Wednesday, June 7, 2023
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During the Clinical Update Recommendations Session of the 2005 Annual American Academy of Family Physicians (AAFP) Scientific Assembly, Eric Wall, MD, MPh, Clinical Associate Professor, Departments of Family Medicine, Public Health, and Preventive Medicine, Oregon Health and Sciences University, Portland, Oregon, discussed evidence for and controversies surrounding a Trial of labor after cesarean section (TOLAC).[1] Twenty-six percent of all births in the United States now result in cesarean section, and this rate has been rising steadily in recent years. However, the rate of vaginal birth after cesarean section (VBAC) has been declining steadily. Among women with previous cesarean section, the likelihood of VBAC was 9% in 2003 compared with 19% in 1989.
Guidelines for TOLAC, based on patient-centered outcomes (morbidity, mortality, symptoms, cost, and quality of life), were developed by an AAFP Task Force and published on the AAFP Web site in July 2005.[2] The guidelines apply to women with a history of 1 cesarean section and low transverse incision. The grade levels of the evidence used in the guidelines are as follows:
A Maternity Care Facility is defined as a site with capability for cesarean section. Labor at home and home deliveries are excluded from the guidelines.
The AAFP guidelines were based on an extension of the Agency for Healthcare Quality and Research AHRQ Evidence Report Number 71.[3] A total of 1651 studies on the topic were identified. Of these, only 180 studies were selected as being of sufficient quality to be included in the recommendations. Studies up to March 2004 were included in the analysis.
The recommendations and grade of evidence are summarized as follows by Dr. Wall:[2]
Recommendation 1. All women with 1 previous cesarean delivery with a low transverse incision are candidates for and should be offered TOLAC (grade A).
Recommendation 2. Patients desiring TOLAC should be counseled that their chances of a successful VBAC is influenced by several factors. Positive factors include maternal age less than 40 years; prior vaginal delivery, particularly prior successful VBAC; favorable cervical factors; and nonrecurrent indication for cesarean delivery. Negative factors include increased number of prior cesarean deliveries, gestational age over 40 weeks, birth weight over 4000 g, and induction or augmentation of labor (grade B).
Recommendation 3. Prostaglandins should not be used for cervical ripening or induction with TOLAC because they increase the risk for uterine rupture and reduce the rate of successful vaginal delivery (grade B).
Recommendation 4 (the most controversial). TOLAC should not be restricted to facilities with surgical teams present throughout labor because there is no evidence that these additional resources result in improved outcomes. A management plan for uterine rupture and other potential emergencies requiring rapid cesarean section should be available and documented for each woman undergoing TOLAC. This recommendation differs from the current American College of Obstetrics and Gynecology (ACOG) guidelines and policy[4] (grade C).
Recommendation 5. All factors that may affect a woman's decision to undergo TOLAC should be explored, including recovery time and safety. However, the impact of counseling on maternal decision-making is unclear, as little evidence is available (grade C).
Results of the AAFP Task Force literature review were summarized by Dr. Wall and compared with the 2003 AHRQ report, [3] the main outcomes of which comprised uterine rupture and mortality. Seventy-six percent of women undergoing TOLAC are likely to succeed. Seven observational studies found a reduced success rate (63%) when induction with oxytocin or augmentation was used, and success was reduced even further to 51% if prostaglandins were used for induction. Risk for uterine rupture increased slightly with TOLAC when induction or augmentation was used.
Maternal death and infant mortality did not differ between TOLAC and repeated cesarean section. Infection rates were reported as higher with failed TOLAC than with repeated cesarean section (8% vs 3.5%). Risk for uterine rupture was estimated at 4.8 per 10,000 women with or without TOLAC. Risk for infant death from uterine rupture was reported at 1.5/100,000. There was no literature on quality-of-life issues related to VBAC.
Risk-assessment tools (2 validated scoring systems were identified)[5, 6] were only partially useful in predicting successful vaginal delivery. Individual factors found to be associated with improved outcomes included demographic (younger than 40 years), delivery (spontaneous labor, nonrecurrent indication for delivery), medical (absence of diabetes) and cervical factors. Overall, teaching hospitals had a higher success rate with TOLAC than did community hospitals. The influence of TOLAC counseling on patient decision-making was unclear, as reported in 1 recent review.[7] Dr. Wall suggested that additional factors to consider include perceived recovery time, presence of children at home, partner availability, perceived breastfeeding success, and safety.
Given the limitations of the existing literature,[8,9] Dr. Wall outlined issues for a future research agenda:
Dr. Wells concluded by summarizing a recent publication,[10] not included in the AAFP Task Force review, in which vaginal delivery was attempted by 17,898 women, and 15,801 women has elective repeated cesarean delivery without labor. Symptomatic uterine rupture occurred in 124 women who underwent a trial of labor (0.7%). Hypoxic-ischemic encephalopathy occurred in no infants whose mothers underwent elective repeated cesarean delivery and in 12 infants born at term whose mothers underwent a trial of labor (P<.001). Seven of these cases of hypoxic-ischemic encephalopathy followed uterine rupture (absolute risk, 0.46 per 1000 women at term undergoing a trial of labor), and 2 involved death of the infant.
The rate of endometritis was higher in women undergoing TOLAC than in women undergoing repeated elective cesarean delivery (2.9% vs 1.8%), as was the rate of blood transfusion (1.7% vs 1.0%). The frequency of hysterectomy and of maternal death did not differ significantly between groups (0.2% vs 0.3%, and 0.02% vs 0.04%, respectively). The study concluded that TOLAC is associated with a greater perinatal risk than is elective repeated cesarean delivery without labor, although absolute risks are low. This information is relevant for counseling women about their options after cesarean section.
