Relationship between duration of second stage of labour and postpartum anaemia

To assess the relationship between the duration of the second stage of labour and postpartum anaemia during vaginal birth.

An observational, analytical retrospective cohort study was performed at the "Mancha-Centro Hospital" (Spain) during the 2013-2016 period. Data were collected from 3437 women who had a vaginal birth. Postpartum anaemia was defined as a haemoglobin level below 11g/dL at 24h postpartum. A univariate analysis was used for potential risk factors and a multivariate analysis with binary logistic regression to control for possible confounding factors.

The incidence of postpartum anaemia was 42.0%. The risk of postpartum anaemia did not increase in nulliparous women whose duration of the second stage of labour exceeded 4h. Compared with multiparous women who delivered between 0 and 3h, multiparous women with a duration of the second stage of labour beyond 3h were at higher risk of postpartum anaemia (OR=2.43 [1.30-4.52]).

The duration of the second stage of labour beyond 4h is safe for postpartum anaemia in nulliparous women. However in multiparous women, monitoring should increase if the second stage of labour exceeds 3h given the increased risk of postpartum anaemia.