Objective To investigate the effect of feeding during labour on obstetric and neonatal outcomes. Design Prospective randomised controlled trial. Setting Birth centre in London teaching hospital. Participants 2426 nulliparous, non-diabetic women at term, with a singleton cephalic presenting fetus and in labour with a cervical dilatation of less than 6 cm. Intervention Consumption of a light diet or water during labour. Main outcome measures The primary outcome measure was spontaneous vaginal delivery rate. Other outcomes measured included duration of labour, need for augmentation of labour, instrumental and caesarean delivery rates, incidence of vomiting, and neonatal outcome. Results The spontaneous vaginal delivery rate was the same in both groups (44%; relative risk 0.99, 95% confidence interval 0.90 to 1.08). No clinically important differences were found in the duration of labour (geometric mean: eating, 597 min v water, 612 min; ratio of geometric means 0.98, 95% confidence interval 0.93 to 1.03), the caesarean delivery rate (30% v 30%; relative risk 0.99, 0.87 to 1.12), or the incidence of vomiting (35% v 34%; relative risk 1.05, 0.9 to 1.2). Neonatal outcomes were also similar.