Vaginal birth after cesarean delivery, commonly referred to as VBAC, is a delivery option for patients who have had one prior c-section. Recently the technical terminology has changed a bit, referring to the labor process as TOLAC (trial of labor after cesarean), and successful completion of a vaginal delivery as VBAC. However, the term VBAC still tends to be the most widely used and understood abbreviation.
VBAC allows an option for experiencing a vaginal birth, and successful VBAC avoids additional abdominal surgery and provides a quicker post-partum recovery. For those planning large families, VBAC enables one to avoid multiple repeat c-sections and the associated surgical risks.
TOLAC is safest in a hospital where emergency cesarean delivery is immediately available and staff is immediately available to provide emergency care. At Kamm McKenzie OBGYN our physicians are always in the hospital with our laboring patients, and therefore we are able to safely offer VBAC as an option to our patients.
Who is a candidate for VBAC?
TOLAC is a reasonable option for many women who have undergone one previous LOW TRANSVERSE CESAREAN DELIVERY. This term “low transverse” refers to how the incision was made on the uterus, not the abdomen. For patients interested in VBAC, your provider will request a copy of your prior operative report to confirm that the incision on your uterus is indeed, low transverse. In some special circumstances, it may be appropriate for a patient with two prior LOW TRANSVERSE c-sections to TOLAC if she has already had a successful vaginal delivery. However, there is potentially an increased risk of uterine rupture in this circumstance.
What are the risks of VBAC?
It is important to remember that both repeat cesarean delivery and VBAC have risks associated with them, and the highest risks are associated with a failed VBAC. Either of these may be associated with maternal hemorrhage, infection, and hysterectomy. However, the risk most commonly associated with VBAC is uterine rupture, meaning that during the labor process the uterus ruptures , or breaks open, on the prior uterine scar line. In rare instances uterine rupture may occur with a routine scheduled c-section. Uterine rupture is associated with both maternal and fetal complications. The risk of uterine rupture in a patient who has had one prior low transverse cesarean delivery undergoing TOLAC is 0.7-0.9%. The risk of a catastrophic event, such as fetal or maternal death, is less than 1/1000 or 0.1%.
What is the success rate for VBAC?
For anyone considering VBAC, the indication for your prior c-section impacts the likelihood of successful VBAC. For example, a patient who had a prior c-section for arrested labor (ie the cervix stopped dilating or one reached 10 cm but pushed for a few hours without making progress), has the lowest likelihood of VBAC. On the other hand, someone who has had a prior successful vaginal delivery has the highest likelihood of success. The overall success rate for VBAC is 60-80%.
Factors that affect achieving a successful VBAC
Factors That Increase Probability of Successful VBAC:
- Prior vaginal delivery
- Spontaneous labor
Factors That Decrease Probability of Successful VBAC:
- History of prior arrested labor
- Advanced maternal age
- Gestational age > 40 weeks
- Maternal obesity
- Increased neonatal birth weight
- Short interval between prior c-section and current pregnancy
Is there a role for labor induction with VBAC?
Induction of labor for maternal or fetal indications is an option for a patient desiring VBAC. However, keep in mind that spontaneous labor is one of the key factors predicting success. Induction of labor is also associated with a slightly higher uterine rupture risk, although the studies vary, a conservative estimate would be ~ 1.5% risk of uterine rupture.
