Do women need to know the uterine rupture rate to make informed choices about VBAC?
The NIH press release about the VBAC Consensus Meeting includes only a single instance of the phrase “uterine rupture.” Having spent 2 1/2 days watching the streaming webcast of the event, my strong sense is that this was by design. During the expert testimony, we heard over and over again that uterine rupture is the most feared outcome of a VBAC. We heard in gripping detail what happens when a uterine scar ruptures in labor, and even saw photographs of the devastation. We heard about deaths and hysterectomies and hypoxic injury to newborns that occurred with uterine ruptures. But after all of that, we heard a rather consistent message that uterine rupture itself is not the issue.
Why’s that? To determine the safety of a practice, it makes sense to look at the death or disability associated with it. Although uterine rupture imposes a high risk of perinatal death, hypoxic injury, and hysterectomy, most uterine ruptures do not in fact result in any of these outcomes. Ruptures are traumatic, devastating, and scary, but they are not in and of themselves “death or disability”. As the lead investigator, Jeanne-Marie Guise said in her testimony to the panel, “uterine rupture is a complex intermediate event.” What women really need to know is, “how will each option affect my health, my baby’s health, and our future?”
This means knowing the likelihood the baby will die or be severely harmed, knowing the likelihood the mother herself will die or be severely harmed, and knowing the long-term consequences of the full range of possible harms. It also, of course, means understanding the benefits of both options. And as obstetrician and bioethicist Anne Lyerly noted in her testimony, everyone applies their own values to the hard data, so two women with the same history and risk factors could make two different choices about mode of birth after a prior cesarean. These values and preferences were delineated by the panel in it’s statement to the media:
Factors contributing to some women’s desire to attempt a trial of labor include desire for their partner’s involvement in the delivery, belief that labor and vaginal delivery can be deeply empowering, enhanced opportunity for maternal-infant bonding, greater ease in establishing breast feeding, and easier recovery. Conversely, scheduling convenience, the desire to avoid labor pain, fear of failed trial of labor, avoidance of possible emergency cesarean section, and desire for surgical sterilization at the time of delivery may all contribute to a preference for planned cesarean delivery.
All of these are legitimate values, and although as educators and care providers we might explore them with women, we should not ultimately judge them.
Getting back to health outcomes, how did each option measure up? The researchers found that health outcomes for both mother and baby were good in the vast majority of women choosing either option. Maternal mortality and serious morbidity tended to be more common with planned repeat cesarean surgery while fetal/newborn mortality and serious morbidity tended to be more common with planned VBAC. Evidence appeared to strongly favor VBAC when the outcomes in future pregnancies were considered, since life-threatening placental problems and other poor outcomes get more common the more cesareans a woman has had. Many important outcomes, including long-term physical and emotional health, have been studied inadequately or not at all. The panel highlighted multiple critical gaps in evidence and called for more research. For specific findings, you can read the abstract and access the entire systematic review of the evidence here.
Statistically speaking, one of the clearest associations in the data was the small but significant excess risk of uterine rupture in women choosing VBAC. But the excess likelihood of this “complex intermediate event” doesn’t begin to tell women the whole story. A laser-like focus on this possibility during decision-making obscures the clinically meaningful outcomes that women and their families care about, many of which favor planned VBAC.