The risk of breast and gynecological cancer in women with a diagnosis of infertility: a nationwide population-based study.

Some studies have suggested that infertility is a risk factor for endometrial, ovarian and breast cancer. The study aimed to create a comprehensive picture of the association between infertility and the risk of ovarian, endometrial and breast cancer, and whether any association could be explained by ovulatory disturbances, endometriosis or nulliparity. In a population-based cohort of 2,882,847 women, cox regression analysis was used to investigate cancer incidence among infertile women. Overall, infertility was associated with a higher incidence rate of ovarian (adjusted hazard ratio [aHR] 1.53, 95% confidence interval [CI] 1.38-1.71) and endometrial cancer (aHR 1.25, 95% CI 1.11-1.40), but not of breast cancer (aHR 0.96, 95% CI 0.92-1.01). Ovarian cancer incidence was higher in women diagnosed with endometriosis, and in nulliparous women with ovulatory disturbances, compared to women with none of the diagnoses. Endometrial cancer incidence was higher in women with ovulatory disturbances, but not in women with endometriosis. These findings suggest that infertility could have long-term consequences of importance to physicians and public health workers.