Early-life antibiotic exposure and the risk of overweight and obesity in children

BACKGROUND: Early antibiotic exposure has been associated with increased weight gain in children. Evidence associating the timing of antibiotic exposure to overweight and obesity is limited. METHODS: This population-based cohort study included 33,095 vaginally delivered children with 595,213 growth measurements linked to medical records and national registers. Exposures included antibiotic exposure during the year before pregnancy, during pregnancy, in the perinatal period, and within the first 24 months of life. The primary outcomes were zBMI at 24 months of age and the cumulative incidence of overweight and obesity up to 12 years of age. RESULTS: Antibiotic exposure before or at birth was not associated with childhood overweight or obesity. Exposure during the first 24 months of life was linked to a higher zBMI at two years of age. Long-term analysis revealed an adjusted hazard ratio of 1.09 (95% CI 1.04-1.13) for overweight and 1.20 (95% CI, 1.10-1.31) for obesity. CONCLUSION: Antibiotic exposure during the first two years of life was associated with childhood overweight and obesity. No similar associations were observed for exposure before or at birth. Interventions aiming to reduce obesity-related effects should focus on minimizing early-life antibiotic use within the first two years of life. IMPACT: Early-life antibiotics have been associated with childhood overweight and obesity. We investigated how the timing of early-life antibiotic exposure is associated with childhood overweight and obesity. Antibiotic exposure in the first two years of life was associated with overweight and obesity. No similar associations were found with antibiotic exposure before pregnancy, during pregnancy, or in the perinatal period. Interventions aiming to reduce obesity-associated effects should focus on the first two years of life.