Infertility and Risk of Ovarian Cancer in the Women’s Health Initiative
There is a consistent relationship with greater ovulation frequency and increased risk of ovarian cancer. However, prior research on infertility, which may be associated with ovulation frequency through multiple mechanisms, and ovarian cancer has yielded conflicting results, possibly due to prior research conflating fertility treatment with infertility and restricting follow-up to premenopausal cases. Our objective was to determine the association between infertility and risk of postmenopausal ovarian cancer, overall and by histotype, in a population that had not received treatment with IVF. We utilized data from the Women's Health Initiative (n = 112,925 postmenopausal participants) with over 25 years of follow-up. At baseline, participants were asked whether they had ever tried to become pregnant for more than one year without becoming pregnant and whether a reason was found. Cox proportional hazards models were used to calculate hazard ratios (HRs) of incident adjudicated ovarian cancer comparing participants with a history of infertility to fertile participants overall and by histotype. 17% of participants reported a history of infertility at baseline and 1,109 ovarian cancer cases were diagnosed during follow-up. No statistically significant association was observed between infertility and risk of any ovarian cancer (HR: 1.09, 95% CI 0.92-1.29), but those reporting infertility had a 90% higher risk of endometrioid and clear cell ovarian cancers (HR: 1.90 95% CI 1.09-3.34) compared to fertile participants. The reported reason(s) for infertility had no discernable impact on these associations. Infertility may be associated with clear cell and endometrioid ovarian cancer but not other ovarian tumor histotypes.