A prior cesarean delivery often means a parent faces a choice between a repeat surgical delivery or attempting a vaginal birth for subsequent pregnancies. The decision is complex, involving a careful balance of personal preference and medical risk factors. The term Trial of Labor After Cesarean (TOLAC) is central to modern obstetrical discussion. TOLAC represents the active attempt to go into labor, whether spontaneously or with medical induction, following a previous C-section. It is considered a reasonable and safe option for many patients who meet specific health criteria.
Defining Trial of Labor After Cesarean and Vaginal Birth After Cesarean
Trial of Labor After Cesarean (TOLAC) is the process where a patient with a history of at least one previous C-section attempts a vaginal delivery. This attempt requires close monitoring in a hospital setting to ensure the safety of both the parent and the baby. The TOLAC process concludes when the baby is delivered, either vaginally or through a repeat C-section.
The goal of TOLAC is to achieve a Vaginal Birth After Cesarean (VBAC), the successful outcome. VBAC is achieved when the delivery is completed vaginally, avoiding major abdominal surgery. If the labor attempt is unsuccessful, the process ends in a Cesarean Birth After Cesarean (CBAC), meaning the patient required an unplanned C-section. TOLAC is the attempt, while VBAC is the result.
Determining Eligibility for TOLAC
A patient’s eligibility for TOLAC is determined by strict medical criteria focused on minimizing the risk of complications, particularly uterine rupture. The most important factor is the type of uterine incision used during the previous C-section; a low transverse incision is required for an attempt. This horizontal cut across the lower, thinner part of the uterus is the least likely to tear during labor.
Patients with a prior classical incision—a vertical cut in the upper, contractile part of the uterus—are advised against TOLAC due to a significantly higher risk of rupture. A patient should typically have only one prior low transverse C-section, though some guidelines allow for two previous low transverse incisions. Conditions that necessitate a C-section regardless of prior history, such as placenta previa, are absolute contraindications.
The birthing facility must provide immediate emergency care, including the continuous availability of an operating room, anesthesia, and surgical staff. Without this capacity for an emergency C-section, a TOLAC attempt is not considered safe. Factors that increase the chance of a successful VBAC, such as a previous vaginal delivery or spontaneous labor onset, influence the decision to proceed.
The Concern of Uterine Rupture
The primary risk associated with a TOLAC attempt is uterine rupture: the complete tearing of the old C-section scar during labor. This tear extends through all layers of the uterine wall, leading to severe hemorrhage for the parent and a sudden loss of oxygen for the baby. While rare, the consequences of uterine rupture are devastating, making it the central concern of the TOLAC process.
The baseline risk of symptomatic uterine rupture during a TOLAC attempt for a person with one prior low transverse C-section is low, complicating approximately 0.47% to 0.98% of attempts. This rate increases with factors such as having two previous C-sections or a short interval between deliveries. The most common sign of a rupture is a sudden, persistent abnormality in the fetal heart rate tracing, often a prolonged drop in the heart rate.
Continuous electronic fetal monitoring is mandated throughout active labor to allow for the earliest detection of this complication. If a rupture is suspected, an immediate emergency C-section is required to prevent serious harm to the baby and to control the parent’s bleeding. Rapid intervention is necessary, meaning TOLAC must only occur in hospitals equipped to handle obstetric emergencies.
Expected Outcomes and Alternatives
For well-selected candidates, the attempt at TOLAC has a favorable chance of success, with studies reporting VBAC rates ranging from 60% to 80%. Those who have had a prior vaginal birth have the highest likelihood of success, sometimes reaching over 90%. Conversely, a failed TOLAC results in an unplanned C-section, which carries a higher risk of complications, such as infection or the need for a blood transfusion, compared to a planned C-section.
The main alternative to TOLAC is an Elective Repeat Cesarean Delivery (ERCD), a planned C-section scheduled before the onset of labor. While ERCD eliminates the risk of uterine rupture during labor, it is still a major surgery with its own risks. These include a longer recovery period, a risk of surgical complications, and an increased risk of placental problems in future pregnancies as the number of C-sections rises.
The choice between TOLAC and ERCD requires a thorough discussion of individual risk factors, the statistical probability of a successful VBAC, and the risks associated with both a successful and a failed trial of labor. The decision involves balancing the lower overall risks of a successful VBAC against the rare but serious risk of uterine rupture during a TOLAC attempt.