Risk factors for uterine rupture during a vaginal birth after one previous caesarean section: a case-control study.

Objective: To study risk factors for uterine rupture (UR) in women with one previous caesarean section (CS) undergoing a vaginal birth after CS (VBAC).
Study Design: A nested case-control study was conducted. Baseline characteristics, general obstetric history, details of the previous CS, current delivery and maternal and neonatal outcome were analysed for 41 cases with a UR and 157 controls (no rupture). Data were extracted from 21 Dutch hospitals.
Results: Labour induction was more common in cases than in controls (51% vs. 25% respectively, P=0.001), and in case of induction therapy especially the use of prostaglandins (PGE2) was more frequent in the case group (86% vs. 46%, P=0.014 for cases and controls respectively). Patients with UR had a significantly lower Bishop score (median: 2.0 vs. 4.0, P=0.005) and received more augmentation of labour compared to controls (36% vs. 18%, P=0.010). In the multivariate analysis induction with PGE2 and oxytocin, induction with PGE2 alone, and augmentation of labour were independent variables affecting the occurrence of UR (respectively OR 13.0, CI 2.3-74.2; OR 4.6, CI 1.9-11.3 and OR 2.7, CI 1.2-6.3). Forty-four percent of the ruptures can be explained by induction of labour with prostaglandins+/-oxytocin.
Conclusion: Having studied baseline characteristics, general obstetric history, details of the previous CS and of the current delivery, we show that no factors other than the use of PGE2 (+/-oxytocin) in response to a low Bishop score, and augmentation of labour with oxytocin are associated with an increased risk for UR in women undergoing VBAC after one previous CS.
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