Medline ® Abstract for Reference 4

OBJECTIVE: The purpose of this study was to estimate the association between epidural dosing and the risk of uterine rupture in women who attempt vaginal birth after cesarean delivery (VBAC). STUDY DESIGN: A nested case-control study within a multicenter retrospective cohort of>25,000 women with previous cesarean delivery compared cases of uterine rupture with women without rupture (control subjects) while attempting VBAC with epidural anesthesia. Dose timing, frequency, and quantity were compared. Time-to-event analyses were performed to estimate the association between epidural dosing and risk for uterine rupture while accounting for labor duration. RESULTS: Of 804 women in the nested case-control study, 504 women (62.7%) had epidural anesthesia, with no statistical difference in epidural usage rates between cases and control subjects (70.4% vs 62.4%; P = .09). Cox-regression analysis revealed a dose-response relationship between the number of epidural doses and uterine rupture risk: 1 dose (hazard ratio, 2.8; 95% confidence interval [CI], 1.4-5.7), 2 doses (hazard ratio, 3.1; 95% CI, 2.2-6.2), 3 doses (hazard ratio, 6.7; 95% CI, 3.8-12.1),>or =4 doses (hazard ratio, 8.1; 95% CI, 5.4-18.2). CONCLUSION: Clinical suspicion for uterine rupture should be high in women who require frequent epidural dosing during a VBAC trial.