Pregnancy recency and risk of ovarian cancer

Objective: A recent analysis suggested that ovarian cancer risk increased w ith time since last birth, possibly because of some aspect of pregnancy tha t affects the clearance of cells that have undergone malignant transformati on. We analyzed data from four case-control studies pertaining to ovarian c ancer risk in relation to age at first pregnancy, age at last pregnancy, an d years since last pregnancy: 628 cases and 3432 neighborhood or population controls, ages 18-79, were included. Methods: We used logistic regression to analyze associations between ovaria n cancer risk, controlling for study, age (at diagnosis or corresponding re ference age for controls), race, parity, oral contraceptive use, tubal liga tion, family history of ovarian or breast cancer, and excluding women with a history of infertility. Results: An early age at first pregnancy was associated with an increased r isk of ovarian cancer (odds ratio 1.4, 95% confidence interval (1.1-1.8) fo r ages less than or equal to 19 compared to greater than or equal to 25). Y ears since last pregnancy was also associated with increased ovarian cancer risk, with odds ratios of 1.4, 1.4, 1.8, and 2.1 for 10-14, 15-19, 20-24, and greater than or equal to 25 years compared to 0-9 years (trend test p = 0.004), respectively. Conclusion: These observations support the results from the previous study, and raise additional questions about the role of pregnancy in the etiology of ovarian cancer.