Overview of VBAC
Though once valid, the belief that any woman who has delivered via cesarean section (c-section) is not eligible for later vaginal delivery is no longer true. Vaginal birth after cesarean section (VBAC) has become more common as risks to mother and infant have been reduced.
During c-section, an incision is made in the abdominal and uterine walls, the amniotic sac (bag of waters) is ruptured, and the doctor removes the infant through this incision rather than vaginally. The preferred technique for performing a a c-section is a low transverse (horizontal) incision; however, in certain circumstances, the procedure requires a vertical incision through the abdominal and uterine walls. Vertical incisions are more prone to tearing during subsequent vaginal deliveries than horizontal incisions.
Incidence and Prevalence of VBAC
According to the National Institutes of Health (NIH), about 29 percent of births in the United States in 2007 were by c-sections, and repeat cesareans account for approximately one-third of these. According to the World Health Organization, a rate of 10 to 15 percent may be more desirable.
Repeat c-section is not always necessary, but not all women who are eligible attempt it. In fact, according to the NIH, the number of VBACs in the United States has declined since 1996.
The recent increase in c-sections can be attributed to many factors including:
- fetal monitoring, which indicates when the fetus is in danger,
- medical-legal reasons, and
- delivery of breech infants.
C-section rates are also higher for older women with private medical insurance and higher income than for other groups.
Who are candidates for VBAC?
Candidates for VBAC are women who:
- have had not more than two horizontal (transverse) incisions in the uterus (in contrast to the previously used vertical incision in the uterus) and
- have no history of uterine rupture.
Some candidacy guidelines (e.g., the ACOG Practice Bulletin) recommend that a pregnant woman undergoing VBAC should have an obstetrician and anesthesiologist immediately available to perform a c-section in the event of uterine rupture, which can threaten the lives of the mother and infant. Home births are not recommended for VBAC candidates.
Contraindications for VBAC
Women who have had a vertical incision (or "classic incision") are not considered candidates for VBAC because of their increased risk for uterine rupture. Inadequate obstetrical operating facilities and medical staff (e.g., anesthesiologist, ob/gyn) also indicate that a repeat c-section might be advisable. It is widely accepted that women who have had a uterine rupture in the past should have a c-section rather than attempt vaginal delivery.
Common signs of uterine rupture during labor include:
- abnormal fetal heart patterns,
- abdominal pain, and
- vaginal bleeding.