The occurrence of breast cancer is lower among women who have had infertility problems because of an ovulation disorder than among women who have not had difficulty conceiving, according to findings from a study involving more than 116,000 women.

Dr. Kathryn L. Terry of Harvard School of Public Health, Boston and colleagues evaluated data from the Nurses’ Health Study II, which enrolled female nurses aged 25 to 42 years at baseline.

Information on infertility and ovulation was assessed every 2 years starting in 1989, and cases of breast cancer were included through 2001.

During follow-up, 1357 cases of invasive breast cancer were diagnosed, the investigators report in the Archives of Internal Medicine. Overall, women who had ovulatory disorders had a 25 percent lower likelihood of developing breast cancer than those who did not.

Moreover, the risk of breast cancer was lowest in women who underwent induced ovulation for treatment of infertility.

“Our findings are reassuring since many women and their clinicians are concerned about the long-term implications of infertility treatment,” Dr. Terry told Reuters Health.

“However, it is difficult to tease apart the true effect of infertility drugs and infertility, since women who have the most difficultly getting pregnant will most likely be taking infertility drugs the longest,” she added.

SOURCE: Archives of Internal Medicine, December 11/25, 2006.