Exposure to group B Streptococcal antibiotic prophylaxis and early childhood body mass index in a vaginal birth cohort.

Perinatal antibiotic exposure may be associated with changes in both early infancy gut microbiota and later childhood obesity. Our objective was to evaluate if group B Streptococcus (GBS) antibiotic prophylaxis is associated with higher body mass index (BMI) in early childhood. This is a retrospective cohort study of mother/child dyads in a single hospital system over a 6-year period. All women with term, singleton, vertex, vaginal deliveries who received no antibiotics or received antibiotics only for GBS prophylaxis and whose children had BMIs available at 2-5 years of age were included. Children were divided into three groups for comparison: children born to GBS positive mothers that received antibiotics solely for GBS prophylaxis, children born to GBS negative women that received no antibiotics (healthy controls), and children born to GBS positive mothers who received no antibiotics. The primary outcome was the earliest available child BMI -score at 2-5 years of age. Multivariable linear regression was used to estimate differences in child BMI -scores between groups, adjusted for maternal BMI, age, race, parity, tobacco use, and child birthweight. Of 4825 women, 786 (16.3%) were GBS positive and received prophylactic antibiotics, 3916 (81.2%) were GBS negative and received no antibiotics, and 123 (2.5%) were GBS positive but received no antibiotics. Childhood BMI -scores were similar between children exposed to intrapartum GBS prophylaxis and healthy controls who were unexposed in both unadjusted (mean (SE), 0.04 (0.04) versus -0.3 (0.02),  = .11) and adjusted (0.01 (0.05) versus -0.04 (0.03),  = .3) models. Exposure to intrapartum antibiotic prophylaxis for GBS was not associated with higher early childhood BMI -scores compared to healthy controls.