Associations between duration of active second stage of labour and adverse maternal and neonatal outcomes: A cohort study of nulliparous women with spontaneous onset of labour

Objective To investigate associations between the duration of the active second stage of labour and adverse maternal and neonatal outcomes. Method This cohort study is based on data from a cluster randomised controlled trial (RCT) undertaken at 14 Norwegian birth clinics in Norway from 2014 to 2017. The final sample involved 6804 nulliparous women with a singleton fetus, cephalic presentation, spontaneous onset of labour at term, vaginal delivered and with an active second stage of labour. The women were grouped to active second stage of labour ≤ 60 min and active second stage of labour > 60 min. Binary logistic regression was used to estimate crude and adjusted odds ratios (ORs) of the maternal and neonatal outcomes with an associated 95% confidence intervals (CIs), comparing women in the two groups. Results There was an increased risk of postpartum haemorrhage > 1000 ml with an adjusted OR 1.31 (95% CI: 1.01–1.69) when the active second stage of labour exceeded 60 min. There was no significant difference in the risk of obstetric anal sphincter injuries (adjusted OR 0.93 [95% CI: 0.65–1.39]), Apgar scores 1000 ml. We found no association between duration of active stage of labour and obstetric anal sphincter injuries or adverse neonatal outcomes.