Caesarean section and obesity in young adult offspring: Update of a systematic review with meta-analysis.

As compared with vaginal delivery (VD), caesarean section (CS) birth could be associated with increased risk of obesity in young adult offspring. We aimed to evaluate this association by updating data from a systematic review with meta-analysis of observational studies. From 3774 records identified in PubMed and Embase, we retained six studies and added five studies from the last systematic review, for a total of 11 studies. Crude estimates of the association were retrieved from nine cohort studies (n = 143,869), and maximally adjusted estimates were retrieved from eight cohort studies. Young adults born by CS had higher risk of obesity (body mass index [BMI] ≥ 30 kg/m2 ) than young adults born by VD, corresponding to a crude pooled risk ratio (RR) of 1.30 [95% confidence interval (CI) 1.13 to 1.50] and a maximally adjusted pooled RR of 1.22 [95% CI 1.02 to 1.46]. In a sensitivity analysis pooling, five studies that included maternal prepregnancy BMI, a major potential confounding factor, in the set of controlled covariates, the RR was 1.08 [95% CI 0.92 to 1.27]. We concluded that the association between CS and obesity in young adulthood was mostly explained by confounding from maternal prepregnancy BMI.