Operative technique at caesarean delivery and risk of complete uterine rupture in a subsequent trial of labour at term. A registry case-control study.

OBJECTIVE: To estimate the relation of single-layer closure at previous caesarean delivery, and other pre-labour and intra-partum risk factors for complete uterine rupture in trial of vaginal birth after a caesarean (TOLAC) at term.

STUDY DESIGN: Population-based case-control study. We identified all women (n = 39 742) recorded in the Danish Medical Birth Registry (DMBR) during a 12-year period (1997-2008) with a singleton pregnancy at term and TOLAC. Among these, all women with a complete uterine rupture were identified (cases). Information from the registry was validated against medical records. Controls were selected in the DMBR as the following two births with TOLAC at term and no uterine rupture. Detailed information from cases and controls was collected from manual review of medical records. Main outcome measure was complete uterine rupture during TOLAC at term.

RESULTS: Upon validation, 175 cases and 272 controls met the above criteria. After adjustment for possible confounding factors there was no association between single layer closure and uterine rupture (aOR 1.38, CI: 0.88-2.17). Significant risk factors were: Induction with an unfavourable cervix (aOR 2.10 CI: 1.19-3.71), epidural (aOR 2.17 CI 1.31-3.57), augmentation by oxytocin for more than one hour (aOR 2.03 CI: 1.20-3.44), and birth weight ≥ 4000g (aOR 2.65 CI 1.05-6.64). Previous vaginal delivery (aOR 0.41 CI: 0.25-0.68) and inter-delivery interval of more than 24 months (aOR 0.38 CI: 0.18-0.78) reduced the risk of uterine rupture.

CONCLUSION: Single-layer uterine closure did not remain significantly associated to uterine rupture during TOLAC at term after adjustment for confounding factors. Induction of labour with an unfavourable cervix, birth weight ≥ 4000g and indicators of prolonged labour were all major risk factors for uterine rupture.