Clinical Question: What are the risks associated with trial of labor following cesarean delivery?

Setting: Inpatient (any location)

Study Design: Cohort (prospective)

Synopsis: In this observational study, women with a previous cesarean delivery and a current singleton pregnancy decided whether to pursue a trial of labor (they were not randomized). Among the 45,988 women who qualified for the study at the 19 academic medical centers, 9,013 had clear indications for repeated cesarean and were excluded, as were 3,276 women who presented early in labor without a documented plan for trial of labor. Of the remainder, 17,898 underwent a trial of labor and 15,801 had an elective repeated cesarean delivery.

Women choosing trial of labor were younger, more likely to be black, less likely to smoke, less likely to be married, and much more likely to have had a successful previous vaginal delivery (49.8 versus 15.8 percent). A multivariate analysis adjusted for potential confounders of the two composite outcomes: adverse maternal events (i.e., endometritis, transfusion, uterine rupture, hysterectomy, death, dehiscence, thromboembolic disease, hematoma, cystotomy, bowel injury, and ureteral injury) and adverse neonatal events (i.e., intrapartum stillbirth, hypoxicischemic encephalopathy, and neonatal death). Data were gathered prospectively using standard forms and definitions. Approximately one third of the eligible women underwent a trial of labor (the current national rate is 12.7 percent).

A number of important complications were significantly more common in the trial of labor group, most notably uterine rupture (0.7 versus zero percent), endometritis (2.9 versus 1.8 percent), and uterine dehiscence (0.7 versus 0.5 percent). The rate of maternal deaths did not differ significantly between groups (0.02 versus 0.04 percent). The risk of any adverse maternal event was higher in the trial of labor group (5.5 versus 3.6 percent; number needed to treat to harm [NNH] = 53; 95 percent confidence interval [CI], 43 to 68). Uterine rupture was especially common in women with augmented labor (odds ratio [OR] = 2.4) or induced labor (OR = 2.9). Of the 114 uterine ruptures, nine resulted in neonatal death or encephalopathy. The overall risk of stillbirth, hypoxicischemic encephalopathy, or neonatal death was very low, but was significantly higher in the trial of labor group (0.38 versus 0.13 percent; NNH = 398; 95 percent CI, 269 to 721).

Bottom Line: The risks of trial of labor after cesarean delivery are small but cannot be ignored. The most important is an increase in the risk of neonatal death, stillbirth, or encephalopathy (NNH = 398), which is higher than that occurring in other research (Guise JM, et al. Systematic review of the incidence and consequences of uterine rupture in women with previous caesarean section. BMJ July 3, 2004;329:19–25). This article provides some additional guidance for physicians and patients who must make this decision. (Level of Evidence: 2b)