The effect of mode of delivery and duration of labour on subsequent pregnancy outcomes: a retrospective cohort study

OBJECTIVE: To assess whether delivery mode and duration of labour in a first labour of spontaneous onset is associated with gestational length, delivery mode and neonatal outcome in the subsequent pregnancy. STUDY DESIGN: Retrospective analysis of prospectively collected data. SETTING: 15 Maternity units in North West London (1988-2000). POPULATION: 30 840 women with spontaneous onset of labour in pregnancy 1 and a subsequent birth reported in the same database. METHODS: Assessment of outcomes by mode of delivery in pregnancy 1, restricting the analysis to the difference in the gestational length between pregnancy 1 and 2. MAIN OUTCOME MEASURES: Gestational length, mode of delivery and neonatal unit admission in pregnancy 2. RESULTS: Caesarean section (CS) in the first or second stage of labour in pregnancy 1 was associated with pregnancy 2 being a median of 5 and 8 days shorter and a preterm birth rate of 6.0% and 10.1%, respectively, whereas following a normal or instrumental vaginal birth in pregnancy 1, the median duration was similar, with preterm delivery rates of 4.5% and 3.9%. In all, 56.2% of women with a CS in pregnancy 1 had a repeat CS and 12.5% of their babies were admitted to a neonatal unit, compared with 5.3% of women with vaginal birth. Longer labours were associated with shorter gestations in pregnancy 2. CONCLUSIONS: Compared with vaginal birth, an emergency CS in the first-term pregnancy is associated with a shorter gestational length, increased rate of repeat CS and increased risk of NNU admission in the next pregnancy. TWEETABLE ABSTRACT: An emergency caesarean section in the first-term pregnancy affects the duration and outcome of the next pregnancy.