Oral contraceptives and pelvic inflammatory disease.

To study the association of the use of oral contraceptives and pelvic inflammatory disease (PID), we analyzed data from a large multicenter case-control study of contraceptive use and serious gynecologic disorders. The analysis included data from interviews of 648 women hospitalized with an initial episode of PID and 2,516 hospitalized control subjects. The risk of PID for women using oral contraceptives in the 3 months prior to interview was 0.5 (95% confidence limits, 0.4 to 0.6) relative to women using no contraceptive method during this period. This association was not explained by differences between case subjects and control subjects in demographic variables, level of sexual activity, or medical history. The protective effect of current oral contraceptive use against PID was restricted to women using oral contraceptives for more than 12 months; past use of oral contraceptives did not exert a protective effect against PID. Annually, an estimated 50,000 initial cases of PID are prevented by oral contraceptive use; 12,500 hospitalizations are also averted by oral contraceptive use. Consequently, protection against PID is one of the most important noncontraceptive benefits of oral contraception.