['To compare the need for positive pressure ventilation (PPV) by bag and mask and by bag and endotracheal tube in newly born term infants with vertex presentation delivered by non-urgent caesarean section under regional anaesthesia or non-instrumental vaginal delivery.', 'Cross-sectional study.', '35 public hospitals in 20 Brazilian state capitals.', '6929 inborn infants without congenital anomalies, with gestational ages from 37(0/7) to 41(6/7) weeks with vertex presentation, born between 1 and 30 September 2003.', 'Non-urgent caesarean versus non-instrumental vaginal delivery. Non-urgent caesarean was defined as delivery occurring in the absence of prolapsed cord, third trimester haemorrhage, failure of labour induction, fetal distress or non-clear amniotic fluid.', 'PPV with bag and mask and with bag and endotracheal tube. Both outcomes were adjusted for potential confounding variables by logistic regression analysis.', '2087 infants were born by non-urgent caesarean and 4842 by non-instrumental vaginal delivery. Non-urgent caesarean delivery under regional anaesthesia compared to vaginal delivery under local or no anaesthesia increased the risk of bag and mask ventilation (OR 1.42, 95% CI 1.07 to 1.89) adjusted for number of gestations, maternal hypertension and birth weight. Ventilation with bag and endotracheal tube was associated only with low birth weight, adjusted for delivery mode and twin gestation.'] Does non-urgent caesarean delivery increase the need for ventilation at birth in term newborn infants?