Neonatal outcomes unknown with different delivery methods

June 1, 2010

There is much physicians do not know about the risks and benefits of a woman attempting to deliver vaginally after having a cesarean birth.

There is much that we do not know about the risks and benefits of a woman attempting to deliver vaginally after having a cesarean birth, including what's best for the baby, according to a statement prepared from the proceedings of National Institutes of Health (NIH) Consensus Development Conference, Vaginal Birth After Cesarean: New Insights, held recently in Bethesda, Maryland.

Unlike with maternal outcomes, says the statement, there is little or no evidence on short-term or long-term neonatal outcomes after a trial of labor (TOL) compared to an elective repeat cesarean delivery (ERCD).

The statement says that for cesarean births in general, infants have "increased rates of short-term respiratory sequelae, problems with mother-infant bonding, and breastfeeding initiation. Long-term consequences may include asthma." However, studies to date have not specifically examined outcomes for TOL after a prior cesarean delivery versus ERCD.

A separate evidence report written for the conference notes that from 1990 to 1996, the VBAC rate increased from 19.9% to 28.3%, but since that time it has dropped so that now more than 90% of women who have had a cesarean delivery repeat with another cesarean delivery. Overall, the cesarean delivery rate increased from 21% in 1996 to 33% in 2007.

The consensus report notes that about one-third of hospitals and one-half of physicians no longer offer TOL, despite the fact that TOL success is consistently high (60% to 80%) and the risk of uterine rupture is low (<1%). One reason given for reduced VBAC is concern about uterine rupture during TOL.

The statement says that good evidence is lacking regarding whether there are differences between infants delivered via TOL compared with those delivered via ERCD in regard to respiratory sequelae, sepsis, breastfeeding initiation, or mother-infant bonding.

However, a rare catastrophic outcome for infants, hypoxic ischemic encephalopathy (HIE), which happens in 1 of about 1,000 births, is one of the most serious consequences of uterine rupture and a major reason that women and clinicians have fears about attempting TOL, according to the consensus statement.

A recent observational study of more than 35,000 women found an HIE incidence of 12 cases in TOL versus none in ERCD. However, the statement says, "The studies on this important outcome are limited by inconsistency in study methodology."

The consensus statement also says that some studies found that the neonatal mortality rate is higher for TOL at 110 per 100,000 compared to 50 per 100,000 for ERCD.

But the evidence is very limited. "It is fair to say that for any of these outcomes, a large high-quality study could change the magnitude or direction of effect" of the evidence presented, said Cathy Emeis, PhD, CNM, assistant professor at the Oregon Health and Science University, who summarized the studies for the meeting.

The evidence report, also noting the lack of quality studies, says that it is important to identify and study the most meaningful infant outcomes, in addition to agreeing on definitions and methods of ascertainment. That includes evaluation of variation in gestational age associated with ERCD and TOL with or without induction.

The panel recommends that hospitals, providers, and policymakers collaborate on creating integra- ted services that could mitigate or eliminate the current barriers to TOL and that they continue to work on the medico-legal issues that may make the problem worse.

The report concludes that TOL is a reasonable option for many women with a prior transverse uterine incision. It also says that both TOL and ERCD have important risks and benefits and that those differ for the woman and her infant.

The committee specifically urged the American College of Obstetricians and Gynecologists and the American Society of Anesthesiologists to reassess their guidelines that say that TOL services should be allowed only where there is "immediate availability" of capabilities, including obstetric anesthesia and a physician capable doing an emergency delivery.

The draft statement, the extensive evidence report, and a conference Webcast can be found at the Web site http://consensus.nih.gov/2010/vbac.htm.

The nearly 400-page evidence report, prepared for the Agency for Healthcare Research and Quality, includes discussion of current evidence on the benefits and risks of these delivery methods to the baby.