Uterine atony prophylaxis with carbetocin versus oxytocin and the risk of major haemorrhage during caesarean section: A retrospective cohort study.

Carbetocin and oxytocin are commonly recommended agents for active management of the third stage of labour. Evidence is inconclusive whether either one more effectively reduces the occurrence of important postpartum haemorrhage outcomes at caesarean section. We examined whether carbetocin is associated with a lower risk of severe postpartum haemorrhage (blood loss ≥ 1000 ml) in comparison with oxytocin for the third stage of labour in women undergoing caesarean section. This was a retrospective cohort study among women undergoing scheduled or intrapartum caesarean section between 1 January 2010 and 2 July 2015 who received carbetocin or oxytocin for the third stage of labour. The primary outcome was severe postpartum haemorrhage. Secondary outcomes included blood transfusion, interventions, third stage complications and estimated blood loss. Outcomes were examined overall and by timing of birth, scheduled versus intrapartum, using propensity score-matched analysis. Among 21,027 eligible participants, 10,564 women who received carbetocin and 3836 women who received oxytocin at caesarean section were included in the analysis. Carbetocin was associated with a lower risk of severe postpartum haemorrhage overall (2.1% versus 3.3%; odds ratio, 0.62; 95% confidence interval 0.48 to 0.79; P < 0.001). This reduction was apparent irrespective of timing of birth. Secondary outcomes also favoured carbetocin over oxytocin. In this retrospective cohort study, the risk of severe postpartum haemorrhage associated with carbetocin was lower than that associated with oxytocin in women undergoing caesarean section. Randomised clinical trials are needed to further investigate these findings.