Trial of labor after cesarean in the low-risk obstetric population: a retrospective nationwide cohort study.

OBJECTIVE: The purpose of this study was to evaluate the risk of adverse maternal outcomes associated with trial of labor (TOL) after cesarean during subsequent pregnancies in the low-risk population. STUDY DESIGN: We conducted a retrospective cohort study using the Nationwide Inpatient Sample and ICD-9 diagnostic and procedure codes from the years 2003 to 2011. A cohort of low-risk pregnant women with a history of previous cesarean delivery were identified and separated into two groups: TOL and no TOL. Logistic regression analysis was used to calculate odds ratios (ORs) comparing adverse maternal outcomes between these two groups. RESULTS: Out of 7 290 474 registered deliveries, there were 685 137 low-risk women who met inclusion criteria. Of these women, 144 066 (21.0%) underwent a TOL, with rates remaining steady over the course of our study. The TOL group was at increased risk of overall morbidity (OR 1.74, 95% confidence interval (CI), 1.66-1.79), most notably uterine rupture (OR 22.52, 95% CI, 19.35-26.20, P<0.01). A secondary analysis showed no apparent correlation between TOL and concomitant adverse maternal outcomes in cases of uterine rupture. CONCLUSION: Although these outcomes remain rare, low-risk women undergoing a TOL remain at increased risk of adverse maternal events as compared with those who chose elective repeat cesarean delivery.