We set out to measure fetal cortisol in the human umbilical vein in relation to onset of labour, intrapartum complications and mode of delivery. Umbilical cord venous samples were obtained after delivery from 98 infants and serum total cortisol was measured. The onset of spontaneous labour, induction of labour, elective caesarean section, spontaneous vaginal delivery, emergency caesarean section in labour, instrumental delivery, the presence of meconium staining of the liquor and umbilical artery pH were examined in relation to serum fetal cortisol. Spontaneous onset of labour, mode of delivery, meconium staining of the liquor and gestational age were independent predictors of umbilical venous cortisol levels. Those infants delivered by elective caesarean section had the lowest cortisol levels, while the highest levels were recorded in those infants following instrumental delivery. Fetal cortisol is significantly elevated in association with spontaneous human parturition and is highest Its among babies born by instrumental delivery.