Overview of VBAC
Though once valid, the belief that women who have delivered via cesarean section (c-section) are 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 and because of the benefits. 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. In certain circumstances, c-section requires a vertical incision through the abdominal and uterine walls, which is more prone to tearing during subsequent deliveries than the scar left by the current technique of a low transverse (horizontal) incision.
According to the Centers for Disease Control and Prevention (CDC), more than 29% of births in the United States are 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% may be more desirable. Repeat c-section is not always necessary; successful VBAC could decrease these numbers, but not all women who are eligible attempt it. In 1995, only 27% (about 76,000) of candidates attempted vaginal birth after cesarean section.
The increase in c-sections over the past decades is 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.
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.
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.
A cesarean delivery is major surgery, with all of the associated risks. When successful, VBAC is safer than c-section. VBAC is associated with a small risk of uterine rupture, but it is considered to be a safe option for some by the American College of Obstetricians and Gynecologists (ACOG). The uterus is a hollow, muscular organ. A uterine rupture is a surgical emergency that occurs during labor and sometimes before labor starts. The uterine wall tears at the site of a prior surgical incision and sometimes tears as a result of weak uterine muscle tissue (caused by multiple pregnancies or infection). The infant may be expelled from the uterus into the mother's abdominal cavity, which can result in infant brain damage or death.
The incidence of uterine rupture with VBAC in a mother who has had a low transverse incision is approximately 0.2–1.5%.
Accompanying the elevated risk of uterine rupture is an increased risk for hysterectomy (surgical removal of the uterus). However, most cases are managed by controlling the bleeding and repairing the tear surgically. Also, there are indications that a failed attempt at VBAC followed by a c-section increases the rate of infection in infants and mothers.
There is no conclusive evidence that labor induced with pitocin or prostaglandin gel creates a risk in VBAC. However, some studies indicate that the use of prostaglandin gel in VBAC cases may increase the risk of uterine rupture, hemorrhaging, and hysterectomy in the mother and of subsequent fetal distress and infant death.
Some of the benefits of VBAC are as follows:
- Epidural analgesia
- Fewer medical risks to mother and baby
- Less blood loss and fewer blood transfusions
- Less risk for infection for mother and infant
- Lower cost
- Shorter post-delivery recovery time for the mother
The success rate for VBAC is approximately 60–80% and can be higher if the patient had a vaginal delivery prior to c-section. In patients who had a c-section performed because of dystocia (abnormal or difficult labor), the success rate is lower. The most common causes of difficult labor include:
- Cephalopelvic disproportion or "CPD" (the infant is too large for the pelvis)
- Failure to progress (contractions are not productive; cervix does not dilate; labor lasts too long)