"First there’s Rock, a Harvard fertility expert and a developer of the pill. There’s a longstanding myth that Rock, a Catholic, designed the pill in the 1950s with the church in mind and included a week of hormonal withdrawal — and therefore bleeding — to make his invention seem more natural. In fact, the thought never crossed his mind, the Rutgers University historian Margaret Marsh says. Instead, it was Gregory (Goody) Pincus, the other developer of the pill, who suggested that the pill be given as a 20-days-on, 5-days-off regimen. Pincus wanted to provide women in his trials with reassurance that they weren’t pregnant, and to know himself that the pill was working as a contraceptive. Rock agreed. After the F.D.A. approved the pill in 1960, however, those few days of light bleeding took on a new significance. Anticipating the church’s opposition, Rock became not just a researcher but also an advocate. In his 1963 book “The Time Has Come: A Catholic Doctor’s Proposals to End the Battle Over Birth Control,” he argued that the pill was merely a scientific extension of the church-sanctioned “rhythm method.” It “completely mimics” the body’s own hormones, he wrote, to extend the “safe period” in which a woman could have intercourse and not become pregnant. “It must be emphasized that the pills, when properly taken, are not at all likely to disturb menstruation,” he wrote. “It has been my consistent feeling that, when properly used for conception control, they merely serve as adjuncts to nature.” He was stretching the truth. Rock knew that the pill’s synthetic hormones caused the lining of a woman’s uterus to thin out, making it inhospitable for a fertilized egg. During the off week, when the hormones were withdrawn, her body got the signal that it was time to shed the lining. But because this event didn’t involve ovulation, it was better described as withdrawal bleeding than menstruation."