Fighting VBAC-Lash: Critiquing Current Research

By Jill MacCorkle
Issue 110, January/February 2002

For updated information about ACOG's stance on VBACs read "ACOG Recommends Vaginal Birth After Cesarean (VBAC) as Safe and Appropriate," July 23, 2010.

The July 5, 2001, issue of the New England Journal of Medicine contained a study by Mona Lydon-Rochelle et al.1 and an accompanying editorial by Michael F. Greene, MD,2 which together generated much media attention and discussion of the risks of vaginal birth after cesarean (VBAC). Although the study actually contains little new or groundbreaking information and relies on questionable data collection, news media--and even some physicians--are claiming that it indicates a greater risk for uterine rupture than previous research has shown. Headlines across the nation have suggested that research now supports repeat cesarean section over VBAC, and a growing number of physicians have opined that cesarean section is as safe or safer than vaginal birth.

But take a closer look: what physicians are inadvertently admitting is that their overuse of medical intervention in childbirth has succeeded in making the average vaginal birth as risky as major surgery. A careful critique exposes the limitations of both the study and the current medical model of childbirth, raising the question of whether that model still holds any credibility for pregnant women.

Study Results
The study used Washington State birth certificate data in combination with hospital discharge data from the years 1987 to 1996 to examine the incidence of uterine rupture in four groups of women: those who had an elective repeat cesarean section (ERCS) without labor (n=6,980), those who attempted VBAC with spontaneous onset of labor (n=10,789), those who had labor induced by non-prostaglandin methods (n=1,960), and those whose labor induction included prostaglandins (n=366). The uterine rupture rate for women having a scheduled elective repeat cesarean was 0.16 percent, or 11/6,980. For women with spontaneous onset of labor (SOOL), the rate was 0.54 percent (56/10,789); with non-prostaglandin induction, the rate was 0.77 percent (15/1,960); and for women with induction which involved prostaglandins, the rate was 2.45 percent (9/366).

None of these rates is significantly different from those found in previous studies. In fact, the rate of rupture among women having a trial of labor was lower than many recent studies have suggested. The rate for all women attempting VBAC was 0.6 percent, which falls on the low end of the 0.2 to 1.5 percent range cited by the American College of Obstetricians and Gynecologists (ACOG) in a review of the literature for their VBAC practice guidelines.3 Rates of 0.5 to 1.0 percent have been used in the past as evidence for the relative safety of VBAC; those who are using those same rates now to suggest that VBAC is too risky are engaging in an egregious display of statistical sleight of hand for the purpose of limiting women's access to VBAC. The motivations behind this movement are discussed in the conclusions of this article.

It is certainly not newsworthy to find that elective repeat cesarean does not completely protect a woman from the risk of rupture. It is the prior cesarean, not VBAC, that exposes mother and baby to the risk of uterine rupture. A prior cesarean scar also predisposes the mother and baby to other obstetrical complications that are rarely seen in women with intact uteri. Physicians know well that cesareans cast a long shadow over the rest of a woman's reproductive life, one that can affect both her and her unborn children's health and safety. Yet the cesarean rate reached 22.9 percent in 2000, an 11 percent increase over the previous four years and the highest rate reported since 1989.4 Clearly, physicians are not doing enough to reduce the number of unnecessary cesareans (conservatively estimated at 50 percent of all cesareans, or approximately 500,000 per year).5 Therefore, they must bear the responsibility for the complications that their often cavalier use of surgical intervention continues to cause; proposing further surgery as a solution will only compound the problem.

The most notable finding of the New England Journal of Medicine study--and one that has barely made a ripple in the news media--is the dramatic increase in risk of rupture seen with induction of labor that includes the use of prostaglandins. Although previous studies have linked powerful synthetic hormones used to induce labor with an increased risk of rupture, this study attempted to isolate the use of prostaglandins as a distinctly separate risk factor and expressed it in terms of relative risk with respect to elective repeat cesarean. The rate of rupture among women induced with prostaglandins was 15 times higher than that of women who did not labor at all. When compared to the risk of rupture for women who entered labor spontaneously, the rupture rate with prostaglandin induction was nearly five times higher. This should give caregivers and expectant women pause before they consider induction of labor after a previous surgical delivery, which is alarmingly common today.