Relationship between maternal group B streptococcal colonization and pregnancy outcome

To examine the association of maternal colonization with group B streptococcus (GBS) with preterm labor and premature rupture of the membranes (PROM).

Vaginal cultures were conducted in 615 women at 22-26 weeks' gestation and again on admission for term delivery, preterm labor, or PROM. Antibiotics were not given antenatally based on a GBS-positive culture result. Fisher exact test and maximum likelihood analysis were used for statistical analysis.

The rates of preterm labor and PROM were not significantly different between GBS-positive and GBS-negative women in both the antenatal screening and the screening on admission. According to maximum-likelihood analyses, the known risk factors for preterm labor and PROM collectively were important risk factors for preterm labor (odds ratio: 6.48), but GBS colonization during pregnancy was not a risk factor for preterm labor or PROM. In the antenatal screening, the proportion of subjects with lactobacilli-reduced vaginal flora was significantly higher in GBS-positive women (14.3%; ten of 70) than in GBS-negative women (6.4%; 35 of 545) (P = 0.26). Bacteria associated with bacterial vaginosis (Gardnerella vaginalis and anaerobes) were isolated in only 3.7% (23 of 615) of all subjects.

Vaginal colonization with GBS was not associated with preterm labor and PROM in an obstetric population with a low incidence of bacterial vaginosis-associated bacteria, despite the presence of lactobacilli-reduced flora in GBS-positive women.