A vaginal delivery after two prior cesarean sections is referred to as a VBAC-2 or VBA2C. This process begins with a trial of labor after cesarean (TOLAC). For individuals with a history of two C-sections, pursuing a TOLAC is an option, but it requires careful selection and counseling. The decision involves a detailed assessment of specific medical history and current pregnancy factors. Not everyone who desires this path will be an appropriate candidate. Attempting a TOLAC balances the benefits of avoiding major abdominal surgery with increased obstetrical risks.
Determining Candidacy for TOLAC
Candidacy for a trial of labor after two cesarean deliveries is determined by stringent criteria focused on minimizing uterine rupture risk. The most important factor is the type of uterine incision used previously. A TOLAC is generally only considered when both prior cesarean sections utilized a low transverse uterine incision, which is the least likely to tear during labor. Vertical (“classical”) or T-shaped incisions are almost always considered absolute contraindications. These incisions involve the thicker, muscular upper portion of the uterus, and the resulting scar tissue carries a high risk of rupture during contractions. Reviewing the operative reports from previous deliveries is a mandatory first step.
The reason for the previous two cesarean deliveries also influences candidacy. If the indication was a non-recurring issue, such as breech presentation or placenta previa, the likelihood of a successful TOLAC is higher. However, prior cesareans due to labor dystocia (“failure to progress”) suggest a recurring issue with labor biomechanics. This history lowers the estimated chance of a successful vaginal delivery.
The time interval between the last cesarean delivery and the current pregnancy is another factor. A shorter inter-delivery interval is associated with a higher risk of uterine rupture. Guidelines suggest waiting at least 18 to 24 months between the last cesarean and the start of the current pregnancy for optimal scar healing.
Current Pregnancy Requirements
Current pregnancy details also determine eligibility. The pregnancy must be a singleton gestation, and the baby must be in a head-down (cephalic) presentation. The mother should not have complicating conditions that preclude a vaginal delivery, such as placenta previa. A history of at least one successful vaginal delivery is a strong positive predictor. This history indicates the pelvis is adequate for birth and significantly increases the success rate. For carefully selected patients, the success rate for a vaginal birth after two cesareans is reported to be as high as 71 to 72 percent.
Understanding the Elevated Risk of Uterine Rupture
The primary risk associated with any trial of labor after a cesarean is uterine rupture. This is a rare event where the weakened scar tears open during labor contractions. The tear can lead to the baby being expelled into the mother’s abdominal cavity, creating an immediate, life-threatening emergency for both mother and baby.
The risk of uterine rupture is elevated for women attempting a VBA2C compared to those with only one prior cesarean (VBAC1). The incidence during a VBA2C attempt typically ranges between 0.9 and 1.8 percent. This compares to an approximate risk of 0.5 to 1.0 percent for a VBAC1 attempt. Although the risk is higher, the absolute chance remains low and must be balanced against the risks of a planned third repeat cesarean section.
If uterine rupture occurs, the consequences are severe. For the mother, this complication carries a risk of significant hemorrhage, requiring blood transfusions and potentially an emergency hysterectomy. For the baby, rupture can cause fetal distress due to loss of blood supply or oxygen, potentially resulting in severe neurological injury or death.
The possibility of rupture requires the hospital setting and medical team to be prepared for an immediate response. The highest risk of complications occurs when the TOLAC attempt fails and an emergency cesarean delivery is required after labor has already begun.
The Medical Setting and Management of Labor
The medical setting for a VBA2C must meet specific requirements to ensure the safest possible outcome. The attempt must only take place in a facility that has immediate readiness to perform an emergency cesarean delivery. This means an operating room must be staffed and available 24 hours a day with an obstetrician, an anesthesiologist, and surgical support personnel present or immediately accessible.
Labor Monitoring
Continuous fetal heart rate monitoring is strongly recommended once labor begins to closely track the baby’s well-being. Changes in the fetal heart rate tracing are often the first sign that a uterine rupture may be occurring. This surveillance allows the medical team to detect early signs of fetal distress and rapidly transition to an emergency surgical delivery if necessary.
Induction and Augmentation
Spontaneous onset of labor is highly preferred, as it is associated with the lowest risk of uterine rupture and the highest chance of success. While induction is an option for maternal or fetal indications, it is associated with a two- to three-fold increased risk of uterine rupture compared to spontaneous labor.
If labor augmentation is necessary, uterotonic agents like oxytocin must be used with extreme caution and meticulous monitoring. Agents used for cervical ripening, specifically prostaglandins, are generally avoided due to the increased risk of rupture in women with a prior uterine scar. The TOLAC is converted to an emergency cesarean immediately if there is concern for the mother’s or baby’s safety.