About 5 to 10 percent of the general female population is affected with endometriosis, and a higher prevalence is found among women with infertility. Although endometriosis is commonly observed in women who are infertile, it is unknown when endometriosis is the cause of infertility or an incidental discovery during the infertility examination.

"Although women with endometriosis are at greater risk for infertility compared to women without endometriosis, our study suggests that the majority of women with endometriosis do not experience infertility and the majority do become pregnant and are able to build the families that they desire." said senior study author Stacey A. Missmer, Sc.D, director of Epidemiologic Research in Reproductive Medicine at Brigham and Women's Hospital.

In this new study, researchers at Brigham and Women's Hospital collected data from 58,427 women who are participants of the Nurses' Health Study-2 to examine the relationship between endometriosis and infertility. Researchers found a higher risk of subsequent infertility in women with endometriosis, but only among women under age 35. According to the study's prospective analysis, the infertility risk posed by endometriosis is about half previous estimates and indicates a possible detection bias in earlier studies. Results are published online in Human Reproduction.

"A key step in endometriosis discovery is identifying women with endometriosis who indeed are at higher risk of infertility so that treatments can be targeted directly to the biology causing infertility and identifying these women as early as possible so they can access fertility treatment," Missmer said.

A prospective cohort study of endometriosis and subsequent risk of infertility. J. Prescott, L.V. Farland, D.K. Tobias, A.J. Gaskins, D. Spiegelman, J.E. Chavarro, J.W. Rich-Edwards, R.L. Barbieri and S.A. Missmer. Human Reproduction. DOI:10.1093/humrep/dew085. Published online May 1, 2016.