Intrapartum antibiotic use is associated with higher child body mass index (BMI) z-score at 4 years of age.

Early life antibiotic exposure may increase obesity risk. We investigated if prenatal, intrapartum, or childhood antibiotic use is associated with child zBMI score at 4 yrs of age. We included data from the Alberta Pregnancy Outcomes and Nutrition (APrON) study, a prospective cohort study, on maternal and child antibiotic exposure and clinic measures of height and weight at age 4 (n = 408). Prenatal and childhood antibiotic exposure was not associated with zBMI score. Maternal intrapartum antibiotic exposure was associated with a zBMI score increase of 0.12 (95 % CI; 0.04, 0.46) in children at 4 years of age compared to non-exposure intrapartum.