This cohort study from Denmark aimed to identify risk factors for severe postpartum haemorrhage (PPH - loss of ≥1000 ml). Women included in the study gave birth to a single baby vaginally at term from 1^st January 2004 to 31^st December, 2012.

Of the 31,837 births, 1,832 women (5.7%) experienced severe PPH. Maternal age, smoking during pregnancy, and pre-pregnancy body mass index did not increase the risk of severe PPH. However, nulliparous and multiparous women who had previously given birth by caesarean had an increased risk of severe PPH. Other risk factors included gestational age greater than 40 weeks, induction and/or augmentation of labour, abnormal fetal position, instrumental birth, and birthweight  of more than 4000g. The combination of induction and augmentation of labour doubled the risk of severe PPH. Vaginal tears of more than 3 cm were associated with the highest risk of severe PPH.

The authors conclude that obstetric interventions, high birthweight and extensive vaginal tears increase the risk of severe PPH, and that rigorous indications for obstetric interventions are required along with appropriate management of genital tract tears to reduce the risk.

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Read more: Graugaard, H., Maimburg, R. (2021) Is the increase in postpartum hemorrhage after vaginal birth because of altered clinical practice?: A register‐based cohort study. Birth. doi.org/10.1111/birt.12543