Vaginal Bacteroides Species Are Associated with an Increased Rate of Preterm Delivery among Women in Preterm Labor

The relationship of high concentrations of vaginal microorganisms with an increased rate of preterm delivery (⩽34 weeks) among women in preterm labor was evaluated. Quantitative vaginal cultures were obtained from 211 women in preterm labor between gestational ages of 22 and 34 completed weeks. Preterm delivery occurred in 139 (66%). The rate of preterm delivery was determined by Cox proportional hazards models. Women with >107 cfu/ml of vaginal fluid of facultative lactobacilli had a 40% decreased rate of preterm delivery (rate ratio [RR] = 0.6, 95% confidence interval (CI) = 0.4–0.9). An increased rate of preterm delivery occurred among women with Bacteroides bivius at concentrations of >104 cfu/ml (RR = 2.0, 95% CI = 1.4–2.9) and Bacteroides fragilis (RR = 1.7, 95% CI = 1.0–2.8). Other microorganisms, including Gardernella vaginalis, the genital mycoplasmas, group B streptococci, Escherichia coli, and Peptostreptococcus species, were not associated with an increased rate of preterm delivery for women in pre term labor.