Peripartum Infection Associated with Vaginal Group B Streptococcal Colonization

Objective: To determine the frequency of peripartum infection in parturients colonized with group B streptococci.

Methods: We screened 915 obstetric patients for group B streptococcal colonization using selective broth media; 823 had vaginal cultures performed within 2 weeks preceding delivery and received complete follow-up. Vaginal group B streptococcal colonization and other risk factors for peripartum maternal infection were assessed using univariate and multivariate logistic modeling.

Results: Two hundred sixteen women (26%, 95% confidence interval [CI] 23-29) were colonized with group B streptococci. Chorioamnionitis or endometritis occurred in 45 of 216 colonized women (21%, 95% CI 15.6-26.4) and 72 of 607 women who were not colonized (12%, 95% CI 9-15; P < .01). When confounding variables were controlled in a multivariate analysis, the association between group B streptococcal colonization and chorioamnionitis, but not endometritis, was confirmed (odds ratio 3.6, 95% CI 2.1-6.2). The risk of chorioamnionitis increased in a stepwise fashion with light (odds ratio 1.9, 95% CI 1.0-3.7), moderate (odds ratio 2.6, 95% CI 1.3-5.2), and heavy (odds ratio 3.2, 95% CI 1.5-6.6) colonization.

Conclusion: Intrapartum vaginal colonization with group B streptococci is an important independent risk factor for chorioamnionitis.