Obesity as an independent risk factor for group B streptococcal colonization

Objective: Approximately 25% of women are colonized with group B streptococcus (GBS). We assessed whether body mass index (BMI) is an independent risk factor for GBS colonization. Study design: We performed a retrospective cohort study using a previously collected database of women who delivered singleton gestations at term. Individual patient medical record review was undertaken to add GBS-related information to the database. Univariable logistic regression was used to assess the relationship between GBS colonization and BMI. Multivariable logistic regression was used to adjust for confounders. Results: A total of 2045 patients met enrollment criteria. The prevalence of GBS colonization was 29%. In the unadjusted analysis, there was a statistically significant increase in GBS colonization per unit increase in BMI (odds ratio [OR] 1.03, 95% confidence interval [CI] 1.01-1.04). This relationship remained significant after adjusting for confounders (race, marital status, payer, chronic hypertension, concomitant genital infections) (OR 1.01, 95% CI 1.00-1.03; p = 0.04). By BMI category, there were no differences in antibiotic susceptibilities or mode of ascertainment of GBS colonization. Conclusion: Obesity is an independent risk factor for GBS colonization; however, this association is weak.