be inaccurate and dangerous. The aforementioned 1992 French review article noted that one unpublished 1989 study by Professor Elizabeth Connell at Emory University of 550 women found that 23% of the 6% of women who discontinued the Pill because of poor cycle control experienced subsequent unwanted pregnancies. A 2000 British review article concluded there is no evidence that modern low-dose pills cause weight gain, but that fear of weight gain contributed to poor compliance in taking the Pill and subsequent unintended pregnancy, especially among adolescents.

## Sexuality
The Pill may have a positive effect on a woman's sexuality. Because neither the woman (who uses the Pill) nor her partner need take any special action before or during intercourse, it makes birth control "invisible" and sex spontaneous, more natural, or both.
However, some say the Pill can also have a negative effect on a woman's sexuality. Dr. John Bancroft (a senior research fellow at the Kinsey Institute at Indiana University) estimates that one in four women on the pill experience some negative sexual effect. These effects may include a decreased frequency of sexual thoughts, increased difficulty in becoming aroused, or decreased lubrication, which can make sex painful. Recent research co-authored by Dr. Irwin Goldstein (a urologist in Boston) suggests such effects may continue for up to four months after a woman stops taking the Pill.

## Depression
Low levels of serotonin, a neurotransmitter in the brain, have been linked to depression. High levels of estrogen, as in first-generation COCPs, and progestin, as in some progestin-only contraceptives, have been shown to promote the lowering of brain serotonin levels by increasing the concentration of a brain enzyme that reduces serotonin. Progestin-only contraceptives are known to worsen the condition of women who are already depressed.
Current medical reference textbooks on contraception and major organizations such as the American ACOG, the WHO, and the United Kingdom's RCOG agree that current evidence indicates low-dose oral contraceptives are unlikely to increase the risk of depression, and unlikely to worsen the condition in women who are currently depressed. Contraceptive Technology states that low-dose COCPs have not been implicated in disruptions of serotonin or tryptophan.
However, a recent study found that women taking the oral contraceptive pill are almost twice as likely to be depressed than those not on the Pill. Professor Jayashri Kulkarni from the School of Psychology, Psychiatry and Psychological Medicine at Monash University conducted a study with 62 women. In the study depression symptom scores between users and non-users of combined oral contraceptives were compared. Those that used the Pill had an average depression rating scale score that was 17.6, compared with 9.8 for the non-users. Women in the survey were aged over 18 years, were not pregnant or lactating, had no history of clinical depression and had not used anti-depressant medication for the previous 12 months. The relationship to depression and the Pill in the is study has been described as significant by the researcher.

## Other effects
Other possible side effects are: vaginal discharge, changes in menstrual flow, breakthrough bleeding, nausea, vomiting, headaches, changes in the breasts, changes in blood pressure, loss of scalp hair, skin problems and skin improvements. The insert included with each pill packet usually has a more extensive list of recognized side effects.

# Formulations
Oral contraceptives come in a variety of formulations. The main division is between combined oral contraceptive pills, containing both estrogen and progestins and progestin only pills. Combined oral contraceptive pills also come in varying types, including varying doses of estrogen, and whether the dose of estrogen or progestin changes from week to week.

# Cautions and contraindications
Oral contraceptives may influence coagulation, increasing the risk of deep venous thrombosis (DVT) and pulmonary embolism, stroke and myocardial infarction (heart attack). Combined oral contraceptives are generally accepted to be contraindicated in women with pre-existing cardiovascular disease, in women who have a familial tendency to form blood clots (such as familial factor V Leiden), women with severe obesity and/or hypercholesterolaemia (high cholesterol level), and in smokers over age 35.
Research into the relationship between breast cancer risk and hormonal contraception is complex and seemingly contradictory.
The large 1996 collaborative reanalysis of individual data on over 150,000 women in 54 studies of breast cancer found that: "The results provide strong evidence for two main conclusions. First, while women are taking combined oral contraceptives and in the 10 years after stopping there is a small increase in the relative risk of having breast cancer diagnosed. Second, there is no significant excess risk of having breast cancer diagnosed 10 or more years after stopping use. The cancers diagnosed in women who had used combined oral contraceptives were less advanced clinically than those diagnosed in women who had never used these contraceptives."
This data has been interpreted to suggest that oral contraceptives have little or no biological effect on breast cancer development, but that women who seek gynecologic care to obtain contraceptives have more early breast cancers detected through screening.
It is generally accepted by medical authorities that the health risks of oral contraceptives are lower than those from pregnancy and birth, and "the health benefits of any method of contraception are far greater than any risks from the method". Some organizations have argued that comparing a contraceptive method to no method (pregnancy) is not relevant - instead, the comparison of safety should be among available methods of contraception.

# Non-contraceptive uses
The hormones in "the Pill" can be used to treat some medical conditions, such as polycystic ovary syndrome (PCOS), endometriosis, adenomyosis, anemia related to menstruation, and painful menstruation (dysmenorrhea). In addition, oral contraceptives are often prescribed as medication for mild or moderate acne. The pill can also induce menstruation on a regular schedule for women bothered by irregular menstrual cycles and certain disorders where there is dysfunctional uterine bleeding.
Combined oral contraceptive use reduces the risk of ovarian cancer by 40% and the risk of endometrial cancer by 50% compared to never users. The risk reduction increases with duration of use, with an 80% reduction in risk for both ovarian and endometrial cancer with use for more than 10 years. The risk reduction for both ovarian and endometrial cancer persists for at least 20 years.

# Social and cultural impact
While the Pill was approved by the FDA in the early 1960s, its use was limited to married women. It was only in the early 1970s, when the "age of majority" legally changed from 21 to 18, that the Pill truly became widespread. As its use diffused to even those young and non-married women, it generated an enormous social impact. In the first place, it was far more effective than any previous method of birth control, giving women unprecedented control over their fertility. Its use was separate from intercourse, requiring no special preparations at the time of sexual activity that might interfere with spontaneity or sensation, and the choice to take the Pill was a private one. This combination of factors served to make the Pill immensely popular within a few years of its introduction.  
Claudia Goldin, among others, argue that this new contraceptive technology was a key player in forming women's modern economic role, in that it prolonged the age at which women first married allowing them to invest in education and other forms of human capital as well as generally become more career-oriented.
Because the Pill was so effective, and soon so widespread, it also heightened the debate about the moral and health consequences of pre-marital sex and promiscuity. Never before had sexual activity been so divorced from reproduction. For a couple using the Pill, intercourse became purely an expression of love, or a means of physical pleasure, or both; but it was no longer a means of reproduction. While this was true of previous contraceptives, their relatively high failure rates and their less widespread use failed to emphasize this distinction as clearly as did the Pill. The spread of oral contraceptive use thus led many religious figures and institutions to debate the proper role of sexuality and its relationship to procreation. The Roman Catholic Church in particular, after studying the phenomenon of oral contraceptives, re-emphasized traditional Catholic teaching on birth control in the 1968 papal encyclical Humanae Vitae. The encyclical reiterated the traditional Catholic teaching that artificial contraception distorted the nature and purpose of sex.
A backlash against oral contraceptives occurred in the early and mid-1970s, when reports and speculations appeared that linked the use of the Pill to breast cancer. Until then, many women in the feminist movement had hailed the Pill as an "equalizer" that had given them the same sexual freedom as men had traditionally enjoyed. This new development, however, caused many of them to denounce oral contraceptives as a male invention designed to facilitate male sexual freedom with women at the cost of health risk to women.
At the same time, society was beginning to take note of the impact of the Pill on traditional gender roles. Women now did not have to choose between a relationship and a career; singer Loretta Lynn commented on this in her 1974 album with a song entitled "The Pill", which told the story of a married woman's use of the drug to liberate herself from her traditional role as wife and mother.

# Environmental impact
Human excretion in urine and feces of the natural estrogens estrone and estradiol and excretion of the synthetic estrogen ethinylestradiol by women using COCPs are likely to play a role in causing endocrine disruption in wild fish populations in some segments of streams contaminated by treated sewage effluents. 
A review of activated sludge plant performance found estrogen removal rates varied considerably but averaged 78% for estrone, 91% for estradiol, and 76% for ethinylestradiol (estriol effluent concentrations are between those of estrone and estradiol, but estriol is a much less potent endocrine disruptor to fish). 
Effluent concentrations of ethinylestradiol are lower than estradiol which are lower than estrone, but ethinylestradiol is more potent than estradiol which is more potent than estrone in the induction of intersex fish and synthesis of vitellogenin in male fish.

# Footnotes
-  "Dr. Pincus, Developer of Birth-Control Pill, Dies". New York Times. August 23, 1967. Retrieved 2007-07-21. Dr. Gregory Goodwin Pincus, one of the three "fathers" of the birth-control pill, died here tonight at Peter Bent Brigham Hospital of myeloid metaplasia, a rare blood disease. He was 64 years old and lived in Northboro..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"\"""\"""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{display:none;font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
-  Jump up to: 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Hatcher, Robert A.; Nelson, Anita (2004). "Combined Hormonal Contraceptive Methods".  In in Hatcher, Robert A. (ed.). Contraceptive Technology (18th rev. ed. ed.). New York: Ardent Media. pp. pp. 391-460. ISBN 0-966-49025-8.CS1 maint: Multiple names: authors list (link) CS1 maint: Extra text: editors list (link) CS1 maint: Extra text (link)
-  Mosher WD, Martinez GM, Chandra A, Abma JC, Willson SJ (2004). "Use of contraception and use of family planning services in the United States: 1982-2002" (PDF). Adv Data (350): 136. PMID 15633582.CS1 maint: Multiple names: authors list (link)  all US women aged 15-44
-  UN Population Division (2006). World Contraceptive Use 2005 (PDF). New York: United Nations. ISBN 9-211-51418-5. women aged 15-49 married or in consensual union
-  Taylor, Tamara; Keyse, Laura; Bryant, Aimee (2006). Contraception and Sexual Health, 2005/06 (PDF). London: Office for National Statistics. ISBN 1-85774-638-4.CS1 maint: Multiple names: authors list (link)  British women aged 16-49: 24% currently use the Pill (17% use Combined pill, 5% use Minipill, 2% don't know type)
-  Jump up to: 6.0 6.1 6.2 Aiko Hayashi (August 20, 2004). "Japanese Women Shun The Pill". CBS News. Retrieved 2006-06-12.
-  Goldzieher JW, Rudel HW (1974). "How the oral contraceptives came to be developed". JAMA. 230 (3): 4215. PMID 4606623.
-  Goldzieher JW (1982). "Estrogens in oral contraceptives: historical perspective". Johns Hopkins Med J. 150 (5): 1659. PMID 7043034.
-  Perone N (1993). "The history of steroidal contraceptive development: the progestins". Perspect Biol Med. 36 (3): 34762. PMID 8506121.
-  Goldzieher JW (1993). "The history of steroidal contraceptive development: the estrogens". Perspect Biol Med. 36 (3): 3638. PMID 8506122.
-  Jump up to: 11.0 11.1 11.2 11.3 Maisel, Albert Q. (1965). The Hormone Quest. New York: Random House.
-  Jump up to: 12.0 12.1 Asbell, Bernard (1995). The Pill : A Biography of the Drug That Changed the World. New York: Random House. ISBN 0-679-43555-7.
-  Lehmann PA, Bolivar A, Quintero R (1973). "Russell E. Marker. Pioneer of the Mexican steroid industry". J Chem Educ. 50: 1959. PMID 4569922. Text "issue-3 " ignored (help)CS1 maint: Multiple names: authors list (link)
-  Jump up to: 14.0 14.1 Vaughan, Paul (1970). The Pill on Trial. New York: Coward-McCann.
-  Jump up to: 15.0 15.1 15.2 Tone, Andrea (2001). Devices & Desires : A History of Contraceptives in America. New York: Hill and Wang. ISBN 0-809-03817-X.
-  Jump up to: 16.0 16.1 16.2 16.3 Reed, James (1978). From Private Vice to Public Virtue : The Birth Control Movement and American Society Since 1830. New York: Basic Books. ISBN 0-465-02582-X.
-  Jump up to: 17.0 17.1 McLaughlin, Loretta (1982). The pill, John Rock, and the Church : The Biography of a Revolution. Boston: Little, Brown. ISBN 0-316-56095-2.
-  Jump up to: 18.0 18.1 18.2 18.3 18.4 Marks, Lara V (2001). Sexual Chemistry : A History of the Contraceptive Pill. New Haven: Yale University Press. ISBN 0-300-08943-0.
-  Jump up to: 19.0 19.1 19.2 19.3 19.4 19.5 Watkins, Elizabeth Siegel (1998). On the Pill : A Social History of Oral Contraceptives, 1950-1970. Baltimore: Johns Hopkins University Press. ISBN 0-801-85876-3.
-  Jump up to: 20.0 20.1 20.2 20.3 20.4 20.5 20.6 20.7 20.8 Speroff, Leon; Darney, Philip D. (2005). "Oral Contraception". A Clinical Guide for Contraception (4th ed. ed.). Philadelphia: Lippincott Williams & Wilkins. pp. pp. 21-138. ISBN 0-781-76488-2.CS1 maint: Multiple names: authors list (link) CS1 maint: Extra text (link)
-  Djerassi, Carl (2001). This man's pill : reflections on the 50th birthday of the pill. Oxford: Oxford University Press. pp. pp. 11-62. ISBN 0198508727.CS1 maint: Extra text (link)
-  Applezweig, Norman (1962). Steroid drugs. New York: Blakiston Division, McGraw-Hill. pp. pp. vii-xi, 983.CS1 maint: Extra text (link)
-  Gereffi, Gary (1983). The pharmaceutical industry and dependency in the Third World. Princeton: Princeton University Press. pp. pp. 53-163. ISBN 0691094012.CS1 maint: Extra text (link)
-  Fields, Armond (2003). Katharine Dexter McCormick : Pioneer for Women's Rights. Westport: Prager. ISBN 0-275-98004-9.
-  Rock J, Garcia CR, Pincus G (1957). "Synthetic progestins in the normal human menstrual cycle". Recent Prog Horm Res. 13: 32339. PMID 13477811.CS1 maint: Multiple names: authors list (link)
-  Pincus G (1958). "The hormonal control of ovulation and early development". Postgrad Med. 24 (6): 65460. PMID 13614060.
-  Chang MC (1978). "Development of the oral contraceptives". Am J Obstet Gynecol. 132 (2): 2179. PMID 356615.
-  Garcia CR, Pincus G, Rock J (1956). "Effects of certain 19-nor steroids on the normal human menstrual cycle". Science. 124 (3227): 8913. PMID 13380401.CS1 maint: Multiple names: authors list (link)
-  Jump up to: 29.0 29.1 Rock, John; Garcia, Celso R. (1957). "Observed effects of 19-nor steroids on ovulation and menstruation".  In in. Proceedings of a Symposium on 19-Nor Progestational Steroids. Chicago: Searle Research Laboratories. pp. pp. 14-31.CS1 maint: Multiple names: authors list (link) CS1 maint: Extra text (link)
-  Pincus G, Rock J, Garcia CR, Rice-Wray E, Paniagua M, Rodgriquez I (1958). "Fertility control with oral medication". Am J Obstet Gynecol. 75 (6): 133346. PMID 13545267.CS1 maint: Multiple names: authors list (link)
-  Jump up to: 31.0 31.1 31.2 31.3 31.4 Junod SW, Marks L (2002). "Women's trials: the approval of the first oral contraceptive pill in the United States and Great Britain" (PDF). J Hist Med Allied Sci. 57: 11760. PMID 11995593. Text "issue-2 " ignored (help)
-  Ramirez de Arellano, Annette B.; Seipp, Conrad (1983). Colonialism, Catholicism, and Contraception : A History of Birth Control in Puerto Rico. Chapel Hill: University of North Carolina Press. ISBN 0-807-81544-6.CS1 maint: Multiple names: authors list (link)
-  Rice-Wray, Edris (1957). "Field Study with Enovid as a Contraceptive Agent".  In in. Proceedings of a Symposium on 19-Nor Progestational Steroids. Chicago: Searle Research Laboratories. pp. pp. 78-85.CS1 maint: Extra text (link)
-  Tyler ET, Olson HJ (1959). "Fertility promoting and inhibiting effects of new steroid hormonal substances". JAMA. 169 (16): 184354. PMID 13640942.
-  Winter IC (1957). "Summary".  In in. Proceedings of a Symposium on 19-Nor Progestational Steroids. Chicago: Searle Research Laboratories. pp. pp. 120-2.CS1 maint: Extra text (link)
-  Winter IC (1970). "Industrial pressure and the population problem--the FDA and the pill". JAMA. 212 (6): 10678. PMID 5467404.
-  Winter IC (1965). "The incidence of thromboembolism in Enovid users". Metabolism. 14 (Suppl): 4228. PMID 14261427.
-  Jordan WM, Anand JK (1961). "Pulmonary embolism". Lancet. 278 (7212): 11467.
-  Seaman, Barbara (1969). The Doctors Case Against the Pill. New York: P. H. Wyden.
-  FDA (1970). "Statement of Policy Concerning Oral Contraceptive Labeling Directed to Users". Fed Regist. 35 (113): 90013. Unknown parameter |month= ignored (help)
-  FDA (1978). "Oral Contraceptives; Requirement for Labeling Directed to the Patient". Fed Regist. 43 (21): 431334. Unknown parameter |month= ignored (help)
-  FDA (1989). "Oral Contraceptives; Patient Package Insert Requirement". Fed Regist. 54 (100): 225858. Unknown parameter |month= ignored (help)
-  Jump up to: 43.0 43.1 "History of Schering AG". Ernst Schering Foundation. Retrieved 2007-12-05.
-  Mears E (1961). "Clinical trials of oral contraceptives". Br Med J. 2 (5261): 117983. PMID 14471934.
-  Eckstein P, Waterhouse JA, Bond GM, Mills WG, Sandilands DM, Shotton DM (1961). "The Birmingham oral contraceptive trial". Br Med J. 2 (5261): 11729. PMID 13889122.CS1 maint: Multiple names: authors list (link)
-  Jump up to: 46.0 46.1 Pullen D (1962). ""Conovid-E" as an oral contraceptive". Br Med J. 2 (5311): 10169. PMID 13972503.
-  Jump up to: 47.0 47.1 Mears E, Grant EC (1962). ""Anovlar" as an oral contraceptive". Br Med J. 2 (5297): 759. PMID 14471933.
-  "Annotations: Pill at F.P.A. clinics". Br Med J. 2 (5258): 1009. 1961. Unknown parameter |month= ignored (help)
                        "Medical news: Oral contraceptives and the F.P.A." Br Med J. 2 (5258): 1032. 1961. Unknown parameter |month= ignored (help)
-  "Medical News: Contraceptive Pill". Br Med J. 2 (5266): 1584. 1961. Unknown parameter |month= ignored (help)
 "Subsidizing birth control". Time. 78 (24): 55. 1961. Unknown parameter |month= ignored (help)
-  Dourlen Rollier, AV (1972). "Contraception: yes, but...". Fertilite, orthogenie. 4 (4). PMID 12306278.
-  "The Aids Generation: the pill takes priority?". Science Actualities. 2000. Retrieved 2006-09-07.
-  "Djerassi on birth control in Japan - abortion 'yes,' pill 'no'" (Press release). Stanford University News Service. 96-14-02. Retrieved 2006-08-23. Check date values in: |date= (help)
-  Jump up to: 53.0 53.1 53.2 53.3 Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention (CDC) (2013). "U.S. Selected Practice Recommendations for Contraceptive Use, 2013: adapted from the World Health Organization selected practice recommendations for contraceptive use, 2nd edition". MMWR Recomm Rep. 62 (RR-05): 160. PMID 23784109.CS1 maint: Multiple names: authors list (link)
-  Centers for Disease Control and Prevention (2016). Selected Practice Recommendations for Contraceptive Use
-  Organon (2001). "Mercilon SPC (Summary of Product Characteristics". Retrieved 2007-04-07. Unknown parameter |month= ignored (help)
-  "FDA Approves Seasonale Oral Contraceptivel". September 25, 2003. Retrieved 2006-11-09. Unknown parameter |coauthors= ignored (help)
-  Wheldon, Julie (2005-12-28). "New Pill will eliminate menstruation". Daily Mail. Retrieved 2006-12-23. Check date values in: |date= (help)
-  Kippley, John (1996). The Art of Natural Family Planning (4th addition ed.). Cincinnati, OH: The Couple to Couple League. pp. p.141. ISBN 0-926412-13-2. Unknown parameter |coauthors= ignored (help)CS1 maint: Extra text (link)
-  FFPRHC (2007). "Clinical Guidance: First Prescription of Combined Oral Contraception" (PDF). Retrieved 2007-06-26.
-  Jump up to: 60.0 60.1 60.2 Loose, Davis S.; Stancel, George M. (2006). "Estrogens and Progestins".  In Brunton, Laurence L.; Lazo, John S.; Parker, Keith L. (eds.). Goodman & Gilman's The Pharmacological Basis of Therapeutics (11th ed. ed.). New York: McGraw-Hill. pp. pp. 1541-1571. ISBN 0-07-142280-3.CS1 maint: Multiple names: authors list (link) CS1 maint: Extra text: editors list (link) CS1 maint: Extra text (link)
-  Glasier, Anna (2006). "Contraception".  In DeGroot, Leslie J.; Jameson, J. Larry (eds.). Endocrinology (5th edition ed.). Philadelphia: Elsevier Saunders. pp. pp. 2993-3003. ISBN 0-7216-0376-9.CS1 maint: Multiple names: editors list (link) CS1 maint: Extra text: editors list (link) CS1 maint: Extra text (link)
-  Jump up to: 62.0 62.1 62.2 Rivera R, Yacobson I, Grimes D (1999). "The mechanism of action of hormonal contraceptives and intrauterine contraceptive devices". Am J Obstet Gynecol. 181 (5 Pt 1): 12639. PMID 10561657.CS1 maint: Multiple names: authors list (link)
-  Template:Cite paper
-  Larimore WL, Stanford JB (2000). "Postfertilization effects of oral contraceptives and their relationship to informed consent" (PDF). Arch Fam Med. 9 (2): 12633. PMID 10693729. Retrieved 2008-02-26.
-  The effects of broad-spectrum antibiotics on Combined contraceptive pills is not found on systematic interaction metanalysis (Archer, 2002), although "individual patients do show large decreases in the plasma concentrations of ethinylestradiol when they take certain other antibiotics" (Dickinson, 2001). "...experts on this topic still recommend informing oral contraceptive users of the potential for a rare interaction" (DeRossi, 2002) and this remains current (2006) UK Family Planning Association advice.
Archer J, Archer D (2002). "Oral contraceptive efficacy and antibiotic interaction: a myth debunked". J Am Acad Dermatol. 46 (6): 91723. PMID 12063491.
Dickinson B, Altman R, Nielsen N, Sterling M (2001). "Drug interactions between oral contraceptives and antibiotics". Obstet Gynecol. 98 (5 Pt 1): 85360. PMID 11704183.CS1 maint: Multiple names: authors list (link) 
DeRossi S, Hersh E (2002). "Antibiotics and oral contraceptives". Dent Clin North Am. 46 (4): 65364. PMID 12436822.
- Archer J, Archer D (2002). "Oral contraceptive efficacy and antibiotic interaction: a myth debunked". J Am Acad Dermatol. 46 (6): 91723. PMID 12063491.
- Dickinson B, Altman R, Nielsen N, Sterling M (2001). "Drug interactions between oral contraceptives and antibiotics". Obstet Gynecol. 98 (5 Pt 1): 85360. PMID 11704183.CS1 maint: Multiple names: authors list (link)
- DeRossi S, Hersh E (2002). "Antibiotics and oral contraceptives". Dent Clin North Am. 46 (4): 65364. PMID 12436822.
-  "The Pill: Side Effects & Current Issues". University of New Mexico Student Health Center. Retrieved 2006-10-17.
-  Jump up to: 67.0 67.1 67.2 Serfaty D (1992). "Medical aspects of oral contraceptive discontinuation". Adv Contracept. 8 (Suppl 1): 2133. PMID 1442247.
Sanders, Stephanie A. (July 2001). "A prospective study of the effects of oral contraceptives on sexuality and well-being and their relationship to discontinuation". Contraception. 64 (1): 5158. Retrieved 2007-03-02. Unknown parameter |coauthors= ignored (help)
-  Balogh A (1986). "Clinical and endocrine effects of long-term hormonal contraception". Acta Med Hung. 43 (2): 97102. PMID 3588164.
-  Gupta S (2000). "Weight gain on the combined pill--is it real?". Hum Reprod Update. 6 (5): 42731. PMID 11045873.
-  "Less Sexual Desire After The Pill?". WebMD. CBS News. January 3, 2006. Retrieved 2008-03-14.
-  Template:Cite paper, which cites:
Kulkarni J, Liew J, Garland K (2005). "Depression associated with combined oral contraceptives--a pilot study". Aust Fam Physician. 34 (11): 990. PMID 16299641.CS1 maint: Multiple names: authors list (link)
-  ACOG (2006). "Practice bulletin No. 73: Use of hormonal contraception in women with coexisting medical conditions". Obstet Gynecol. 107 (6): 145372. PMID 16738183.
-  WHO (2004). "Low-dose combined oral contraceptives". Medical Eligibility Criteria for Contraceptive Use (3rd ed. ed.). Geneva: Reproductive Health and Research, WHO. ISBN 92-4-156266-8.CS1 maint: Extra text (link)
-  FFPRHC (2006). "The UK Medical Eligibility Criteria for Contraceptive Use (2005/2006)" (PDF). Retrieved 2007-03-31.
-  Kulkarni, Jayashri (2005-03-01). "Contraceptive Pill Linked to Depression". Monash Newsline. Retrieved 2007-10-29.
-  FPA (2005). "The combined pill - Are there any risks?". Family Planning Association (UK). Retrieved 2007-01-08. Unknown parameter |month= ignored (help)
-  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): 171327. PMID 8656904.
-  Collaborative Group on Hormonal Factors in Breast Cancer (1996). "Breast cancer and hormonal contraceptives: further results". Contraception. 54 (3 Suppl): 1S106S. PMID 8899264.
-  Plu-Bureau G, Le M (1997). "Oral contraception and the risk of breast cancer". Contracept Fertil Sex. 25 (4): 3015. PMID 9229520. - pooled re-analysis of original data from 54 studies representing about 90% of the published epidemiological studies, prior to introduction of third generation pills.
-  Crooks, Robert L. and Karla Baur (2005). Our Sexuality. Belmont, CA: Thomson Wadsworth. ISBN 0-534-65176-3.
-  WHO (2005). Decision-Making Tool for Family Planning Clients and Providers Appendix 10: Myths about contraception
-  Holck, Susan. "Contraceptive Safety". Special Challenges in Third World Women's Health. 1989 Annual Meeting of the American Public Health Association. Retrieved 2006-10-07.
-  Huber J, Walch K (2006). "Treating acne with oral contraceptives: use of lower doses". Contraception. 73 (1): 239. PMID 16371290.
-  George Weigel (2002). The Courage to Be Catholic: Crisis, Reform, and the Renewal of the Church. Basic Books.
-  Andrea Dworkin (1976). Our Blood: Prophecies and Discourses on Sexual Politics. Harper & Row.
-  Williams RJ, Johnson AC, Smith JJ, Kanda R (2003). "Steroid estrogens profiles along river stretches arising from sewage treatment works discharges". Environ Sci Technol. 37 (9): 174450. PMID 12775044.CS1 maint: Multiple names: authors list (link)
-  Jobling S, Williams R, Johnson A, Taylor A, Gross-Sorokin M, Nolan M, Tyler CR, van Aerle R, Santos E, Brighty G (2006). "Predicted exposures to steroid estrogens in U.K. rivers correlate with widespread sexual disruption in wild fish populations" (PDF). Environ Health Perspect. 114 (Suppl 1): 329. PMID 16818244.CS1 maint: Multiple names: authors list (link)
-  Johnson AC, Williams RJ, Simpson P, Kanda R (2007). "What difference might sewage treatment performance make to endocrine disruption in rivers?". Environ Pollut. 147 (1): 194202. PMID 17030080.CS1 maint: Multiple names: authors list (link)
-  Johnson AC, Williams RJ (2004). "A model to estimate influent and effluent concentrations of estradiol, estrone, and ethinylestradiol at sewage treatment works". Environ Sci Technol. 38 (13): 364958. PMID 15296317.