Caesarean section and childhood obesity at age 3 years: a large-scale birth cohort study— the Japan Environment and Children’s Study

Abstract

Background Caesarean section (CS) birth is widely reported to be a risk factor for childhood obesity, but it is unclear whether this association also applies in the Japanese population. Objectives To assess the impact of CS birth on obesity at 3 years of age in Japanese children. Methods We obtained data from the Japan Environment and Children’s Study, a large-scale birth cohort study that includes 103,057 pregnancies, on delivery mode and covariates. Obesity was determined by body mass index measured at 3 years of age. Adjusted odds ratios were estimated using multivariable logistic regression. Results From 60,417 mother–toddler pairs analysed, 11,125 toddlers (18.4%) had a CS birth and 12,713 toddlers (21.0%) were obese. The adjusted odds ratio for obesity at 3 years of age when born by CS compared with vaginal delivery was 1.13 (95% confidence interval [CI] 1.07–1.19). This increased odds ratio was significant for girls (1.20, 95% CI 1.11–1.30) but not boys (1.07, 95% CI 0.996–1.15). Conclusions CS birth modestly increases the risk of obesity at 3 years of age in Japanese children, especially girls.