Effect of hospital volume on maternal outcomes in women with prior cesarean delivery undergoing trial of labor.

The authors examined the association between hospital volume of vaginal birth after cesarean section (VBAC) and VBAC failure, uterine rupture, and maternal morbidity. This was a secondary analysis of data from a retrospective cohort study carried out from 1995 to 2000. Trained nurses extracted detailed information from the medical records of more than 25,000 women with a prior cesarean delivery from 17 community and tertiary-care hospitals in the northeastern United States. The study sample included 12,844 women with prior cesarean section who attempted vaginal delivery with a singleton birth. Annual hospital VBAC volume was divided into tertiles. Primary outcomes included VBAC failure, uterine rupture, and a composite measure of maternal morbidity. The authors used multivariable logistic regression to assess the association between hospital VBAC volume and adverse VBAC outcomes after controlling for confounders. The authors did not find evidence of an association between hospital VBAC volume and the likelihood of adverse outcomes in VBAC after adjustment for patient mix. Other risk factors consistent with prior research were identified, including induction of labor, >/=2 prior cesarean deliveries, preeclampsia, diabetes mellitus, and high birth weight. Prior vaginal delivery was protective against adverse VBAC outcomes. The risk of an adverse VBAC outcome in low-volume hospitals was comparable to that in high-volume hospitals.