Maternal and perinatal outcomes of prolonged second stage of labour: a historical cohort study of over 51,000 women

Abstract

Background Prolonged second stage of labour has been associated with adverse maternal and perinatal outcomes. The maximum length of the second stage from full dilatation to birth of the baby remains controversial. Our objective was to determine whether extending second stage of labour was associated with adverse maternal and perinatal outcomes. Methods A retrospective cohort study was conducted using routinely collected hospital data from 51,689 births in Aberdeen Maternity Hospital between 2000 and 2016. The hospital followed the local guidance of allowing second stage of labour to extend by an hour compared to national guidelines since 2008 (nulliparous and parous). The increasing duration of second stage of labour was the exposure. Baseline characteristics, maternal and perinatal outcomes were compared between women who had a second stage labour of (a) ≤ 3 hours and (b) > 3 hours duration for nulliparous women; and (a) ≤ 2 hours or (b)> 2 hours for parous women using univariate analysis. The following were then adjusted for: age, BMI, parity, smoking status, deprivation category, induced birth, epidural, oxytocin, gestational age, baby birthweight and mode of birth. The length of second stage was entered as a continuous variable Results Each hourly increase in the second stage of labour was associated with an increased risk of tears (aOR 1.52 95% CI 1.49-1.56), having an episiotomy (aOR 2.10 95% CI 2.06-2.14) and postpartum haemorrhage (aOR 1.55 95% CI 1.53-1.58). The rates of caesarean and forceps delivery also increased threefold when second stage duration increased (aOR 3.38 95% CI 3.26-3.50, aOR 3.18 95% CI 3.11-3.26, respectively.) No statistically significant adverse perinatal outcomes were found on multivariate analysis. Conclusions As the duration of second stage of labour increased, the risk of tears, episiotomies and PPH increases significantly. Women were 3 times more likely to have a forceps or caesarean birth. No association was found between adverse perinatal outcomes and the duration of second stage of labour in this study.