The increasing role of a retained placenta in postpartum blood loss: a cohort study.

Purpose: To describe the association between quantity of blood loss, duration of the third stage of labour, retained placenta and other risk factors, and to describe the role of a retained placenta depending on the cutoff used to define postpartum haemorrhage.

Methods: Cohort study of all vaginal deliveries at two Danish maternity units between 1 January 2009 and 31 December 2013 (n = 43,357), univariate and multivariate linear regression statistical analyses.

Results: A retained placenta was shown to be a strong predictor of quantity of blood loss and duration of the third stage of labour a weak predictor of quantity of blood loss.