Associations of prenatal and childhood antibiotic use with child body mass index at age 3 years

Objective Early‐life antibiotic exposure, whether through prenatal or childhood antibiotic use, may contribute to increased child body mass. Associations of prenatal and childhood antibiotic use with body mass index z ‐score (BMIz) were evaluated at age 3 years. Methods Electronic health records were utilized from 8,793 mothers and singleton children delivered at Geisinger Clinic in Pennsylvania between 2006 and 2012. Antibiotic orders were ascertained for mothers during pregnancy and for children through their age‐3 BMI measurement. Linear mixed‐effects regression models evaluated associations of prenatal and childhood antibiotic use with child BMIz. Results Prenatal antibiotic orders were not associated with child BMIz. Children in the three largest categories of lifetime antibiotic orders had higher BMIz compared with children with no orders; associations persisted when controlling for prenatal antibiotics ( β [95% confidence interval]) (4‐5 child orders: 0.090 [0.011 to 0.170]; 6 to 8: 0.113 [0.029 to 0.197]; ≥9: 0.175 [0.088 to 0.263]; trend P value <0.001). Two or more first‐year orders were also associated with BMIz (1: 0.021 [−0.038 to 0.081]; 2: 0.088 [0.017 to 0.160]; ≥3: 0.104 [0.038 to 0.170]; trend P value < 0.001). Conclusions Associations of early‐life and lifetime childhood antibiotic use with increased child BMI highlight antibiotic exposure as a modifiable factor for reducing population‐level excess weight.