Objective To examine the association between decision to delivery interval and maternal and baby outcomes. Design National cross sectional survey. Setting Maternity units in England and Wales. Subjects reviewed 17 780 singleton births (99% of all births) delivered by emergency caesarean section in England and Wales between 1 May 2000 and 31 July 2000. Main outcome measures Association between decision to delivery interval and baby outcomes (Apgar scores of <7 and <4 at five minutes and stillbirth) and maternal outcomes (requirement for special care additional to routine care after caesarean section and where care was provided). Results Compared with babies delivered within 15 minutes, there was no difference in maternal or baby outcome for decision to delivery interval between 16 and 75 minutes. After 75 minutes, however, there was a significantly higher odds of a five minute Apgar score of <7 (odds ratio 1.7, 95% confidence interval 1.2 to 2.4), and 50% increase in odds of special care additional to routine care for mothers. Conclusion A decision to delivery interval of 30 minutes is not an absolute threshold for influencing baby outcome. Decision to delivery intervals of more than 75 minutes are associated with poorer maternal and baby outcomes and should be avoided.