VBAC: When is it safe?
When do risks outweigh benefits, in light of ACOG’s newly cautious advisory? What conditions call for extra concern?
VBAC is not an option where facilities fall short
Despite meeting VBAC criteria for previous incision or pelvic adequacy, many US women do not have the option of a trial of labor. The reason: the need for obstetric care providers throughout active labor and the ability to perform an emergency cesarean.1 As a result, many midwives and family practitioners can no longer care for VBAC patients independently.
Continuous monitoring is a must
It is the potential for uterine rupture that places patients at risk for unfavorable obstetric outcomes—and rupture can be hard to predict. A nonreassuring fetal heart rate is the most frequent sign.1 Others are uterine or abdominal pain, vaginal bleeding, loss of station of the presenting part, and hypovolemia.1
Continuous electronic monitoring of the fetal heart has the potential to detect nonreassuring events earlier than intermittent auscultation. Thus, continuous fetal heart rate monitoring has become the standard for women attempting VBAC. When it is unavailable, VBAC should not be offered.
Also crucial: Anesthesiology
ACOG recommends that anesthesia and other personnel be on hand in case emergency cesarean is warranted.1 While teaching hospitals and large referral centers are constantly staffed with obstetricians and anesthesiologists, birthing centers and smaller community-based hospitals often lack such coverage. As a result, some physicians and hospitals have withdrawn VBAC as an option
Reducing medicolegal risk
When a trial of labor results in uterine rupture or other adverse outcomes, the patient is more likely to sue. Informed consent and thorough documentation of the VBAC decision are crucial and should include37:
- Appropriate discussion of maternal and perinatal risks and benefits, and documentation of this exchange.
- A clear statement of the woman’s intention to undergo a trial of labor after cesarean delivery.
- If possible, documentation of previous uterine scar on the prenatal record.
- Appropriate counseling about the increased risk of rupture when labor is induced with oxytocin, and documentation of this discussion.
- Counseling about the increased risk of rupture when a trial of labor follows a previous cesarean by less than 19 months.
- Discussion about decreased likelihood of success if the woman is obese, is of advanced age, or has not had a prior vaginal birth.
Is VBAC availability better for health and happiness?
Many women want the option of a trial of labor after cesarean because it affords them the opportunity to experience vaginal delivery. Women who have undergone both cesarean and vaginal deliveries usually opt for a trial of labor in their next pregnancy.38 When a physician or hospital eliminates VBAC as an option, it can lead to patient dissatisfaction—as well as loss of revenue if a woman seeks care elsewhere.
Risk of placenta accreta
If elective repeat cesarean were the only option, the incidence of placenta accreta would increase over time.
Placenta accreta is strongly linked to placenta previa, a condition recognized to increase as the number of previous cesarean sections rises.39,40 A woman with 2 prior cesareans has a 2% incidence of placenta previa; nearly half of these cases are associated with placenta accreta.41 As a result, complications of accreta such as maternal death, need for substantial transfusion, postoperative infection, and intraoperative urinary tract injuries would be expected to increase if VBAC were abandoned.42
For this reason, it is important to ask about the patient’s childbearing goals. If a large family is planned, the potential risk of placenta accreta should be explained.
Assess for accreta. All patients with a prior cesarean section require careful evaluation of placental location and assessment for possible accreta should placenta previa or a low-lying placenta be identified prenatally.
I have found both ultrasound and magnetic resonance imaging useful in recognizing accreta, allowing for adequate preoperative preparation and more favorable outcomes. If accreta is not detected until the time of elective repeat cesarean, it can be life-threatening for the patient.
Should we abandon VBAC?
An unfortunate result of the initiatives promoting VBAC in the 1980s and 90s was a higher rate of uterine rupture, since many women with previous cesarean were strongly encouraged—even required—to undergo a trial of labor. Now that elective repeat cesareans are again on the rise, the risk of rupture should diminish due to better VBAC patient selection, but will probably remain substantially higher than for repeat cesarean.
What exactly is the risk of rupture?
In 1 population-based, retrospective cohort analysis25 involving 20,095 women with 1 previous cesarean section, researchers found a rate of uterine rupture of 5.2 per 1,000 women when labor was spontaneous, compared with 1.6 per 1,000 women who underwent elective repeat cesarean without labor. For women having labor induced with prostaglandins or by other means, the rates were 24.5 and 7.7 per 1,000, respectively.
