Vaginal Birth After Cesarean Outcomes Related to Increasing # of Prior VBAC
Vaginal Birth After Cesarean Outcomes Related to Increasing # of Prior VBAC
From a prospective US multicenter cohort of 45,988 patients with a singleton gestation and a prior cesarean, 13,532 women that elected to attempt a vaginal birth after cesarean (VBAC) were selected for this secondary analysis. This study was conducted to estimate the success rates and risks of an attempted VBAC according to the number of previously successful VBAC attempts. Outcomes evaluated included VBAC success, maternal major morbidity (e.g., uterine rupture and surgical complications), neonatal morbidity (e.g., intensive care nursery admission and acidemia) and maternal and neonatal death. The VBAC success rate rose incrementally from 63.3 to 91.6% in patients that had from zero to four or more prior successful VBACs. Uterine rupture and peripartum risks decreased by 50% after the initial successful VBAC and did not increase with increasing prior VBAC number. Neonatal morbidity did not increase with increasing VBAC number.
Vaginal birth after cesarean (VBAC) has been a research topic of widespread interest in the last decade, with research focus on characterizing risks and benefits and identifying prognostic factors. The latest data regarding VBAC assesses outcomes in an important subpopulation of patients, namely VBAC candidates with multiple prior successful VBAC attempts. The rate of cesarean delivery in the USA - and in most other developed countries - has fluctuated dramatically over the past 30 years. Between 1970 and 1988, the cesarean delivery rate in the USA rose from 5 to nearly 25% until the advent and wide-spread utilization of VBAC, which was accompanied by a decrease in the cesarean rate to 20.7% in 1996. However, as VBAC experience increased and cases of VBAC-related adverse events were reported, many physicians became concerned about the risk of uterine rupture in patients attempting VBAC. In response to these concerns the VBAC rate plummeted and the cesarean rate began increasing again, peaking at 30.2% in 2005. The increasing rate of cesarean delivery is worrisome from both a public health and individual patient perspective. Patients who undergo cesarean delivery not only have surgical risks in the index pregnancy, but also incur increasing rates of maternal and neonatal morbidity with an increasing number of cesareans. Risks of placenta accreta, maternal bowel injury, ureteral injury, cystotomy, hysterectomy and intensive care admission persistently rise with increasing number of cesarean deliveries. Thus, a policy that universally encourages repeat cesarean in lieu of VBAC could induce a multiplicative rise in delivery complications and a substantial public health burden by dramatically increasing the number of highest-risk patients with multiple cesareans.
Given the maternal morbidity associated with increasing number of cesareans, attempts have been rekindled to offer women with a history of a low transverse cesarean a trial of labor to attempt a vaginal birth. The American College of Obstetricians and Gynecologists (ACOG) states that women with a history of one previous low transverse cesarean delivery, a clinically adequate pelvis, and no prior classical uterine scar or rupture are good candidates for a VBAC trial provided that they are at an institution with adequate resources including physicians and anesthesiologists. Two recent large observational studies have shown that the VBAC success rate is 73.4-75.5% with a 0.7-0.9% risk of symptomatic uterine rupture. Successful VBAC has been associated with several benefits, including shorter maternal hospitalizations, less blood loss, fewer infections and fewer thromboembolic events compared with repeat cesarean. While it has been shown that VBAC is safer when successful, clinicians and patients are still concerned about catastrophic obstetrical outcomes that are most commonly related to or attributed to VBAC failure. Unfortunately, attempts to predict VBAC failure have only been moderately successful and predicting uterine rupture in patients attempting VBAC appears to be untenable largely as a result of the rarity of the morbid event. Although VBAC failure or uterine rupture has not been consistently and reliably predicted, several important risk or protective factors have been identified, which can aid the clinician in counseling. The need for labor induction, increased maternal age, a recurrent cesarean indication (e.g., cephalopelvic disproportion) and non-Caucasian race all increase the risk of an unsuccessful VBAC; while a prior vaginal delivery and a prior VBAC are strongly associated with a successful VBAC attempt.
What has not been elucidated is the impact of the number of previous VBACs on subsequent pregnancy outcomes, including uterine rupture. A long-standing, but unproven concern has been that multiple VBACs (i.e., beyond one) may actually be associated with increased maternal and neonatal morbidity. This fear was based on the biologically plausible hypothesis that an increasing number of labor and vaginal deliveries after the initial cesarean may produce additive strain on the uterine scar. Thus, characterizing the association between multiple VBACs and delivery mode-related maternal and neonatal outcomes is an important research topic.
From a prospective US multicenter cohort of 45,988 patients with a singleton gestation and a prior cesarean, 13,532 women that elected to attempt a vaginal birth after cesarean (VBAC) were selected for this secondary analysis. This study was conducted to estimate the success rates and risks of an attempted VBAC according to the number of previously successful VBAC attempts. Outcomes evaluated included VBAC success, maternal major morbidity (e.g., uterine rupture and surgical complications), neonatal morbidity (e.g., intensive care nursery admission and acidemia) and maternal and neonatal death. The VBAC success rate rose incrementally from 63.3 to 91.6% in patients that had from zero to four or more prior successful VBACs. Uterine rupture and peripartum risks decreased by 50% after the initial successful VBAC and did not increase with increasing prior VBAC number. Neonatal morbidity did not increase with increasing VBAC number.
Vaginal birth after cesarean (VBAC) has been a research topic of widespread interest in the last decade, with research focus on characterizing risks and benefits and identifying prognostic factors. The latest data regarding VBAC assesses outcomes in an important subpopulation of patients, namely VBAC candidates with multiple prior successful VBAC attempts. The rate of cesarean delivery in the USA - and in most other developed countries - has fluctuated dramatically over the past 30 years. Between 1970 and 1988, the cesarean delivery rate in the USA rose from 5 to nearly 25% until the advent and wide-spread utilization of VBAC, which was accompanied by a decrease in the cesarean rate to 20.7% in 1996. However, as VBAC experience increased and cases of VBAC-related adverse events were reported, many physicians became concerned about the risk of uterine rupture in patients attempting VBAC. In response to these concerns the VBAC rate plummeted and the cesarean rate began increasing again, peaking at 30.2% in 2005. The increasing rate of cesarean delivery is worrisome from both a public health and individual patient perspective. Patients who undergo cesarean delivery not only have surgical risks in the index pregnancy, but also incur increasing rates of maternal and neonatal morbidity with an increasing number of cesareans. Risks of placenta accreta, maternal bowel injury, ureteral injury, cystotomy, hysterectomy and intensive care admission persistently rise with increasing number of cesarean deliveries. Thus, a policy that universally encourages repeat cesarean in lieu of VBAC could induce a multiplicative rise in delivery complications and a substantial public health burden by dramatically increasing the number of highest-risk patients with multiple cesareans.
Given the maternal morbidity associated with increasing number of cesareans, attempts have been rekindled to offer women with a history of a low transverse cesarean a trial of labor to attempt a vaginal birth. The American College of Obstetricians and Gynecologists (ACOG) states that women with a history of one previous low transverse cesarean delivery, a clinically adequate pelvis, and no prior classical uterine scar or rupture are good candidates for a VBAC trial provided that they are at an institution with adequate resources including physicians and anesthesiologists. Two recent large observational studies have shown that the VBAC success rate is 73.4-75.5% with a 0.7-0.9% risk of symptomatic uterine rupture. Successful VBAC has been associated with several benefits, including shorter maternal hospitalizations, less blood loss, fewer infections and fewer thromboembolic events compared with repeat cesarean. While it has been shown that VBAC is safer when successful, clinicians and patients are still concerned about catastrophic obstetrical outcomes that are most commonly related to or attributed to VBAC failure. Unfortunately, attempts to predict VBAC failure have only been moderately successful and predicting uterine rupture in patients attempting VBAC appears to be untenable largely as a result of the rarity of the morbid event. Although VBAC failure or uterine rupture has not been consistently and reliably predicted, several important risk or protective factors have been identified, which can aid the clinician in counseling. The need for labor induction, increased maternal age, a recurrent cesarean indication (e.g., cephalopelvic disproportion) and non-Caucasian race all increase the risk of an unsuccessful VBAC; while a prior vaginal delivery and a prior VBAC are strongly associated with a successful VBAC attempt.
What has not been elucidated is the impact of the number of previous VBACs on subsequent pregnancy outcomes, including uterine rupture. A long-standing, but unproven concern has been that multiple VBACs (i.e., beyond one) may actually be associated with increased maternal and neonatal morbidity. This fear was based on the biologically plausible hypothesis that an increasing number of labor and vaginal deliveries after the initial cesarean may produce additive strain on the uterine scar. Thus, characterizing the association between multiple VBACs and delivery mode-related maternal and neonatal outcomes is an important research topic.