Objective To assess if delivery mode and duration of labour in a first labour of spontaneous onset is associated with gestational length, delivery mode 3and neonatal outcome in the subsequent pregnancy. Study Design Retrospective analysis of prospectively collected data. Setting 15 Maternity units in North West London (1988 to 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 spontaneous or instrumental birth in pregnancy 1 the median duration was similar, with preterm delivery rates of 4.5% and 3.9%. 56.2% of women with a CS in pregnancy 1 had a repeat CS and 12.5% of their babies were admitted to neonatal unit, compared with 5.3% of women with vaginal birth. Longer labours were associated with shorter gestations in pregnancy 2. Conclusions Compared to 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.