Postpartum haemorrhage (heavy blood loss after childbirth) usually occurs during the third stage of labour (expulsion of the placenta and fetal membranes). It is an obstetrical emergency, and potentially fatal for the mother, that presents as severe uterine bleeding. Postpartum haemorrhage is often caused by insufficient uterine muscle tone, the presence of placental fragments, trauma to the genital tract or a coagulation disorder.

Sometimes a drug is responsible or worsens the blood loss. The main drugs implicated are heparins and other anticoagulants, especially if reintroduced shortly after a vaginal or caesarean delivery. Some serotonin reuptake inhibitors (SSRIs and SNRIs), such as venlafaxine, escitalopram and fluoxetine, which are often used throughout pregnancy for depression or anxiety, roughly double the risk of postpartum haemorrhage when used at high doses. Nonsteroidal anti-inflammatory drugs (NSAIDs) cause partial or complete loss of uterine muscle tone, making the contractions after delivery ineffective, while also inhibiting platelet aggregation. Tocolytic drugs, which inhibit uterine contractions, increase the risk of postpartum haemorrhage by relaxing the uterus after delivery. St John’s wort, antimigraine drugs prescribed for migraine attacks or cluster headaches (triptans), and some anti-infective agents and antiepileptics also carry a risk of postpartum haemorrhage.

Postpartum haemorrhage is a cause of maternal mortality. Some postpartum haemorrhages could probably be avoided by reviewing the need for any drugs the woman is taking as delivery approaches, and adapting them to the situation as necessary.

©Prescrire 1 December 2021

Source: "Serotonergic antidepressants: postpartum haemorrhage" Prescrire International 2021; 30 (232): 295-296. Subscribers only.

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