Prolonged second stage of labour in primiparas and perinatal outcomes

To evaluate mode of delivery and adverse maternal and neonatal outcomes associated with a prolonged second stage of labour >3 h with an epidural or >2 h without, in primiparous term births of live singleton vertex fetuses.

A retrospective cohort study (2005-2022) of all primiparous term births of live singleton vertex fetuses from a tertiary medical center. Parturients with prolonged second stage of labour were compared to those with a second stage within normal limits. Primary outcome was mode of delivery. Secondary outcomes included maternal and neonatal adverse outcomes. Statistical analyses included comparisons and multivariate modelling, p < 0.05.

Of 55,309 primiparous term births of live singleton vertex fetuses, prolonged second stage of labour occurred in 13.1 % of primiparas (85 % with and 15 % without an epidural). Caesarean delivery rates were higher in the prolonged second stage of labour group 8.5 % vs. 0.8 %, p < 0.0001, spontaneous vaginal delivery rates were lower in prolonged second stage of labour (48.4 % vs. 85.6 %, p < 0.0001), and instrumental delivery rates were higher (43.1 % vs. 13.6 % p < 0.0001). Prolonged second stage of labour was significantly associated with postpartum haemorrhage (1.1 % vs. 0.8 %), third- or fourth-degree perineal lacerations (1.8 % vs. 1.0 %), shoulder dystocia (0.5 % vs. 0.1 %), neonatal intensive care unit admissions > 72 h (3.6 % vs. 2.4 %), clavicular fractures (0.7 % vs. 0.4 %), and 5-minute Apgar scores < 7 (1.3 % vs. 0.7 %) (p < 0.0001). Prolonged second stage of labour was independently associated with higher risk for composite adverse maternal and neonatal outcomes, respectively (27.9 % vs. 13.6 %, OR 2.2 [2.1-2.4]) (16.8 % vs. 11 %, p < 0.0001, OR 1.1 [1.03-1.2]).

We found an increased risk of adverse maternal and neonatal outcomes in primiparas with a prolonged second stage of labour. Extending this time may lead to further aggravation of these outcomes.