Vaginal Birth After Cesarean Delivery: Title and subTitle BreakCurrent Status

The dictum "Once a cesarean, always a cesarean" ruled for most of the 20th century.¹ Nevertheless, in the 1970s a small group of women who had prior cesarean deliveries were eager to experience vaginal birth and risked a trial of labor (a purposeful attempt to permit active labor development with progression to vaginal delivery).² Success in such cases led the National Institutes of Health in 1981 to promote trial of labor for patients who had previous cesarean deliveries.²

In 1981, the US rate of successful vaginal birth after a prior cesarean delivery (VBAC) was only 3%, with the overall cesarean delivery rate of 17.9%. By 1997, the incidence of VBAC rose steadily to 27.4%. Despite this dramatic increase in VBACs, the total US cesarean delivery rate rose to only 20.8% during the same time period (Figure 1).^{3 - 4} The American College of Obstetricians and Gynecologists (ACOG) stressed in 1984⁵ and 1995⁶ that VBAC should be offered as an option to patients with fetuses in vertex presentations, with 1 or more low transverse uterine scars, and no known contraindication for vaginal delivery. Informed consent for trial of labor and VBAC remained necessary.

During the 1990s, managed care organizations identified VBAC as a way to save money through shorter hospital stays and use of less costly resources. Many such entities categorically demanded trial of labor in all cases. In 1993, Los Angeles County–University of Southern California Medical Center adopted a policy requiring all women meeting ACOG criteria to attempt VBAC. They calculated that each successful VBAC cost $2300 less than repeat cesarean delivery. By 1997, the County of Los Angeles had paid $24 million to settle 49 claims for adverse outcomes associated with VBAC.⁷ Millions more are expected to be paid to provide lifetime care to children with brain injury after labor complicated by uterine rupture. Denial of patient autonomy was costly in both monetary value and human suffering, and the policy was abandoned in 1995 in favor of informed patient choice.

The Los Angeles County–University of Southern California Medical Center experience also showed that uterine rupture increased dramatically with the number of prior cesarean deliveries.⁸ Such data led ACOG to revise criteria in 1999 restricting VBAC attempts to patients with only 1 or 2 prior cesarean deliveries.⁹ A year later the ACOG Task Force on Evaluation of Cesarean Delivery further restricted this to only 1 prior low transverse cesarean delivery in a hospital setting with capability for immediate response to a maternal or fetal emergency. The task force report analyzed the extensive literature, which generated the current recommendations and is recommended to readers desiring further information.³

The Los Angeles experience was mirrored nationwide as desired cost savings from trial of labor and VBAC could not be demonstrated and cohort studies of neonates born by VBAC and elective repeat cesarean delivery showed no significant difference in fetal morbidity.^{3 ,6} In the current issue of THE JOURNAL, Smith et al¹⁰ report the results of a retrospective cohort study finding that the absolute risk of perinatal death associated with trial of labor following cesarean delivery was low but that the risk was significantly higher than that associated with planned repeat cesarean delivery.

The ACOG bulletin noted that despite 800 citations in the literature, there are no randomized controlled trials to show that maternal and neonatal outcomes are better with VBAC than with repeat cesarean delivery.⁹ At present, there is no hard evidence on the relative risks and benefits of term elective cesarean delivery for nonmedical or nonobstetric reasons compared with vaginal delivery.¹¹

The most severe risk in trial of labor is uterine rupture, which occurs in the range of 0.2% to 1.5% of attempted VBAC in patients who have a low transverse uterine scar.⁹ Uterine rupture can be a catastrophe in which immediate medical response is necessary to save the life of both mother and fetus. Rupture is most likely in patients who had classic (fundal) or other vertical incisions with prior cesarean deliveries or uterine perforation during termination of a prior pregnancy. Low transverse uterine scars are more likely to rupture if the patient has had more than 1 prior cesarean delivery. Any condition that overdistends the uterus can weaken the scar and increase risk, including multiple gestation, polyhydramnios, or fetal macrosomia. The earliest sign of uterine rupture usually is a fetal heart monitor tracing showing bradycardia, tachycardia, or recurrent late decelerations, but change in abdominal configuration, vaginal bleeding, or maternal hypovolemic shock may herald rupture.³ To enhance early detection and intervention most obstetricians prefer continuous internal monitoring of the fetal heart rate with one nurse for each patient attempting trial of labor.

The ACOG recommendation for immediate response for a maternal or fetal emergency has correctly been interpreted to mean that trial of labor or VBAC should not be offered in level 1 or 2 maternity units that lack the necessary teams of obstetrician, pediatrician, anesthesiologist, and support staff in the hospital at all times. However, this may conflict with the philosophy of a patient seeking a natural birth experience who wishes to ambulate, delay or refuse intravenous fluids, and have only intermittent external fetal auscultation instead of internal fetal heart rate monitoring. This scenario is fraught with hazard in the event of uterine rupture as the fetal heart rate pattern is usually one of steady and often rapid deterioration with no early warning sign. Even 5 or 10 minutes' delay can result in significant fetal harm. Nurse midwives and family practice physicians may be more receptive to the natural birth philosophy but must accept significant medical-legal liability risks if they offer patients trial of labor and VBAC and cannot provide immediate, appropriate surgical intervention in the case of maternal or fetal deterioration.

Current standards limit acceptable candidates for trial of labor and VBAC to patients with only 1 prior low transverse scar, 37 to 40 weeks' gestation, fetal vertex presentation, otherwise healthy pregnancy, and who are monitored in a unit with capability to immediately respond to maternal and fetal emergencies such as uterine rupture.³

Informed consent is essential for any patient who requests a trial of labor. Extensive and witnessed discussion with the patients, and documentation of this interchange, is crucial if there is liberalization of the above criteria. This may include trial of labor in a patient who has had 2 or more prior low transverse cesarean deliveries, an unknown or vertical uterine scar, requested induction of labor, or preference to deliver in a unit where time to respond to emergency might be 30 minutes or more with potentially fatal consequences to mother, fetus, or both. Such situations are not absolute contraindications, but require thoughtful individualized appraisal of risks and benefits for the patient and fetus. The ultimate decision for risk acceptance rests with the informed patient; physicians must also choose their risk tolerance regarding availability of VBAC in their practice.

The trend is clearly to avoid formerly permissible situations for VBAC such as multiple gestations, premature or postmature fetuses, possible fetal macrosomia, and unknown uterine scar, all of which are associated with increased incidence of uterine rupture. The risk of uterine rupture is also significantly higher when labor is induced and particularly when a prostaglandin is used during the induction process.¹² Successful VBAC is more likely in women who have had a prior successful vaginal delivery¹³ but many VBAC candidates request repeat cesarean delivery to facilitate tubal ligation.

Vaginal birth after cesarean delivery has been promoted to decrease the cesarean delivery rate. For any individual patient the risks of placenta previa and placenta accreta increase progressively with each succeeding cesarean delivery¹⁴ ; demographic shifts in developed nations show that many women now have only 1 or 2 children, minimizing this particular risk.¹⁵ Many women are delaying pregnancy. In 1970, only 4% of primiparas were older than 30 years. In 1994, that figure had increased to 21%.³ The rate of cesarean delivery is significantly increased in women older than 30 years for many reasons. Risks of cesarean deliveries appear to be as acceptable to many women as the risks of vaginal birth, particularly operative vaginal delivery. Urinary and fecal incontinence, pelvic organ prolapse, and sexual dysfunction have an increased incidence following vaginal delivery.¹⁶ Sonographic studies showed a 28% incidence of rectal sphincter damage in women who had visually undamaged perineums after delivery.¹⁷ As this information has entered the public domain, women are increasingly requesting both primary and repeat cesarean deliveries. This is particularly true of VBAC candidates who realize that the attempt may fail and result in a cesarean delivery in 20% to 40% of trials of labor.⁹

A study of 583 000 births in California¹⁸ provides statistics of intracranial hemorrhage in neonates. In mothers who had cesarean delivery prior to initiation of labor, the rate of intracranial hemorrhage was the lowest, 1 of 2750. When cesarean delivery was performed during labor, the rate tripled to 1 of 907 and if it was done after a failed attempt to deliver vaginally (by forceps or vacuum extraction), the incidence tripled again to 1 of 334. The present increasing cesarean delivery rate reflects in part a decline in operative deliveries by forceps and vacuum extraction spurred by the perception of obstetricians that resorting to cesarean delivery decreases liability because such statistics suggest modern cesarean delivery may be safer than operative vaginal birth.¹⁹

The above statistics also reflect in part that fetal maturity can be determined with a high degree of success in a patient who is monitored from early pregnancy. This permits elective scheduling of a repeat cesarean delivery. Alternatively, repeat cesarean delivery can be done at the first signs of labor to minimize fetal risks associated with unanticipated prematurity.

This enhanced safety of cesarean delivery is reflected in some international statistics. Brazil has up to 80% cesarean delivery rate among private insurance patients and about 50% to 60% overall.²⁰ In these settings, VBAC is almost nonexistent, which is a stark contrast to European countries with VBAC rates of approximately 50%.²¹

Currently, there is no reliable method to select patients who will succeed at VBAC. The International Federation of Gynecology and Obstetrics and ACOG concur that the patient should make the decision to attempt VBAC after thorough counseling of risks and benefits.^{9 ,22} Only the patient can assess those relative values. Unfortunately, clear high-level scientific evidence to guide the decision is lacking. Despite the increasing US cesarean delivery rate, there is increasing demand for cesarean delivery by women who must live with the consequences of adverse outcomes of trial of labor or of traumatic vaginal births. The physicians who care for them on an individual basis understand their concerns and their cumulative decisions produce increasing rates for both primary and repeat cesarean deliveries.²³

The situation has been further confused by the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) designation of VBAC rates as 1 of 3 core measures of pregnancy care, which hospitals must report for the ORYX program starting in July 2002. This JCAHO initiative collects data for development of a nationwide database of performance measures. Many hospital administrators, quality improvement managers, and obstetrical units perceived this as a mandate to boost VBAC rates. In an effort to dispel that incorrect perception, JCAHO sent a letter to all hospitals on December 6, 2001, explaining that "[t]his measure is configured as a neutral measure. Be aware the Joint Commission does not intend to promote VBAC."²⁴

This message must be understood so that maternity units not capable of immediate emergency response will not allow women to attempt trial of labor and VBAC under the mistaken belief that JCAHO expects these units to provide VBAC service. Such units should not use VBAC as a core measure, but should use the option to substitute a different measure appropriate to their actual ranges of obstetrical care. In an unsafe setting VBACs might well be perceived as a deficiency in obstetric care rather than a mark of excellence.

The rise and incipient fall of VBAC exemplifies fundamental shifts in medical care in the past 20 years. Previously, physicians made most medical decisions; control then shifted to managed care dictates. Increasing pressure by both physicians and the public is now shifting decisional authority back to physicians and their patients. However, consumerism is moving control of medical care increasingly into the hands of the patients while physicians serve in more consultative and advisory roles. The current status is thus a state of dynamic tension between women who want a natural birth experience, women who want to avoid potential vaginal birth trauma, entities promoting reduction of the cesarean delivery rate, and the individual physicians who must care for each patient.

In 1997, an expert working group from the Department of Health and Human Services established a 75th percentile target of 37% VBAC for suitable candidates as then defined.³ The current shift of a much more restricted cohort of carefully selected patients into the exclusive domain of tertiary centers, coupled with increased patient autonomy, will drive the national VBAC rate dramatically below that goal.