VBAC Revisited

Abstract & Commentary

In some hospitals Vaginal Birth After Cesarean (VBAC) has been eliminated as an option for patients having had previous Cesarean sections. Although the major reason stated for this position has been risk of uterine rupture, there is more to this stance which involves potential liability and the inconvenience to providers of having to be immediately available for the duration of these patients’ labors.

The NICHD network recently tackled the job of nailing down (again) the real risk of rupture during VBAC. In an observational multi-center trial, Landon and colleagues reviewed outcome data from 17,898 women opting to have VBAC and 15,801 women having elective repeat Cesarean sections. Landon et al were predominantly interested in the rate of symptomatic uterine rupture, which was 7/1000 in the VBAC group and the incidence of neonatal encephalopathy, which occurred in 12 cases in the VBAC group (and in none of the elective Cesarean group). Actually, only 7 of these cases of hypoxic encephalopathy were associated with uterine rupture. The remaining 5 were seemingly secondary to fetal compromise before and during in labor. Landon et al lumped together the 12 cases which resulted in a rate of neonatal encephalopathy of 0.46 per 1000 at term in those electing to have a trial of labor, but actually was only 0.27 per 1000 when associated with uterine rupture.

The need for transfusion and the complications of postpartum endometritis was higher in the VBAC group, but the need for hysterectomy was no different between groups (Landon MB, et al. N Engl J Med. 2004;351(25):2581-2589).

Comment by John C. Hobbins, MD

From this study (and others), it is clear that there is a risk of symptomatic uterine rupture and neonatal encephalopathy in patients with VBAC but it very small (< 1:1000). The incidence of neonatal encephalopathy in the VBAC group without rupture was identical to the overall rate of this condition reported in all laboring patients (1.6 per 10,000).

What was somewhat under-played was the association between rupture and the use of oxytocics either to induce (1%) or augment labor (0.9%). Interestingly, the rate of rupture of spontaneous labor in VBAC was only 0.4% which gave a likelihood ratio of 1.0.

Landon et al were not able to detect a major effect of prostaglandins. However, a very recent investigation has shown that uterine rupture with oxytocin tended to occur more frequently away from the uterine scar in 64% of cases, while those in whom prostaglandins were used had a rupture in the old scar in 90% of cases.1 This suggested that prostaglandins had a direct scar softening effect which is certainly not a desired tendency when attempting a VBAC.

The Cesarean rate is now 26% and climbing. To me, there is no doubt that there should be a well ensconced place for VBAC in those motivated to have it (after being presented with the above information). From the available information, the success rate is good (it was 73% in the above study), and the risk of rupture, especially if oxytocics are avoided is extremely low. If rupture is avoided the risk of neonatal encephalopathy is no greater than for any laboring patient.


1. Buhimschi CS, et al. BJOG. 2005;112:38-42.

John C. Hobbins, MD, Professor and Chief of Obstetrics, University of Colorado Health Sciences Center, Denver, is Associate Editor for OB/GYN Clinical Alert.