Oral contraceptives, other methods of contraception, and risk reduction for ovarian cancer.

Oral contraceptives reduce the risk of ovarian cancer, but the impact of other methods of contraception has not been fully explored. This population-based, case-control study involved women 20-69 years of age who had ever had intercourse. We compared cases with a recent diagnosis of ovarian cancer (N = 727) with community controls (N = 1,360). All methods of contraception evaluated were associated with a reduced risk for ovarian cancer. After adjustment for age, race, pregnancies, and family history of ovarian cancer, the odds ratios for ever-use of each method as compared with never-use were: oral contraceptives for contraception, 0.6 (95% confidence interval = 0.5-0.8); intrauterine device, 0.8 (95% confidence interval = 0.6-1.0); barrier methods, 0.8 (95% confidence interval = 0.6-0.9); tubal ligation, 0.5 (95% confidence interval 0.4-0.7); and vasectomy, 0.8 (95% confidence interval = 0.6-1.1). Nulligravid women were not protected by any of these contraceptive methods. Multigravid women, however, were protected by all methods. We conclude that various methods of contraception reduce ovarian cancer risk. This effect does not appear to result from contraceptive use being a nonspecific marker of fertility. The results imply mechanisms other than hormonal or ovulatory by which ovarian cancer risk is reduced.