Background A significant association was found between cesarean section (CS) and obesity at adulthood in our previous study.
Objective To assess the association between CS and obesity in schoolchildren.
Methods We carried out two birth cohorts in Brazil: in Ribeirao Preto (RP) in 1994 and in São Luís (SL) in 1997. 2846 pairs of mothers-newborns were evaluated in RP and 2542 pairs in SL. Birth length and weight and variables were collected after delivery: gender, gestational age, type of delivery, maternal schooling and smoking. In 2004/2005 a random sample were reassessed with anthropometric measurements: 790 children aged 10–11 years in RP and 673 children aged 7–9 years in SL. The outcomes were BMI in Z score and obesity (>95th percentile per age). A logistic model was used to investigate the association between CS and obesity. A multiple regression model was applied to investigate the association between CS and BMI.
Results Obesity rate was 13% in RP and 2.0% in SL. In the logistic regression, the association between CS and obesity remained significant after adjustment only in RP [1.72 (CI95% 1.01–2.92)]. The linear coefficient after adjustment the association were 0.31 (95%CI 0.11–0.51) in SL and 0.25 (95%CI 0.05–0.46) in RP.
Conclusion Cesarean section was associated to increased BMI in both cities, as previously found in adults. CS remained associated with obesity only in RP. We reinforce the previous hypothesis that intestinal flora related to type of delivery may play a role in the epidemic of obesity worldwide.