The Real Reason The Birth Control Pill Was Designed With A 28-Day Cycle

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"Wonderful things can come in small packets," The Economist wrote in 1993 when it named the birth control pill one of the seven wonders of the modern world (via Healthing).

As PBS notes, ever since it was approved by the Food and Drug Administration in 1957 — first as a treatment for menstrual disorders, then in 1960 as a contraceptive — the pill has been hailed as one of humankind's greatest inventions. It allowed women to take control of their reproductive destinies, which in turn helped them stay in school longer and more easily pursue careers.

According to Margaret Sanger, who founded the birth control movement in the United States (per Britannica), "No woman can call herself free who does not own and control her body. No woman can call herself free until she can choose consciously whether she will or will not be a mother."

But the birth control pill was designed with a huge flaw: the 28-day cycle. Many people assume that the pill had to be designed this way, to follow a natural menstrual cycle. In actuality, the cycle's design was all about trying to appease the Catholic Church.

The connection between the birth control pill and the rhythm method

In the 1950s, Harvard obstetrician and gynecologist John Rock collaborated with Gregory Pincus to develop the birth control pill The New Yorker reported. It combined progestin with estrogen to halt ovulation and thus prevent pregnancy. Rock saw the pill as natural since its ingredients mimicked hormones already found in the body. A devoted Roman Catholic, Rock believed that the Vatican would also view the pill as a natural method of birth control, similar to the rhythm method. Pope Pius XII had already approved the use of the rhythm method, in 1951 (per PBS). The Cleveland Clinic explains this method involves tracking menstrual cycles and avoiding sex for a few days before and after ovulation.

"One of the major difficulties with rhythm is that ovulation in many women is not really rhythmic in occurrence. A complete cycle between ovulations may take 25 days on one round, and 32 days the next — depending on innate irregularities in organ functioning as well as one such accidental influences as tension, illness, or simple fatigue," Rock wrote in his book "The Time Has Come: A Catholic Doctor's Proposals to End the Battle Over Birth Control."

By regulating menstrual cycles, Rock reasoned, the birth control pill would make it easier for Catholic couples to use the rhythm method effectively.

The pill's cycle could have been much longer

John Rock and Gregory Pincus decided on a 28-day cycle for the birth control pill: three weeks taking the pill, then one week with either nothing or a placebo. During that week off, the lining of the uterus would slough off.

However, it turns out that Rock and Pincus could have designed the cycle to be almost any length — meaning they could have chosen to drastically increase the length of the cycle and thereby reduce the frequency of menstruation. "In view of the ability of this compound to prevent menstrual bleeding as long as it is taken," Pincus said in 1958 (per The New Yorker), "a cycle of any desired length could presumably be produced."

Professors John Guillebaud and E. Anne MacGregor published a paper in 2018 in BMJ Sexual & Reproductive Health arguing that there is no value to taking a week-long break each month. They wrote, "To make the method seem as 'natural' as possible, women were instructed to stop the hormones for one week out of every four to create a withdrawal bleed. This 7-day interruption in ovarian suppression was not based on scientific evidence but primarily on the belief that women would find a monthly bleed reassuring." 

Guillebaud told The Telegraph, "The gynecologist John Rock devised [the break] because he hoped that the Pope would accept the pill and make it acceptable for Catholics to use."

The Catholic Church ultimately decided against the birth control pill

Despite the best efforts of John Rock and Gregory Pincus to make the pill seem natural, in 1968 Pope Paul VI declared it to be an artificial method of birth control (per PBS). His papal encyclical Humanae Vitae warned what might happen to "responsible men" who used such artificial methods of birth control: "Let them first consider how easily this course of action could open wide the way for marital infidelity and a general lowering of moral standards."

Furthermore, he cautioned in Humanae Vitae that "a man who grows accustomed to the use of contraceptive methods may forget the reverence due to a woman, and, disregarding her physical and emotional equilibrium, reduce her to being a mere instrument for the satisfaction of his own desires, no longer considering her as his partner whom he should surround with care and affection."

Though the Catholic Church sided against the pill, many formulations of the drug still perpetuate the 28-day cycle. Professor John Guillebaud's frustration was evident when he said to The Telegraph in 2019, "How could it be that for 60 years, we have been taking the pill in a sub-optimal way because of this desire to please the Pope?"

Menstruating every month has not been common throughout human history

Anyone who's ever had a period has most likely experienced cramps, headaches, bloating, acne, or mood swings (per Health Digest). "Menstruation, which can be debilitating for some women, is only necessary when women are interested in getting pregnant," Jonathan Eig wrote in "The Birth of the Pill: How Four Crusaders Reinvented Sex and Launched a Revolution."

John Rock and Gregory Pincus imposed the 28-day cycle on the pill in an attempt to make it seem natural — and, by extension, imposed monthly menstruation on anyone taking the pill — but they actually created an unnatural situation. Frequent menstruation has not been the norm throughout human history.

The New Yorker described the work of scientist Beverly Strassmann, who spent two and a half years in the 1980s living with the Dogon tribe in Mali, Africa. To study what menstruation patterns might have looked like in preindustrial societies, she tracked visits to the village's two menstrual huts. Strassmann calculated how often each woman menstruated. According to Strassman's research, the average Dogon woman menstruates 100 times in her life. In comparison, the average lifetime total for a menstruator in a Western country is 350 to 400 times. "It's a pity that gynecologists think that women have to menstruate every month," Strassmann said. "They just don't understand the real biology of menstruation."

Many other birth control options are on the market now

Though there are some unexpected benefits of the pill — such as easing period pain, clearing up acne, and potentially reducing the risk of certain cancers — many arguments can still be made for stopping taking the birth control pill. The pill has been linked to depression, anxiety, and a decreased sex drive, along with an increased risk of breast cancer and stroke.

Fortunately, many alternative birth control options now exist— shots, rings, patches, implants, and more. In particular, an increasing number of women are ditching the pill for IUDs. Intrauterine devices are convenient and effective, they tend to drastically reduce heavy periods, and they can stay in place for years.

Those who choose to stick with the birth control pill no longer need to feel tied to the original 28-day cycle of three weeks on and one week off. The Mayo Clinic outlines different extended-cycle options that are possible, such as 24 days on an active pill followed by four days off, or three months on followed by one week off, or even one full year on active pills, which means no bleeding for a year. That would make most menstruators happy — about 60% of respondents to a 2017 online survey said they would prefer to menstruate less frequently.

Perhaps John Rock should have spent more time speaking to menstruators about what they actually wanted from the birth control pill, and less time thinking about the Pope.