Timing of placental delivery to prevent post-partum haemorrhage: lessons learned from an abandoned randomised clinical trial.

It has been recognised that, if the length of the third stage of labour exceeds 30 min, then there is an increased risk of a post-partum haemorrhage. Recent information has suggested that 18 min is the optimal time for removal of the undelivered placenta to prevent a post-partum haemorrhage. A randomised trial comparing 20 vs. 30 min was stopped after an interim analysis because only eight of 1607 patients' placentas had not delivered by 20 min. A third stage of labour that exceeded 10 min was observed to be significantly correlated with an increased risk of post-partum haemorrhage.