Trial of Labor After Cesarean (TOLAC) is a medical option for individuals who have previously delivered via C-section and hope for a vaginal birth in a subsequent pregnancy. This approach represents a significant shift from the historical practice of “once a C-section, always a C-section.” TOLAC allows a patient to attempt labor, under careful monitoring, with the goal of achieving a vaginal delivery. The decision to pursue TOLAC involves a thorough review of the patient’s medical history and a careful evaluation of the potential benefits and risks for both the parent and the baby.
Defining TOLAC and VBAC
TOLAC is the planned attempt at a vaginal delivery following a previous cesarean birth. It describes the process of going into labor, spontaneously or with assistance, with the intention of achieving a vaginal delivery. This is one of two primary choices after a prior C-section; the alternative is an Elective Repeat Cesarean Section (ERCS).
If the labor attempt is successful, the resulting vaginal birth is formally called a Vaginal Birth After Cesarean (VBAC). The key distinction is that TOLAC is the trial of labor, while VBAC is the successful outcome. Not every person who starts TOLAC achieves a VBAC, as labor may require conversion to an urgent C-section if complications arise or if labor does not progress.
Determining Patient Eligibility
The decision to attempt TOLAC relies heavily on assessing the prior surgical history, particularly the type of incision made on the uterus. The safest scenario is having only one previous C-section that utilized a low transverse uterine incision. This incision is a horizontal cut across the lower, thinner part of the uterus.
This scar is structurally stronger and has the lowest risk of tearing during labor. Patients who have had a prior classical incision, a vertical cut in the upper, muscular part of the uterus, are typically not candidates for TOLAC because the risk of uterine rupture is too high.
Other factors that preclude TOLAC include medical contraindications to a vaginal birth, such as placenta previa, where the placenta covers the cervix. Furthermore, the hospital must be equipped with immediately available surgical and anesthesia teams to manage an emergency C-section should the need arise during labor.
Understanding the Key Safety Considerations
The primary safety concern associated with TOLAC is uterine rupture, which is the tearing open of the previous C-section scar during labor. This rare event is a serious obstetrical emergency posing significant risk to both the parent and the baby. For well-screened individuals with one prior low transverse incision, the risk of uterine rupture is low, typically estimated to be less than 1% (0.5% to 0.9%).
When a rupture occurs, it can cause severe internal bleeding, potentially requiring a blood transfusion or, in rare cases, a hysterectomy. The baby’s oxygen supply may also be compromised, which could lead to neurological injury or, in very rare instances, fetal demise. A complete understanding of this low absolute risk is a necessary part of the informed consent process before proceeding with a trial of labor.
Navigating Labor and Potential Outcomes
Labor management during TOLAC is meticulous, requiring continuous electronic fetal monitoring to detect early signs of distress, which may indicate a potential uterine rupture. The fetal heart rate tracing is often the earliest signal that the uterine scar may be separating. Certain medical interventions must be used cautiously.
Labor induction or augmentation with agents like oxytocin (Pitocin) can increase the risk of uterine rupture compared to spontaneous labor. Specific medications for cervical ripening, such as misoprostol, are generally avoided entirely in patients with a prior C-section due to their strong association with increased rupture risk.
TOLAC results in one of two outcomes: a successful VBAC or a failed TOLAC, requiring an urgent conversion to a repeat C-section. For carefully selected candidates, the success rate for achieving a VBAC is high, often ranging from 60% to 80%.