An epidemiologic case-control study of ovarian cancer and reproductive factors.

A population-based case-control study was conducted with 403 white, ovarian cancer patients, 20-79 years of age, who were diagnosed from October 1977 through February 1980 in 11 New York State counties. The study also included 806 controls who were matched to the cases by age, race, and county of residence. The contraceptive and reproductive patterns observed in this study suggest that infertility plays an important role in determining the relationship between reduced parity and gravidity and increased ovarian cancer risk. Ovarian cancer patients were less likely than controls to have ever used nonpermanent birth control methods (relative risk = 0.63, 95% confidence interval = 0.45-0.89), and they tended to practice contraception less often. A direct graded-response relationship was observed between ovarian cancer risk and the number of contraceptive-free years of marriage (chi 2 Linear trend = 5.911, p = 0.02). An inverse graded-response relationship was observed between gravidity and risk. This relationship persisted even after contraception was taken into account (chi 2 Linear trend = 13.002, p = 0.0003). Ovarian cancer risk was not found to be associated with an excess in reported fetal loss.