Objective: To determine the risk factors, percentage and maternal and perinatal complications of uterine rupture after previous caesarean section.
Design: Population-based registry study.
Population: Mothers with births > or =28 weeks of gestation after previous caesarean section (n = 18 794), registered in the Medical Birth Registry of Norway, from 1 January 1999 to 30 June 2005.
Methods: Associations of uterine rupture with risk factors, maternal and perinatal outcome were estimated using cross-tabulations and logistic regression.
Main outcome measure: Odds of uterine rupture.
Results: A total of 94 uterine ruptures were identified (5.0/1000 mothers). Compared with elective prelabour caesarean section, odds of rupture increased for emergency prelabour caesarean section (OR: 8.63; 95% CI: 2.6-28.0), spontaneous labour (OR: 6.65; 95% CI: 2.4-18.6) and induced labour (OR: 12.60; 95% CI: 4.4-36.4). The odds were increased for maternal age > or =40 years versus <30 years (OR: 2.48; 95% CI: 1.1-5.5), non-Western (mothers born outside Europe, North America or Australia) origin (OR: 2.87; 95% CI: 1.8-4.7) and gestational age > or =41 weeks versus 37-40 weeks (OR: 1.73; 95% CI: 1.1-2.7). Uterine rupture after trial of labour significantly increased severe postpartum haemorrhage (OR: 8.51; 95% CI: 4.6-15.1), general anaesthesia exposure (OR: 14.20; 95% CI: 9.1-22.2), hysterectomy (OR: 51.36; 95% CI: 13.6-193.4) and serious perinatal outcome (OR: 24.51 (95% CI: 11.9-51.9). Induction by prostaglandins significantly increased the odds for uterine rupture compared with spontaneous labour (OR: 2.72; 95% CI: 1.6-4.7). Prelabour ruptures occurred after latent uterine activity or abdominal pain in mothers with multiple or uncommon uterine scars.
Conclusion: Trial of labour carried greater risk and graver outcome of uterine rupture than elective repeated caesarean section, although absolute risks were low. A review of labour management and induction protocol is needed.