Update on the use of uterotonic agents

Postpartum haemorrhage (PPH) is defined by the WHO as a blood loss >500mL after vaginal delivery or >1000mL after caesarean section during the first 24hours post-delivery. Although the incidence of maternal mortality caused by PPH has decreased, it continues to be the major cause of maternal mortality due to obstetric haemorrhage. Furthermore, the incidence of uterine atony, which is the most prevalent cause of PPH, is still increasing in both vaginal delivery and caesarean section. Although PPH occurs in more than two thirds of patients without any identifiable risk factor, a prolonged third stage of labour is the main risk factor. Active management of the third stage of labour has been postulated to reduce the risk of bleeding in this period. It includes the administration of uterotonic agents after the birth of the baby. Uterotonic agents are defined as drugs that produce adequate uterine contraction. These drugs can be used as prophylactic therapy or treatment. The prophylactic use of uterotonic agents has been reported to be associated with a shorter third stage of labour, less risk of PPH and less need of additional uterotonic agents. There are currently four drugs or groups of drugs with uterotonic action: oxytocin, carbetocin, ergot derivatives and prostaglandins. The literature on this subject is extensive, heterogeneous and sometimes discordant. Oxytocin is still the first-line uterotonic drug for prophylaxis and treatment of uterine atony. There is a common trend to use high doses of uterotonics for fear of inadequate uterine contraction, but the current literature recommends its reduction. Methylergonovine continues being the second-line uterotonic agent in the prophylaxis and treatment of PPH, because of its side effects. Despite carboprost (PGF2α) side effects, it is still the first-line prostaglandin for PPH treatment. Misoprostol may be an alternative to oxytocin when it is not available, although it needs further studies to support this. Finally, the prophylactic use of carbetocin should be individualised.