Conference Addresses Vaginal Birth After Cesarean

In March, the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) convened a consensus conference on vaginal birth after cesarean (VBAC).¹ Various experts described what is known and not known about the safety of trials of labor after prior cesarean delivery (TOLAC). The group identified "critical gaps" in this area, including the need for enhanced national and state surveillance and improved understanding of factors affecting success rates and risks of uterine rupture, such as provider type, setting, and obstetric management variables. The consensus panel noted that in 1999, the American College of Obstetricians and Gynecologists (ACOG) changed its prior advisement of "encouraging" VBAC to stating that women should be "offered" TOLAC if there were no contraindications.² They also noted that ACOG had added that TOLAC should be "performed only in institutions equipped to respond to emergencies and in settings where physicians capable of performing a cesarean are 'immediately available' to provide emergency care." But after acknowledging information gaps, particularly as to the safety of TOLAC in low-volume and rural settings, and after noting that professional liability concerns had led 30% of ACOG fellows to abandon TOLAC, the panel opined: "Given the level of evidence for the requirement for 'immediately available' surgical and anesthesia personnel in current guidelines, we recommend that [ACOG] . . . reassess this requirement relative to other obstetrical complications of comparable risk, risk stratification, and in light of limited physician and nursing resources."¹

By the early 1990s, VBAC had come to be viewed as a safe and effective strategy to stem what was deemed an alarming increase in US cesarean delivery rates to 23.5% in 1991. The embrace of TOLAC was initially fueled by sanguine outcomes from what appeared to be adequately sized patient series collected in the 1980s, generally at prominent West Coast academic medical centers. For example, in 1985, Paul and associates reported outcomes on 751 patients undergoing TOLAC, noting that 82% achieved vaginal delivery with no procedure-related maternal or perinatal mortality.³

The problem was that TOLAC was neither as successful nor as safe as it was first believed to be. These initial studies were not "real-world," randomized, controlled trials but observations made in highly select populations cared for at quaternary care centers with teams of residents, attending obstetricians, and obstetric anesthesiologists available 24/7. By the late 1990s, ACOG was receiving an alarming number of reports, particularly from rural settings, of catastrophic fetal outcomes following sudden uterine rupture. Thus, it was the acuteness of fetal distress following rupture and the absence of reliable predictors for either successful VBAC or uterine rupture that prompted the change in ACOG position.

The news got worse. In 2001, Lydon-Rochelle and colleagues published a population-based cohort analysis of 20,095 women undergoing a delivery after a prior cesarean. It compared uterine rupture rates for deliveries after elective repeat cesarean without labor with those after spontaneous labor, labor induced by oxytocin, and labor induced with PGs.¹⁰ They reported uterine rupture rates of 1.6, 5.2, 7.7, and 24.5 per 1,000, respectively. These rates were far higher than what was commonly believed and prompted new warnings by ACOG.¹¹