Monday, November 15, 2010

VBAC redux

Several months ago, I wrote in this blog about the precipitous decline of vaginal births after Cesarean (VBAC) in the U.S., which I attributed in part to the the internalization by obstetric specialists of the medical maxim "hearing hoofbeats, thinking zebras":

Objective data support the notion that labor managed by family physicians and professional midwives is considerably more likely to result in a vaginal birth than labor managed by an Ob/Gyn, even controlling for factors such as maternal age and risk status. It isn't difficult to understand why. If an Ob/Gyn is feeling uncertain about how well a patient's labor is progressing and has an inflated estimate of the probability that something might go wrong (the zebra), it's very hard to resist the temptation to eliminate the uncertainty by delivering the baby surgically, then and there. On the other hand, if the surgeon is at least a phone call away, the family physician or nurse midwife might be more patient with the hoofbeats, betting they're hearing a horse.

In preparation for a consensus development conference on VBAC held in March at the National Institutes of Health, a team of evidence reviewers from Oregon Health and Science University prepared a comprehensive report on the factors associated with successful VBAC delivery and the benefits and harms to the mother and infant from a trial of labor. I summarize this report in the Nov. 15th issue of American Family Physician. Here are the main results:

The risk of uterine rupture was statistically higher in women undergoing a trial of labor (0.47 percent) compared with women undergoing an elective repeat cesarean delivery (0.026 percent). Fourteen to 33 percent of women who experienced a uterine rupture underwent a hysterectomy. Maternal mortality was rare, but higher in women undergoing an elective repeat cesarean delivery (13.4 deaths per 100,000 deliveries) than in those undergoing a trial of labor (3.8 per 100,000). In contrast, trial of labor was associated with higher perinatal mortality (1.3 deaths per 1,000 deliveries) than elective repeat cesarean delivery (0.5 per 1,000). Most studies found no differences in neonatal intensive care unit admission rates.

Bottom line: "most of the differences in maternal and perinatal outcomes between these delivery options are statistically, but not clinically, significant." In July, the American College of Obstetricians and Gynecologists slightly relaxed their previous restrictions on access to VBAC by issuing an updated guideline. Will this guideline change and fresh re-examination of the evidence supporting a trial of labor in patients with a previous Cesarean be enough for VBAC to make a comeback in the U.S.?

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