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.