The long-term effects of birth by caesarean section: the case for a randomised controlled trial.

Birth by caesarean section is rising rapidly around the world and is associated with a range of adverse short and long-term outcomes in offspring. The latter include features of the metabolic syndrome, type-1 diabetes, and asthma. Though there are several plausible candidate biological mechanisms, evidence of a causal relationship between mode of delivery and long-term outcomes remains lacking. Here we review the evidence to date, and examine ways in which future studies might advance understanding. We conclude that a randomised controlled trial of mode of delivery for the healthy term, cephalic pregnancy, is neither unethical nor unfeasible and should be seriously considered as the optimum means of addressing a question of great relevance to public health.