The causes of ovarian cancer are murky, although many risk factors are well known. One of those is that women who've never had children are at a higher risk. Some researchers have wondered whether many of those women never had children because of infertility. Researchers at the National Cancer Institute and several universities looked at whether infertility contributes to ovarian cancer risk.

What the researchers wanted to know: Do some causes of infertility increase the risk of ovarian cancer?

What they did: The researchers used medical records of 12,193 women who went to one of five practices for infertility advice between 1965 and 1988. They put the women's infertility diagnoses into six categories: endometriosis, not ovulating, tubal disease and pelvic adhesions, a problem with the man, cervical disorders, and uterine disorders. Then they used medical records, cancer registries, and questionnaires to find out about the women's health since the infertility visit. Infertile women were compared with each other and with the known risks for all women.

What they found: Compared with the general population, the infertile women were about twice as likely to develop ovarian cancer. Women with endometriosis were even more likely to get ovarian cancer.

What the study means to you: There appears to be some connection between infertility and ovarian cancer—especially infertility caused by endometriosis.

Caveats: Many of the women were evaluated decades ago, when doctors had fewer tools for evaluating infertility. On the other hand, the researchers point out, doctors usually evaluated women more thoroughly back then; now, they're referred for in vitro fertilization after less evaluation.

Find out more: Information about endometriosis from the National Institutes of Child Health and Human Development.

Ovarian cancer from the Mayo Clinic

Read the article: Brinton, L.A., et al. "Ovarian Cancer Risk Associated with Varying Causes of Infertility." Fertility and Sterility. August 2004, Vol. 82, No. 2, pp. 405–414.

Abstract online: www.fertstert.org