The overall cesarean delivery rate between 1970 and 2013 has notably increased from approximately 5% to greater than 32%, becoming the most frequently performed major surgery in the United States. Repeat cesarean sections have contributed significantly to this dramatic increase over the past several decades. When the concept of “once a cesarean, always a cesarean” was questioned, more patients elected to undergo trial of labor after cesarean (TOLAC) in the mid-1980s to mid-1990s. By 1996, the cesarean delivery rate dropped to about 20%, but as the number of patients undergoing TOLAC increased, so did the complication rates. In the following years, the trend has shifted back toward repeat cesarean sections.
The most recent update from the American College of Obstetricians and Gynecologists (ACOG) regarding vaginal birth after previous cesarean delivery outlined factors that help determine the likelihood of success of a trial of labor and provided evidence-based recommendations. The use of epidural analgesia for labor as part of TOLAC received a Level A recommendation.
It is important to assess whether someone is an appropriate candidate for TOLAC. Patients with previous cesarean section are at risk for uterine rupture, and one variable that greatly impacts the probability of uterine rupture is where the prior incision was made on the uterus. Patients with a history of a classic uterine incision, which is defined as a long vertical incision in the upper portion of the uterus, were noted to be at a significantly increased risk for uterine rupture during subsequent pregnancies. Hence, obstetricians largely abandoned the classic uterine incision and started to utilize the low vertical incision. They found, however, that the low vertical incision could inadvertently extend superiorly to the body and fundus of the uterus. Today, the low transverse incision is most commonly used in practice because it heals well and maintains the integrity of the uterus for future pregnancies.
Studies have consistently shown that TOLAC results in a successful vaginal birth after cesarean (VBAC) in approximately 60%–80% of those patients that have had a prior cesarean delivery involving a low transverse uterine incision. As to where the patient lies along this spectrum, involves consideration of their individual characteristics. For instance, there is an increased probability of a successful VBAC if the patient has a history of vaginal delivery before or after a prior cesarean delivery. The overall occurrence of maternal morbidity has not been observed to differ between women who have undergone elective repeat cesarean section versus TOLAC. However, there is a lower maternal mortality rate assigned to those in the latter group. The highest morbidity and mortality associated with TOLAC is due to a failed trial, subsequently requiring a repeat cesarean section. In addition, the overall incidence of uterine rupture is noted to be higher in the TOLAC population. While VBAC is associated with fewer complications than an elective repeat cesarean section, a failed TOLAC can lead to greater complications, namely ...