Barriers to VBAC remain in spite of evidence

The use of prostaglandins is more controversial: Based on evidence from several small studies, ACOG concluded in its 2010 bulletin that misoprostol (prostaglandin E₁) for cervical ripening is contraindicated in women undergoing TOLAC. It appears likely that rupture risk increases in patients who received both prostaglandins and oxytocin, so ACOG has advised avoiding their sequential use when prostaglandin E₂ is used. This of course limits the options for the practitioner. Therefore, utilizing a Foley catheter followed by pitocin has been an approach advocated in some cases.

Uterine rupture is not predictable, and it is far more difficult to assess an individual’s risk of this complication than it is to assess the likelihood of VBAC. Still, there is value to discussing with the patient whether there are any other modifiers that could potentially influence the risk of rupture.

Since rates of uterine rupture are highest in women with previous classical or T-shaped incision, for example, it is important to try to ascertain what type of incision was previously used. It is widely appreciated that low-transverse uterine incisions are most favorable, but findings are mixed in regard to low-vertical incisions. Some research shows that women with a previous low-vertical incision do not have significantly lower VBAC success rates or higher risks of uterine rupture. TOLAC should therefore not be ruled out in these cases.

Additionally, TOLAC should not be ruled out for women who have had more than one cesarean delivery. Several studies have shown an increased risk of uterine rupture after two prior cesarean deliveries, compared with one, and one meta-analysis suggested a more than twofold increased risk (BJOG. 2010 Jan;117(1):5-19.).

In contrast, an analysis of the MFMU Cesarean Registry found no significant difference in rupture rates in women with one prior cesarean versus multiple prior cesareans (Obstet Gynecol. 2006 Jul;108[1]:12-20.).

It appears, therefore, that even if having more than one prior cesarean section is associated with an increased risk of rupture, the magnitude of this increase is small.

Just as women with a prior vaginal delivery have the highest chance of VBAC success, they also have the lowest rates of rupture among all women undergoing TOLAC.

Patient counseling

We must inform our patients who have had a cesarean section in the past of their options for childbirth in an unbiased manner.

The complications of both TOLAC and elective repeat cesarean section should be discussed, and every attempt should be made to individually assess both the likelihood of a successful VBAC and the comparative risk of maternal and perinatal morbidity. A shared decision-making process should be adopted, and whenever possible, the patient’s preference should be respected. In the end, a woman undergoing TOLAC should be truly motivated to pursue a trial of labor, because there are inherent risks.

One thing I’ve learned from my clinical practice and research on this issue is that the desire to undergo a vaginal delivery is powerful for some women. Many of my patients have self-referred for consultation about TOLAC after their ob.gyn. informed them that their hospital is not equipped, and they should therefore have a scheduled repeat operation. In many cases they discover that TOLAC is an option if they are willing to travel a half-hour or so.

We need to honor this desire and inform our patients of the option, and help facilitate delivery at another nearby hospital when our own facility is not equipped for TOLAC.

Dr. Landon is the Richard L. Meiling Professor and chairman of the department of obstetrics and gynecology at the Ohio State University, Columbus. He served for more than 25 years as Ohio State’s coinvestigator for the National Institutes of Child Health and Human Development Maternal Fetal Medicine Units Network. He reported having no relevant financial disclosures.