Vaginal birth after cesarean: clinical risk factors associated with adverse outcome.

Objective: The objective of the study was to identify vaginal birth after cesarean (VBAC) success rates and maternal and neonatal complication rates for selected antenatal conditions.

Study Design: This was a population-based cohort study using administrative discharge data for women delivering in California hospitals during 2002.

Results: Among 41,450 women, 29.72% (12,320 of 41,450) had maternal, fetal, or placental conditions complicating pregnancy. Attempted VBAC rates and VBAC success rates varied widely by these clinical condition, ranging from 10% to 73%. The VBAC success rate for low-risk women (no conditions) was 73.76% vs 50.31% for high-risk women (at least 1 condition), P < .0001. Absolute rates of maternal and neonatal complications were low (less than 1-2%), and the rate of adverse events was higher in the high-risk clinical group as compared with the low-risk clinical group.

Conclusion: Variation in rates of VBAC success and childbirth morbidities can be partially attributed to clinical factors complicating pregnancy. Women without such conditions show improved VBAC success and fewer maternal and neonatal complications.