Context

Since 2008, several observational studies have reported an association between caesarean section (CS) and offspring obesity. The underlying biological mechanism hypothesised to explain this association is that children born via CS lack exposure to the maternal vaginal flora, resulting in colonisation of the gut with flora that increase energy harvesting from food, thereby contributing to the development of obesity. Maternal pre-pregnancy weight confounds this association, as obesity in the mother is associated with CS and offspring obesity. Not all previous studies were able to adjust for maternal pre-pregnancy weight, but a recent systematic review showed that in studies that were able to adjust for this confounder, there remained a statistically significant …