The pope, the pill and the court Last week, the Supreme Court ruled that a group of Colorado nuns will not be required to offer contraceptive coverage to employees while pursuing its legal challenge to the Affordable Care Act. The nuns' action highlights the misunderstandings and theological errors behind the Vatican's condemnation of what it terms "artificial contraception." And it also overlooks an important medical point: The nuns might have something to gain from taking oral contraceptives. But first, some background on the history of contraception. When the pill was invented in Massachusetts in the 1950s, it was still illegal to use any form of contraceptive in that state. John Rock, a Boston OB-GYN and a devout Roman Catholic, was selected to conduct some of the first clinical trials, and he quickly became a fan of the new method, seeing no reason it would be inappropriate for Catholic women. He argued that this new method of contraception simply imitated nature by reproducing the pattern of hormones found during breastfeeding, which inhibits conception. In support of his argument, Rock wrote the 1963 treatise "The Time has Come," subtitled, "A Catholic Doctor's Proposals to End the Battle over Birth Control." In it, he argued that birth control pills, by suppressing ovulation, were actually more in line with Catholic theology than the rhythm method, since the rhythm method meant that eggs went deliberately unfertilized, whereas with oral contraceptives, there were no eggs. For a time, it looked as if his arguments might carry the day. The 1960s were a time of reevaluation in the Roman Catholic Church. Pope John XXIII launched Vatican II and established a Pontifical Commission on Birth Control. In 1966, the commission issued its report, concluding that oral contraceptives were "not intrinsically evil." The commissioners pointed out that "it is natural to man to use his skill in order to put under human control what is given by physical nature." But by then, there was a new pope, Paul VI. Paul VI spent two years deciding whether to accept or reject the commission's findings. In 1968, he issued the encyclical Humanae Vitae (Of Human Life). Instead of accepting oral contraceptives as natural and allowing their use, Paul VI concluded that "any action which either before, at the moment of, or after sexual intercourse, is specifically intended to prevent procreation - whether as an end or as a means," was prohibited for Catholics. Many theologians, priests and, above all, married Catholics rejected Humanae Vitae. John Rock stopped going to Mass. But the archaic ban on contraception remains church doctrine. Humanae Vitae did contain one bit of common sense: It permitted "therapeutic means considered necessary to cure organic diseases even though they have a contraceptive effect." Now, after two generations have used the pill, we know that it does have significant therapeutic properties. Even a few years of oral contraceptive have been shown to lead to a substantial reduction in ovarian and uterine cancer later in life. There's no change in breast cancer, which is neither more nor less common among women who have used the pill. And are the pills really unnatural? Our hunter-gatherer ancestors had their babies four or five years apart, because of long intervals of breastfeeding. As a result of that and their shorter life spans, they had as few as 40 menstrual cycles in a lifetime, while a modern woman can have 400. Though we can't claim that today's pills are perfect, their use is certainly less unnatural than enduring the hormone turmoil of hundreds of menstrual cycles. This brings us back to the Colorado nuns, the Little Sisters of the Poor. Nuns have a substantially higher risk of reproductive cancers than women who have children, in part because of their celibacy, which means a lifetime of uninterrupted menstrual cycles. In 2011, my wife and I attended an obstetric conference in the Pontifical University of the Holy Cross in Rome. The keynote lecture there recommended that nuns use oral contraceptives for two or three years after taking their vows, in order to benefit from a long-term reduction in reproductive cancers to which nuns are otherwise exposed by their celibate life. It was not a joke but, rather, impeccable science. More than 1 million U.S. women already take the pill for its health benefits rather than its contraceptive effect. Members of the Little Sisters of the Poor are sincere and intelligent women with admirable goals, but they are asking the Supreme Court to exempt them from covering a medicine that would benefit their health. John Rock had it right, and Pope Paul VI made a terrible mistake. Will Pope Francis have the good sense to reverse Humanae Vitae? Malcolm Potts is an obstetrician and reproductive scientist and a professor of public health at UC Berkeley.