Rupture of the scarred uterus.

OBJECTIVE: To assess the risk of uterine rupture of the scarred uterus according to mode of delivery in subsequent births recorded as spontaneous labour, labour induced by oxytocin, labour after ripening with prostaglandin E2, and planned cesarean section.

METHODS: Retrospective study of 2,128 births with a low transversal scar after a previous cesarean section. The study population was realised in a level III university hospital from 1995 to 2003. The association between mode of delivery and uterine rupture was studied in a multivariate logistic regression model, and adjusted for specific antenatal confounding factors.

RESULTS: Over 9 years, we collected 22 cases (1%), including 11 asymptomatic ruptures in a population of 2,128 scarred uteri out of 28,248 deliveries. Uterine rupture occurred at a rate of 0.3 per 100 among women with repeated cesarean delivery without labour, 1 per 100 among women with spontaneous onset of labour, 1.4 per 100 among women with oxytocin-induced labour, and 2.2 per 100 among women with prostaglandin cervical ripening. Compared to women with a planned cesarean section, women with spontaneous onset of labour were more likely to have uterine rupture (OR: 4.0; 95% CI: 0.8-42.0). A greater relative risk was observed among women with oxytocin-induced labour (OR: 4.3; 95% CI: 0.3-60.0), and particularly those with prostaglandin-induced labour (OR: 8.7; 95% CI: 1.5-97.3, p=0.01).

CONCLUSION: In women with a scarred uterus, prostaglandin E2 induction of labour is a risk factor for uterine rupture. The practice of a systematic cesarean section in cases with Bishop score<3, appropriate induction procedure, and rigorous monitoring of the labour, could make for a safer delivery.