Risk factors for uterine rupture among women who attempt a vaginal birth after a previous cesarean: a case-control study.

OBJECTIVE: To identify risk factors associated with uterine rupture among term pregnancies attempting a vaginal birth after a previous cesarean. STUDY DESIGN: A case-control study was done of 348 uterine ruptures in Massachusetts between 1991 and 1998, initially screened by ICD-9 code and confirmed by medical record review, with 424 control women with a trial of labor randomly selected proportional to cases on year of delivery. Multivariable regression was used to estimate odds ratios and 95% confidence intervals. RESULTS: Successful previous vaginal birth decreased risk for uterine rupture, and gestation > 40 weeks and macrosomia increased risk. Oxytocin for induction increased risk, with a slightly lower effect when used for augmentation. Prostaglandin use in conjunction with oxytocin did not have an additive uterine rupture risk. Women using epidural analgesia have an increased uterine rupture risk. CONCLUSION: Certain labor management practices increase the risk for uterine rupture 2-3 times, although the absolute increase is small from a baseline uterine rupture rate of 0.5% to 1.0-1.5%. The association between epidural analgesia and uterine rupture deserves further study.