The role of infection in the etiology of preterm birth.

The hypothesis that infection induces or is a precursor to preterm birth or premature rupture of the membranes was examined in a prospective study of 193 randomly selected pregnant women. We investigated the prognostic significance of factors that suggest infection of the uterine cavity before pregnancy, such as a history of pelvic inflammatory disease, a history of intrauterine contraceptive device (IUD) use, multiple sex partners, and the presence of antisperm antibodies, in relation to premature rupture of the membranes and preterm birth. Sexual activity, a potential vehicle for bacterial exchange, was also charted throughout pregnancy via monthly interviews. We performed immunologic tests on each patient and obtained cultures of the cervix for aerobic and anaerobic bacteria and chlamydia at the first visit, occurring at six to 14 weeks' gestation, and again at 36 weeks. The results suggest that infection may indeed play a causative role in premature rupture of the membranes or preterm birth. A strong correlation was found between preterm birth and both a history of pelvic inflammatory disease (P = .004) and a history of IUD use (P = .0015). Amnionitis was associated with the presence of immunoglobulin G (IgG) antisperm antibodies (P = .02), as well as with a history of pelvic inflammatory disease (P = .0006). There was also a correlation between premature rupture of the membranes and a history of multiple sex partners (P = .02). This collective evidence implicates preexisting infection of the uterine cavity as a predisposing factor in premature rupture of the membranes, preterm delivery, and amnionitis.