Vaginal birth after cesarean and uterine rupture rates in California

Objective: To describe attempted and successful vaginal birth after cesarea n (VBAC) rates and uterine rupture rates for women with and without prior c esareans, and compare delivery outcomes in hospitals with different attempt ed VBAC rates. Methods: We used California hospital discharge summary data for 1995 to cal culate attempted and successful VBAC rates and uterine rupture rates. We us ed multivariate logistic regression models to evaluate and adjust for age, ethnicity, and payment source. We report the relative risk (RR), attributab le fraction, and 95% confidence intervals (CIs) for uterine rupture. Results: There were 536,785 delivery discharges during 1995. The cesarean r ate was 20.8%, and 12.5% of women had histories of cesareans. Of women with histories of cesareans, 61.4% attempted VBAC and 34.8% were successful. Th ere were 392 uterine ruptures (0.07%). Women with prior cesareans were 16.9 8 (95% CI 13.51, 21.43) times more likely to experience uterine rupture, at tributable fraction 66% (95% CI 60%, 73%). Among women with prior cesareans , those who attempted VBAC were 1.88 (95% CI 1.45, 2.44) times as likely to have uterine rupture, attributable fraction 34% (95% CI 21%, 46%). Women w ho delivered in hospitals with high attempted VBAC rates were less likely t o have cesarean deliveries, more likely to have successful VBACs, and more likely to experience uterine ruptures. Conclusion: Uterine rupture occurs at a low rate in women with and without prior cesarean delivery. Risk of rupture is increased among women with prio r cesarean delivery and among those who attempt VBAC. (Obstet Gynecol 1999; 94:985-9. (C) 1999 by The American College of Obstetricians and Gynecologis ts.).