Nuns should be given the contraceptive pill to reduce the high death rates from breast, ovarian and uterine cancer that result from their childlessness, say scientists.
Not having children is a risk factor for cancer because pregnancy, as well as breastfeeding a baby, reduces the number of ovulatory cycles a woman has in her lifetime. More ovulatory cycles increases cancer risk.
Women who begin their periods at an early age and hit the menopause late also have a higher risk.
In the first half of the 20th century, scientists who studied nearly 32,000 Catholic nuns in the US established that their death rates from breast, ovarian and uterine cancer were higher than for other women of their age. In 1970, it was formally recognised that the lack of childbearing in nuns raised their breast cancer risk.
The oral contraceptive pill has been shown to have a protective effect. It reduces the overall mortality rates of women who have ever taken it by 12% compared with non-users.
The risk of developing ovarian and endometrial cancers falls by 50%-60% in pill users compared with never-users, protection that persists for 20 years.
There is an increased risk of blood clots, however.
Writing in the Lancet, Dr Kara Britt from Monash University, Melbourne, and Professor Roger Short from the University of Melbourne says nuns should have the option to take the pill.
"The Catholic church condemns all forms of contraception, as outlined by Pope Paul VI in Humanae Vitae in 1968. Although Humanae Vitae never mentions nuns, they should be free to use the contraceptive pill to protect against the hazards of nulliparity since the document states that 'the church in no way regards as unlawful therapeutic means considered necessary to cure organic diseases, even though they also have a contraceptive effect.' If the Catholic church could make the 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," they write.