Association between intrauterine device and pelvic inflammatory disease.

The Women's Health Study, a concurrent case-control study at 16 hospitals in 9 cities across the United States, examined the relationship between use of an intrauterine contraceptive device (IUD) and pelvic inflammatory disease (PID) severe enough to require hospitalization. After final classification, 1447 patients were eligible as PID subjects and 3453 patients were eligible as controls. For all current IUD users, the estimated relative risk of hospitalization with the diagnosis of PID was 1.6. However, the relative risk was about twofold when only individuals experiencing their first episode of the disorder were considered. The study also demonstrated an increased association for women aged 25 years or less and for nonblack women. Recent insertion or reinsertion of an IUD was associated with increased risk for PID, but total duration of use was not. Furthermore, the effect of IUD use on the development of PID persisted for several months after the IUD had been removed. The study also confirmed previous findings that the type of device does not markedly influence risk, and that the relative risk of PID is higher when IUD use is compared with use of other contraceptives or use of no contraceptives. Finally, the study suggests that users of nonpermanent forms of contraception other than the IUD have some form of protection against the development of PID.