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 < 7 at 5 min age (adjusted OR 1.13 [95% CI: 0.65-1.97]) or admission to the neonatal intensive care unit (adjusted OR 1.46 [95% CI: 0.61-3.51]) between the study groups. CONCLUSION:Women with an active second stage of labour that exceeds 60 min had an increased risk of postpartum haemorrhage > 1000 ml. We found no association between duration of active stage of labour and obstetric anal sphincter injuries or adverse neonatal outcomes.