Pelvic inflammatory disease, intrauterine contraception, and the conduct of epidemiologic studies.

Pelvic inflammatory disease (PID) has been described in the medical literature for more than a century as a specific entity. Neisseria gonorrhoeae, Chlamydia trachomatis, and Mycoplasma hominis, along with Bacteroides fragilis and other anaerobic bacteria, have been most frequently associated with PID. Factors affecting the occurrence of PID have been extensively studied during the past two decades and include number of sexual partners, age, race, socioeconomic status, education, and contraceptive method. As knowledge concerning factors that contribute to PID increases, epidemiologic studies addressing such issues must become increasingly sophisticated, and the literature needs to be re-evaluated in light of present knowledge. Various risk factors for PID, types of epidemiologic studies, methods for conducting such studies, and data interpretation are reviewed.