A commentary by Australian researchers highlights the health hazards of nulliparity (the condition of never being pregnant) - hazards they say could be minimized by the birth control pill.
"If the Catholic Church could make the oral contraceptive pill freely available to all its nuns, it would reduce the risk of those accursed pests, cancer of the ovary and uterus, and give nuns' plight the recognition it deserves," Kara Britt of Monash University in Victoria and Roger Short of the University of Melbourne wrote in The Lancet.
The term "accursed pests" was first used to describe breast cancer among nuns by Italian physician Bernadino Ramazzini in 1713. Since then, severe epidemiological studies have confirmed the risk, including a study of more than 31,658 Catholic nuns in the U.S. between 1900 and 1954 that found an increased risk of dying from breast, ovarian and uterine cancer.
Because they don't experience pregnancy or lactation, women who don't have sex have more ovulatory menstrual cycles. That increased number of cycles is directly linked to an increased risk of cancer. But the birth control pill - a form of contraception condemned by the Catholic Church - has been shown to reduce the risk of ovarian and uterine cancer by up to 60 percent.
"The Catholic Church condemns all forms of contraception except abstinence, as outlined by Pope Paul VI in Humanae Vitae in 1968," wrote Britt and Short. "If the Catholic Church could make the oral contraceptive pill freely available to all its nuns, it would reduce the risk of those accursed pests, cancer of the ovary and uterus, and give nuns' plight the recognition it deserves."
But according to Sister Mary Ann Walsh of the U.S. Conference of Catholic Bishops, nuns have the same access to medical care as any other woman - and that includes access to the pill.
"They're presuming the church has some kind of authority over the medical care of nuns, which it doesn't," Walsh told ABC News. "A nun goes to a doctor for her medical care, and if that medical care requires a certain kind of medicine then that medicine is prescribed."
Oral contraceptives can increase the risk of blood clots, a risk thought to be higher in some newer versions of the pill.
"The suggestion that all nuns should take contraception is rather sweeping and almost irresponsible," said Walsh. "There are risks with the pill just as there are risks with doing nothing with regard to uterine and ovarian cancer."
Walsh said the benefits of the pill in reducing cancer risk must be weighed against the side effects.
"A nun's decision needs to be worked out between the nun and her doctor," she said.