INTRODUCTION — The optimum management of the woman who has undergone a previous cesarean delivery has been debated for over 100 years [1-6]. The increasing primary cesarean delivery rate in recent decades has led to large numbers of women undergoing repeat cesarean deliveries and multiple cesarean deliveries. In 1980, a National Institutes of Health (NIH) Consensus Development Conference report questioned the necessity of routine repeat cesarean delivery and, with endorsement from the American College of Obstetricians and Gynecologists (ACOG) [7-9], encouraged attempts to increase the rate of trial of labor after cesarean delivery (TOLAC). These attempts were highly successful; rates of vaginal birth after previous cesarean (VBAC) increased from 3.4 percent in 1980 [10] to a peak of 28.3 percent in 1996 [11], along with a concomitant decline in total cesarean delivery rates for the United States (figure 1) [12].
As the VBAC rate increased, however, so did reports of uterine rupture-related maternal and perinatal morbidity [13-17]. These adverse outcomes dampened enthusiasm for TOLAC. They also prompted ACOG to issue a practice bulletin in 1998 that cautioned TOLAC should only be attempted in appropriately equipped institutions with physicians ‘readily’ available to provide emergency care [18]. Within nine months, ACOG revised the practice bulletin to say that physicians should be ‘immediately’ available [19], a position endorsed by the American Society of Anesthesiologists (ASA) [20,21]. This one-word change, from ‘readily’ to ‘immediately’ available, may have been the most important factor responsible for the decade-long decline in national VBAC rates, reaching a low of 8 percent in 2007 (figure 1) [22-24]. Two surveys of hospital administrators found that 30 percent of hospitals discontinued allowing TOLAC because they were unable to comply with the immediately available requirement for surgical and anesthesia services and, of the hospitals who continued to offer TOLAC, over half made changes in their policies to accommodate ACOG recommendations [25-27]. Ironically, during this same decade, there were continuing reports describing the success and safety of TOLAC in selected clinical settings [28,29].
A number of interrelated factors, both medical and nonmedical, have contributed to declining TOLAC rates. Concerns about medical liability claims have contributed to reduced access to TOLAC [30,31]. A 2009 Survey of Professional Liability by ACOG found that 91 percent of members who responded reported at least one liability claim against them in their career; 62 percent of claims within the survey period were related to obstetric care [30]. Of those who made changes in their obstetric practice as a result of risk or fear of liability, 25 percent stopped offering TOLAC. Another survey of private practice obstetricians also reported that the risk of liability was an important reason cited for no longer offering TOLAC to their patients [32]. Efforts at medical malpractice tort reform may prompt a change in this trend [33].
There is little information on provider views or preferences regarding the practices and policies of TOLAC. In addition to medicolegal/liability concerns and ACOG/ASA requirements for providers and institutions offering TOLAC, fear of catastrophic complications associated with TOLAC may be another reason providers avoid encouraging it for their patients [25,34].
In 2010, the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) and the Office of Medical Applications of Research (OMAR) of the NIH convened a Consensus Development Conference to study these issues [25]. Their final report summarized the state-of-knowledge concerning the risks and benefits of elective repeat cesarean delivery (ERCD) versus TOLAC in women who have undergone one or more prior cesarean deliveries. These findings are described throughout this topic review, along with summaries of recommendations of various professional organizations regarding the approach to management of a woman with a prior cesarean delivery.
PATIENT COUNSELING — Planning the route of delivery for the woman who has had a previous cesarean delivery should be addressed early in her prenatal care, and can even begin preconceptionally. There are two choices:
- TOLAC with the goal of achieving VBAC. If cesarean delivery becomes necessary, then it is termed a “failed TOLAC.” Overall, the success rate for women who attempt TOLAC is approximately 75 percent [34]. This rate varies among institutions and providers, and is affected by various antepartum, intrapartum, and nonmedical factors (discussed below).
- ERCD, which includes scheduled cesarean delivery, as well as planned but unscheduled cesareans performed because spontaneous labor or another indication resulted in the need for delivery before the scheduled date.
The decision for TOLAC or ERCD should be made by the woman in consultation with her provider. No high-quality trials have been performed comparing the risks and benefits of TOLAC versus ERCD.
With either approach, women who have undergone a prior cesarean delivery are at risk for serious maternal and perinatal complications and should be counseled about the risk and significance of these complications. Importantly, individual patient factors that affect the risks and benefits for each delivery route should be discussed. This is especially important for women who are potentially at higher risk of uterine rupture and its attendant sequelae (see 'Possibly appropriate candidates' below). The decision should also be based on consideration of factors known to affect TOLAC success rates. Ongoing discussion at intervals throughout pregnancy is important, as conditions may arise that alter the risks versus benefits of the planned route of delivery (table 1). (See 'Factors affecting success rate of TOLAC' below and 'Risks and benefits of TOLAC and ERCD' below.)
A woman’s decision regarding route of delivery is influenced by a variety of factors, in addition to obstetrical/perinatal risks, success rate, and availability. Women report that their health care providers’ recommendations and preferences exert a strong influence on their decision whether or not to pursue TOLAC. Other factors underlying women’s preference for TOLAC include prior successful vaginal delivery, future pregnancy plans, family obligations making a speedy return to normal activities postpartum desirable, and desire for their partners’ involvement in labor and birth. Factors identified as advantages of scheduled ERCD include scheduling convenience, ease of sterilization at the time of delivery, and fear of failed trial of labor [25,34].
FACTORS AFFECTING SUCCESS RATE OF TOLAC — As mentioned above, overall, women who attempt TOLAC have an approximate 75 percent success rate [34]. The rate varies among institutions and providers, and is affected by various antepartum, intrapartum, and nonmedical factors (discussed below) (table 2). The highest success rates (over 80 percent) are found among women who have had a successful vaginal delivery before or after their cesarean, who present in active labor, and in whom the indication for the prior cesarean delivery was fetal malpresentation. Conversely, women who have never had a vaginal delivery, need labor induction (especially with an unfavorable cervix), had a previous cesarean for failure to progress or nonreassuring tracing, have a macrosomic infant, or are postterm have a reduced likelihood of a successful TOLAC.
Antepartum factors
Indication for prior cesarean delivery — The rate of successful TOLAC by indication for prior cesarean delivery is 75 percent for fetal malpresentation, 60 percent for nonreassuring fetal heart rate pattern, and 54 percent for failure to progress or cephalopelvic disproportion [34,35].
History of prior vaginal delivery — Women who have had a vaginal delivery before or after their previous cesarean delivery are significantly more likely to have a successful TOLAC than those who have never delivered vaginally (OR for successful TOLAC with prior vaginal delivery 3.90, 95% CI 3.60-4.30; with prior VBAC 4.76, 95% CU 4.35-5.26) [35-41].
Demographic — Hispanic, African American, and Asian women are more likely to pursue a TOLAC, but are less likely to have a successful VBAC when compared with non-Hispanic and white women (OR for successful TOLAC for Caucasians, African Americans, and Hispanics: 1, 0.69, 0.65 respectively) [34,35,42-45]. Increasing maternal age, single marital status, and less than 12 years of education are associated with a reduced likelihood of successful TOLAC [34,35,43,46].
Women over age 35 are less likely to pursue a TOLAC; those that attempt TOLAC are less likely to have a successful VBAC and more likely to experience TOLAC-associated complications [47]. Greater maternal height and body mass index (BMI) <30 kg/m2 are both associated with an increased likelihood of successful TOLAC (OR for successful TOLAC per 5 cm maternal height increase 1.33, 95% CI 1.28-1.37; for BMI >30 kg/m2 0.55, 95% CI 0.51-0.60) [35,42,48]. An interpregnancy interval of less than six months is an independent risk factor for both uterine rupture and maternal morbidity during TOLAC [49].
Maternal medical disease — Data on the effect of preexisting maternal medical disease on the outcome of a TOLAC are inconclusive. Several cohort studies of women with preexisting maternal disease, such as hypertension, diabetes, asthma, renal disease, and heart disease, reported a reduced likelihood of successful TOLAC [35,36,44]. In one prospective study, however, there were no significant differences in the rates of successful TOLAC in women with these medical disorders [42].
Intrapartum factors
Admission labor status — When admitted to the labor unit, women in spontaneous labor or with a high bishop score are more likely to have successful TOLAC than women who are being induced or who have low Bishop scores (ORs for successful TOLAC with spontaneous labor, induction, augmentation 1.0, 0.50, 0.68, respectively; for admission cervical examination >4cm 2.56, 95% CI 2.38-2.67) [34,35].
Fetal macrosomia — A fetus weighing more than 4000 g reduces the likelihood of successful TOLAC (OR for successful TOLAC for birth weight >400g 0.55, 95% CI 0.49-0.61) [34,35,50,51].
Type of hospital — University hospitals or those affiliated with an obstetrics and gynecology residency program have higher rates of TOLAC and successful VBAC [46,51,52]. Women who deliver at a private or rural hospital have a decreased likelihood that TOLAC will be attempted, and if attempted, a decreased rate of successful VBAC when compared to a tertiary care or perinatal center [34]. As an example, a study that compared VBAC rates across hospital settings in California reported rates of VBAC (adjusted for baseline and medical characteristics of mother and fetus) were 14 percent in private nonteaching hospitals, 57 percent in public hospitals, 60 percent in private teaching hospitals, and 41 percent in health maintenance organizations [53].
RISKS AND BENEFITS OF TOLAC AND ERCD — There are three possible outcomes for the woman who has had a prior cesarean delivery: a successful trial of labor culminating in vaginal birth (successful VBAC), an unsuccessful TOLAC resulting in a repeat cesarean delivery, or an ERCD. The benefits of TOLAC are closely related to having a successful vaginal birth, which is associated with the lowest morbidity of the three possibilities. The highest risks for maternal and neonatal morbidity are associated with unsuccessful TOLAC that culminates in a repeat cesarean delivery [16].
When counseling women concerning the risks and benefits of TOLAC versus ERCD, it is important to recognize that many studies that compared these two routes of delivery reported maternal and neonatal outcomes based on the actual route of delivery rather than the intended route. If this type of analysis is performed, the outcomes of women who undergo cesarean delivery after an unsuccessful TOLAC are grouped along with the outcomes of women undergoing ERCD. In addition, the outcomes of women who planned ERCD, but spontaneously labored and were delivered vaginally, are grouped along with the outcomes of women who had a successful VBAC. This method of analysis leads to misleading conclusions about the actual risk of adverse events or outcomes associated with the decision to attempt TOLAC or ERCD [25,34,54]. Analysis of available data is also complicated by imprecise definitions and outcome measurements, as well as difficulties encountered when trying to characterize events and outcomes attributable to route of delivery.
Overall estimated risk — The NICHD consensus conference panel determined the following risk estimates based on data obtained by systematic review [34,54].
- In a hypothetical group of 100,000 women of any gestational age who undergo TOLAC, there will be 4 maternal deaths, 468 cases of uterine rupture, and 133 perinatal deaths [54].
- In a hypothetical group of 100,000 women of any gestational age who undergo ERCD, there will be 13 maternal deaths, 26 uterine ruptures, and 50 perinatal deaths [54].
In terms of absolute risk for the woman undergoing TOLAC, 1 in 1000 trials of labor will result in neonatal death or significant neurological injury [55]. Specifically, 1 in 100 trials will result in uterine rupture, and 1 in 10 uterine ruptures will result in neonatal death or neurological injury. The absolute risk of uterine rupture with ERCD is 0.026 percent (95% CI 0.009-0.082%) [34].
Maternal risks — The following table summarizes available evidence on maternal risks of TOLAC and ERCD (table 3). These data were derived from a systematic review of 41 studies on the maternal outcomes for trial of labor versus ERCD that reported on the actual route of delivery rather than the intended route.
Uterine rupture — Uterine rupture is a life-threatening pregnancy complication; it is rare (in resource-rich countries), but when it occurs, it is most often associated with TOLAC. The term refers to complete disruption of all uterine layers, including the serosa. It often leads to maternal hemorrhage and adverse fetal outcomes. By comparison, uterine dehiscence generally refers to an incomplete, and frequently clinically occult, uterine scar separation where the serosa remains intact, and is not usually associated with hemorrhage or adverse outcomes.
Risk — The overall risk of uterine rupture in women with a prior cesarean delivery is 0.3 percent [25,28,34]. There is no reliable way to predict which women will have a rupture, but the risk is higher in women who undergo TOLAC and lower in women who undergo ERCD [25,54]. Based on available data, the best estimate of the risk of uterine rupture at term is 0.78 percent with TOLAC and 0.22 percent with ERCD [25,54].
The risk of rupture varies depending on the type and location of the prior uterine incision. In the Maternal Fetal Medicine Units Network study of 45,988 women with a singleton gestation undergoing TOLAC, the uterine rupture rate was significantly lower when the prior uterine incision was low transverse than when it was low vertical (0.7 versus 2.0 percent) [28].
Intrapartum factors reported to increase the risk of rupture include lower Bishop Score on admission to Labor and Delivery and labor induction with either oxytocin or a prostaglandin [34,56]. Factors inconsistently reported to be associated with increased risk of rupture include increasing maternal age, advancing gestational age, birth weight exceeding 4000 g, interdelivery interval <18 to 24 months, and single-layer uterine closure [34,56]. None of these risk factors is sufficiently reliable to be clinically useful for prediction of this catastrophe.
On the other hand, a prior vaginal delivery, either before or after the prior cesarean delivery, significantly reduces the likelihood of uterine rupture (OR 0.26-0.62 for prior vaginal delivery, OR 0.52 for prior successful TOLAC) [34].
A number of predictive models for uterine rupture using a combination of risk factors have been described, but none have proven to be reliable clinically [34,56].
Use of imaging to predict risk of uterine rupture — Imaging techniques have been used in an attempt to predict women at increased risk of uterine rupture, with mixed results. The most common technique is ultrasound measurement of the thickness of the lower uterine segment in the third trimester. A systematic review of 12 studies of sonographic lower uterine segment thickness for predicting the risk of uterine scar defect rupture could not determine an ideal cut-off [57]. The optimal cut-off value varied from 2.0 to 3.5 mm for full lower uterine segment thickness (smallest measurement between the amniotic fluid and urine in the maternal bladder) and from 1.4 to 2.0 mm for thickness of the myometrial layer (smallest measurement of the hypoechoic portion of the lower uterine segment). When the lower uterine segment thickness was thin, the pooled odds ratio of uterine rupture was 11.2 (95% CI 6.5-19.4); when the myometrial thickness was thin, the pooled odds ratio of uterine rupture was 5.2 (95% CI 2.5-10.8). At least one case report has described a catastrophic uterine rupture with complete extrusion of fetus and placenta and neonatal acidosis in a woman whose sonographic lower uterine segment measurement exceeded 3.5 mm [58]. Thus, there is no clinically useful ultrasonic measurement of the lower uterine segment in late pregnancy that is 100 percent predictive or protective of catastrophic uterine disruption.
The natural history of uterine defects diagnosed in the postpartum period if the woman subsequently becomes pregnant is unknown. One study performed ultrasounds of the uterine scar at 6 to 9 months postpartum in 162 women who delivered by cesarean delivery and volunteered for this study, and then collected delivery outcome data for those who became pregnant [59]. Results of the ultrasound study were not given to the patient or her clinician. In the first subsequent pregnancy after ultrasound examination, most (10/13) women with deep uterine scar defects had no scar problems at delivery: four underwent uncomplicated vaginal delivery, two had an instrumental vaginal delivery, and four had a cesarean delivery with no signs of uterine dehiscence or rupture. Four uterine dehiscences/ruptures were detected during the 26 repeat cesarean deliveries: one occurred among the 19 women with an intact scar or shallow scar defect and three occurred among the seven women with deep scar defects.
It is even more difficult to predict the pregnancy-related risk of uterine rupture when uterine defects (also called niches) are found on imaging studies of nonpregnant women several months after delivery. Such women may be asymptomatic or present with lower abdominal pain or abnormal uterine bleeding [60]. On ultrasound, the defect appears as a hypoechogenic or nonechogenic area in a region of myometrial thinning [61,62]. It is typically covered by a thin layer of myometrium and/or peritoneum.
There are no guidelines for management of these uterine scar defects. Repair of the defect, including excision of the fibrotic tissue and vaginal or laparoscopic closure of the anterior uterine wall, has been described and successful pregnancy delivered by scheduled cesarean has been reported [60,63].
Diagnosis and management — Premonitory signs of uterine rupture include fetal heart rate (FHR) abnormalities (reported in 33 to 100 percent of cases), vaginal bleeding, abdominal pain, and uterine contraction abnormalities. FHR patterns associated with uterine rupture are consistently reported to be nonreassuring.
Findings of FHR tracings in women with uterine rupture and adverse neonatal outcomes were evaluated in two case-control and one observation study [64-66]. Complete extrusion of the fetus and placenta was the most important factor associated with neonatal acidosis [64,65]. In two studies, there was significant neonatal morbidity with TOLAC when the interval between recognition of FHR abnormalities and delivery was ≥18 minutes [64,66]. However, delivery in less than 18 minutes is not totally predictive of neonatal well-being because another report described hypoxic-ischemic encephalopathy in 2 of 23 neonates with an intervention time <18 minutes [65].
It is not surprising that prompt intervention will not always successfully prevent these adverse outcomes because their severity is linearly dependent on the extent of placental separation that can follow uterine rupture. This exists as a spectrum varying from no separation to total placental abruption and the partial degrees of separation may increase over time. At its worst, total placental separation as an immediate consequence of rupture would require delivery of the fetus in less than five minutes to reduce the risk of fetal death or hypoxic-ischemic encephalopathy, a nearly impossible task in any delivery unit.
Outcome — A number of serious adverse outcomes are associated with uterine rupture. These may primarily involve the mother or her fetus/neonate, but both are frequently affected.
The 2010 NIH Consensus Development Conference statement on vaginal birth after cesarean report did not find any reports of maternal death associated with uterine rupture [25], but a 10-year review of severe maternal outcomes in Canada reported 4 maternal deaths among 1879 cases of uterine rupture in women with no major preexisting medical conditions (one death per 500 uterine ruptures) [67].
Maternal morbidity was assessed in a literature review of 880 cases of uterine rupture during 142,075 TOLACs (6.2 ruptures per 1000 trials of labor) [68]. For every 1000 trials of labor, the rate of uterine rupture-related complications was 1.8 for packed red blood cell transfusion, 1.5 for pathologic fetal acidosis (cord pH<7.00), 0.9 for hysterectomy, 0.8 for genitourinary injury, 0.4 for perinatal death, and 0.02 for maternal death.
The most common serious maternal complication is hysterectomy, which has been reported in 14 to 33 percent of women with a uterine rupture. Hysterectomy is indicated when the uterine defect is irreparable or in the setting of uncontrollable maternal hemorrhage. Comorbidities of hysterectomy include operative injuries such as urinary tract or bowel lacerations, blood transfusion, and postoperative infection [25,34].
The two devastating perinatal outcomes associated with uterine rupture with TOLAC are perinatal death (stillbirth or neonatal death) and neurological injury from hypoxia or acidosis. The perinatal death rate associated with uterine rupture is 5 to 6 percent [25,69]. In a study by the Maternal-Fetal Networks, the incidence of neonatal hypoxic-ischemic encephalopathy associated with uterine rupture was 7 cases among 114 infants born after uterine rupture (6 percent) and two of these seven neonates died [28]. There were no neonatal deaths or cases of hypoxic-ischemic encephalopathy among women undergoing ERCD. Prompt intervention after uterine rupture did not always prevent severe acidosis and neonatal morbidity and mortality [65].
Maternal mortality — Any increased risk of maternal mortality for women with a prior cesarean delivery is difficult to quantify because maternal death is rare. When a literature review compared maternal mortality ratios by actual route of delivery, the rate in women who delivered by repeat cesarean was significantly higher than the rate in women who delivered vaginally (13.4 versus 3.8 per 100,000 live births) [54]. Uterine rupture is the most important cause of maternal death during TOLAC, and, as discussed above, is associated with a maternal death rate of approximately 1 per 500 uterine ruptures [67].
Other risks
- Infection — While intrapartum chorioamnionitis is more common with TOLAC, the incidence of postpartum pelvic infection is lower after a successful TOLAC than after either ERCD or cesarean delivery following an unsuccessful TOLAC [28].
- Hysterectomy — The risk of hysterectomy in women with a prior cesarean delivery is about 0.3 percent, with no differences based on planned or actual route of delivery [28,34]. Although some of these procedures are performed because of uterine rupture, many are due to placenta accreta, which becomes more prevalent with an increasing number of cesarean deliveries. (See "Diagnosis and management of placenta accreta".)
- Hemorrhage and transfusion — Data comparing the risk of hemorrhage or blood transfusion for TOLAC versus ERCD are sparse.
- Pelvic floor injury — There are few data about long-term effects on the pelvic floor after TOLAC versus ERCD [25]. ERCD avoids the risk of perineal trauma during labor and vaginal birth, and any attendant sequelae. (See "Pelvic floor disorders associated with pregnancy and childbirth".)
Maternal benefits — The benefits of successful TOLAC derive from avoidance of risks associated with repeat cesarean delivery. Immediate benefits of TOLAC include shorter hospital stay, fewer postpartum complications, quicker return to normal activities, and lower maternal morbidity and mortality. Long-term, the potential complications that accrue with multiple cesarean deliveries can be avoided.
The benefits of ERCD are scheduling convenience, ease of sterilization at the time of delivery, and avoidance of the risks associated with failed TOLAC [16]. (See "Cesarean delivery: Postoperative issues", section on 'Complications' and "Repeat cesarean delivery", section on 'Is there an unsafe number of repeat cesarean deliveries?'.)
Perinatal risks and benefits — There is little or no evidence on short- and long-term neonatal outcomes after TOLAC versus ERCD [25]. As discussed above, most of the available evidence documents differences comparing actual rather than intended mode of delivery, and is of low quality due to inconsistent and imprecise outcome measures [25].
Mortality — TOLAC is associated with significantly higher perinatal mortality and neonatal mortality rates compared with ERCD (perinatal mortality rate: 0.13 versus 0.05 percent; neonatal mortality rate: 0.11 versus 0.06) (table 4) [25,34].
Hypoxic ischemic encephalopathy — TOLAC appears to be associated with a higher risk of hypoxic ischemic encephalopathy than ERCD. The Maternal Fetal Medicine Networks Unit study of over 33,000 women with a prior cesarean delivery reported the incidence of hypoxic ischemic encephalopathy at term was 46 per 100,000 TOLACS compared with zero cases in women undergoing ERCD [28].
Respiratory problems — Analysis of pooled data suggests that the absolute risk of transient tachypnea of the newborn is slightly higher with ERCD compared with TOLAC (4.2 versus 3.6 percent) [54]. However, neonatal bag and mask ventilation was used more often in infants delivered following TOLAC than in those delivered by ERCD (5.4 versus 2.5 percent).
Other complications — There are no significant differences in five-minute Apgar scores or neonatal intensive care unit admissions when infants delivered by TOLAC are compared with those delivered by ERCD [54].
Birth trauma from lacerations is more commonly seen in infants born by ERCD.
OPTIMUM CANDIDATES FOR TOLAC — The paucity of definitive data that are predictive of maternal and fetal outcome (successful or unsuccessful) from TOLAC makes determining the ideal candidates for a trial of labor a challenge. A number of predictive models, screening tools, and nomograms have been developed for this purpose, but none have been proven to be clinically useful [25,34,42].
Screening tools and decision aids for choosing the route of delivery — Screening tools and decision aids have been developed to help predict the likelihood of successful TOLAC and to help patients understand the risks and benefits of TOLAC versus ERCD.
Provider screening tools — Ideally, a reliable screening tool can help identify women with a prior cesarean delivery who have a high or low likelihood of successful TOLAC. Current screening tools use a combination of obstetric factors, such as maternal demographics (age, race, ethnicity, BMI); the indication(s) for the prior cesarean delivery; the type and number of prior hysterotomy incisions; previous vaginal deliveries, either before or after the cesarean delivery; cervical favorability (eg, Bishop score at the time of admission for spontaneous or planned induction of labor); and intrapartum interventions (eg, labor induction or augmentation) [25]. One review concluded that currently used scored screening tool models incorporating various combinations of the above predictive factors reasonably predicted successful TOLAC, but were unable to consistently identify women at risk for failed TOLAC [70].
Patient decision aids — A number of patient-oriented information and decision aids are available to help patients make an informed decision about TOLAC versus ERCD. Patient information is available from ACOG at www.acog.org/publications/patient education/bp006.cfm and from the National Library of Medicine at www.nlm.nih.gov/medlineplus/ency/article/002911.htm.
Additionally, there are online tools or decision aides that can be used as an adjunct to provider consultation. They are designed to communicate evidence-based information to help patients better understand childbirth choices, establish their personal priorities, and ultimately decide whether or not to pursue a TOLAC. One example is from the Mayo Clinic: Vaginal Birth After C-section and is available at http://www.mayoclinic.com/health/vbac/MY01143.
Recommendations by national organizations — The following guidelines were developed by a panel of the NICHD consensus conference on delivery after prior cesarean and by ACOG (table 5) [25,34,71]. The NICHD concluded: “Given the available evidence, trial of labor is a reasonable option for many pregnant women with one prior low transverse uterine incision. The data reviewed in this report show that both trial of labor and elective repeat cesarean delivery for a pregnant woman with one prior transverse uterine incision have important risks and benefits and that these risks and benefits differ for the woman and her fetus. When trial of labor and elective repeat cesarean delivery are medically equivalent options, a shared decision-making process should be adopted and, whenever possible, the woman’s preference should be honored” [25,34].
Recommendations from other professional societies are shown in the table (table 6) [72].
Appropriate candidates
One prior low transverse uterine incision — There is good and consistent evidence that a woman who has undergone only one previous cesarean delivery performed using a transverse lower segment hysterotomy incision has a very low risk of uterine scar separation during a subsequent trial of labor; thus, TOLAC is a reasonable option for delivery [25,34]. For these women, the bulk of evidence supports a success rate of TOLAC approaching 60 to 70 percent, with a predicted uterine rupture rate of about 0.7 percent [34]. Success rates are higher in patients with additional characteristics, such as a prior vaginal delivery. (See 'Factors affecting success rate of TOLAC' above and 'Uterine rupture' above.)
Possibly appropriate candidates — Data regarding risk of uterine rupture in the following situations are more limited and based on sparse or inconsistent scientific evidence [71]. ACOG recommends that after individualized risk assessment and counseling, patients in the following situations be considered candidates for TOLAC [71].
Prior low vertical uterine incision — Data from reports beginning in the 1980s are limited and inconclusive regarding TOLAC outcomes in women with a prior low vertical uterine incision. An early study reported no significant difference in the risk of symptomatic uterine rupture during TOLAC for women with a prior low vertical incision versus those with a prior low transverse incision (0.8 versus 1.0 percent) [73]. In contrast, a Maternal Fetal Medicine Units Network study found significant differences in the rates of uterine rupture during TOLAC by the type of previous hysterotomy incision [28]. The rate of rupture by incision type was low transverse (0.7 percent), low vertical (2.0 percent), unknown (0.5 percent), and 1.9 percent in women who had a prior classical or inverted T- or J-incision and presented in advanced labor or declined repeat cesarean delivery.
Among the authors and editors of this topic, one of four offers TOLAC to women with a prior low vertical uterine incision as long as there are no additional concerns, such as risk factors for difficult urgent cesarean delivery (eg, obesity, intraabdominal adhesions) or risk factors for placental insufficiency (eg, fetal growth restriction, oligohydramnios).
Multiple prior low-transverse uterine incisions — A systematic review with meta-analysis of five cohort studies of uterine rupture in women with prior cesarean deliveries found that women undergoing TOLAC after two prior cesareans were at significantly higher risk of rupture than those with one prior cesarean (1.59 versus 0.72 percent) [74]. The absolute risk of rupture after two cesareans was higher in all five studies, but the difference was not statistically significant in two of these five studies.
Among the authors and editors of this topic, one of three offers TOLAC to women with two prior low transverse uterine incisions, as long as there are no additional concerns, such as risk factors for difficult urgent cesarean delivery (eg, obesity, intraabdominal adhesions) or risk factors for placental insufficiency (eg, fetal growth restriction, oligohydramnios).
Unknown type of uterine incision — The prior incision type is not always available when caring for a woman in her subsequent pregnancy. Because most women with a prior uterine incision for common obstetrical indications have had a low-transverse hysterotomy incision, some authors suggest making the decision for TOLAC based on this assumption. This approach is supported by data from a Maternal-Fetal Medicine Units Network study that found women who had an unknown type of prior incision had a similar rate of uterine rupture as those with a known prior low-transverse uterine incision (0.5 and 0.7 percent, respectively) [28].
However, there are a few indications for cesarean delivery that increase the probability of a prior vertical incision, such as breech delivery remote from term or transverse lie, thus, the circumstances of the prior cesarean delivery should be considered in estimating whether the patient is at increased risk of uterine rupture.
Among the authors and editors of this topic, one of three offers TOLAC to women with an unknown uterine incision, as long as there are no additional concerns, such as risk factors for difficult urgent cesarean delivery (eg, obesity, intraabdominal adhesions) or risk factors for placental insufficiency (eg, fetal growth restriction, oligohydramnios).
Pregnancy more than 40 weeks of gestation — Studies have consistently observed that women who attempt TOLAC beyond 40 weeks of gestation are less likely to successfully deliver vaginally [25,50,71,75]. In addition, there are at least two reports that have described a 2 to 3 percent risk of rupture in these women [76,77].
Multifetal gestation — While most studies report that women with a twin gestation are significantly less likely to pursue a TOLAC, the overall success rate and risk of uterine rupture in this population is similar to that in singleton gestations undergoing TOLAC [78]. (See "Twin pregnancy: Labor and delivery", section on 'Trial of labor after previous cesarean delivery'.)
Macrosomia — Identification of suspected macrosomia by any definition adds another factor to consider during decision-making for TOLAC versus ERCD. While most women with a previous cesarean delivery, a prior vaginal birth, and an estimated fetal weight of about 4000 g will have a successful TOLAC, we advise women with a macrosomic fetus and no prior history of a vaginal delivery against TOLAC because of a lower likelihood of success and a higher likelihood of adverse obstetrical outcomes, in particular, an increased risk of uterine rupture [79-81].
Fetal demise — (See "Diagnosis and management of stillbirth", section on 'Options for women with a previous cesarean delivery'.)
Inappropriate candidates — Most clinicians believe the risks of TOLAC outweigh the benefits in the following settings [71]:
High-risk uterine scars — Types of prior hysterotomy incisions that have an unacceptably high risk for uterine rupture with a TOLAC include: classical, T or J incisions, as well as transfundal incisions or myoma resections that extend into the myometrium. As discussed above, a Maternal Fetal Medicine Units Network study of TOLAC evaluated the outcome of women with prior classical or either inverted T or J incision who presented in advanced labor or declined repeat cesarean delivery [28]. These women had a uterine rupture rate of 1.9 percent. A subsequent retrospective study of women attempting TOLAC found that a prior inadvertent uterine extension at the time of primary cesarean was associated with an increased risk of uterine rupture when compared with no prior extension (6.0 versus 1.5 percent) [82].
Prior uterine rupture — Women who have experienced a previous uterine rupture confined to the lower uterine segment are reported to have a high incidence (6 percent) of recurrent uterine rupture with labor [83-87]. Women in whom the prior rupture involved the upper uterine segment have experienced a repeat rupture rate as high as 32 percent [83]. In a 25-year literature review, 22 women identified to have uterine rupture subsequently became pregnant again [86]. Twenty underwent ERCD at term; the other two women died following catastrophic uterine rupture at 32 and 35 weeks of gestation. (See "Repeat cesarean delivery", section on 'Previous classical incision'.)
If pregnancy is undertaken after repair of uterine rupture, it should be delayed a minimum of 18 to 24 months, given indirect evidence that a short interpregnancy interval has been associated with an increased risk of rupture in women undergoing TOLAC. Women with prior uterine rupture, prior Classical cesarean delivery, or prior hysterotomy for fetal surgery [88] are all at increased risk of scar dehiscence or rupture in subsequent pregnancy and thus should undergo delivery by ERCD prior to term. (See "Interpregnancy interval and pregnancy outcome", section on 'Uterine rupture during trial of labor' and "Repeat cesarean delivery", section on 'Previous classical incision' and "Rupture of the unscarred uterus", section on 'Counseling about future pregnancy'.)
Obstetrical complications — ERCD should be performed when standard obstetrical indications for cesarean delivery are present, such as placenta previa or footling breech presentation.
Lack of an appropriate facility — ERCD should be performed when factors related to the facility, including availability of the surgical, anesthesia, nursing, and pediatric staff and resources to provide multiple transfusions of blood and blood products, preclude optimal care of the woman with ruptured uterus (see 'Facilities and personnel' below).
LABOR AND DELIVERY CONSIDERATIONS
Facilities and personnel — The ability to perform emergency cesarean delivery is a prerequisite for attempting TOLAC in women with any type of prior hysterotomy incision. As discussed above, a joint statement of the ASA and ACOG stated that TOLAC should be undertaken only in facilities with immediate availability of appropriate resources, including equipment and personnel (obstetric anesthesia, nursing personnel, a physician capable of monitoring labor and performing an emergency cesarean delivery, personnel and equipment for neonatal resuscitation) [19-21].
In situations in which such resources are not immediately available, ACOG recommends a discussion between the provider and patient to discuss implications of the lack of immediately available personnel [71]. One antepartum option is referral to another facility with appropriate resources to obtain optimal outcomes. In all cases, any decision to plan for TOLAC in the setting with lack of immediately available resources should be made only after careful consideration by the woman and her health-care provider. In such instances, the discussion and plan should be documented in the obstetrical record.
Induction and augmentation of labor — While there is no conclusive evidence that uterotonic drugs administered to women with a prior cesarean delivery increase the risk of uterine rupture, epidemiological studies suggest that this is the case. For this reason, we suggest a cautious approach to labor induction or augmentation in women undergoing TOLAC, especially those with an unknown type of uterine scar, unfavorable cervix, or gestational age over 40 weeks [50,89,90].
Induction — Some women who plan TOLAC will develop a maternal or fetal indication for delivery before the onset of labor. Two concerns about inducing labor in these women are observational studies that show an increased risk for uterine rupture with labor induction and a lower probability of successful TOLAC. A prior vaginal delivery or favorable cervix (eg, Bishop score of >6) increases the probability of successful TOLAC with labor induction. The method of induction can also affect the outcome: induction with oxytocin appears to have a lower risk for uterine rupture than prostaglandins. These issues are discussed in detail separately. (See "Cervical ripening and induction of labor in women with a prior cesarean delivery".)
In a practice bulletin, ACOG recognized induction of labor for maternal or fetal reasons as an option for women undergoing TOLAC [71]. ACOG and others recommend that misoprostol (prostaglandin E1) not be used for cervical ripening or labor induction in the third trimester in women with prior uterine incisions, and strongly discourage use of other prostaglandins, as well [71,91-94]. If the cervix is dilated and favorable, our preference is to perform amniotomy to induce labor.
Augmentation — There are conflicting data on the risk of uterine rupture from oxytocin augmentation of labor during TOLAC. Three large observational studies reported an increased risk for uterine rupture with labor augmentation (OR 2.3-14; actual rate of rupture 0.9-1.9 percent) [28,95,96], and two others did not find an increased risk [29,97]. Small numbers of uterine ruptures and use of prostaglandin analogues for cervical ripening prior to augmentation of labor prevent definitive conclusions based on these results.
Because of the paucity of high-quality data and the relative infrequency with which uterine rupture occurs, ACOG supports use of oxytocin for augmentation of labor in women with a previous cesarean delivery [71].
Intrapartum monitoring — Given an increased risk of uterine rupture, most experts recommend continuous monitoring of uterine activity and fetal heart rate during TOLAC; there are no data to show superiority of external versus internal monitoring methods [71]. Intrauterine pressure monitoring is unnecessary, as it is an insensitive method for early diagnosis of uterine rupture [98,99].
Analgesia and anesthesia — Epidural analgesia may be used to provide adequate pain relief during labor [71].
Uterine exploration at delivery — Some clinicians recommend routine uterine exploration following uncomplicated successful TOLAC, while others only perform exploration for standard obstetrical indications, such as retained placenta or hemorrhage [100]. There are no data on the value of routine examination to identify asymptomatic uterine dehiscence or whether repair is indicated.
Among the authors and editors of this topic, two of three do not perform routine uterine exploration after vaginal delivery in women with a prior cesarean delivery.
SUMMARY AND RECOMMENDATIONS
- Pregnant women with a prior cesarean birth must choose between elective repeat cesarean delivery (ERCD) and a trial of labor after cesarean delivery (TOLAC). We feel the decision regarding mode of delivery must be made by each woman after informed discussion with her physician. The final assessment depends upon her individual clinical circumstances, tolerance for the various risks involved, and ability to give birth in a facility capable of emergency cesarean delivery if required. (See 'Patient counseling' above.)
- In a hypothetical group of 100,000 women at term who undergo TOLAC rather than ERCD, there will be 10 fewer maternal deaths, 650 additional uterine ruptures, and 50 additional neonatal deaths. In terms of absolute risk for the woman undergoing TOLAC, 1 in 1000 trials of labor will result in neonatal death or significant neurological injury. Specifically, 1 in 100 trials will result in uterine rupture, and 1 in 10 uterine ruptures will result in neonatal death or neurological injury. (See 'Overall estimated risk' above.)
- Approximately 75 percent of women who attempt TOLAC will be successful; this rate varies upon the clinical situation that led to the first cesarean birth. It is highest in women with a previous successful TOLAC, previous vaginal delivery, previous cesarean delivery for nonvertex presentation, and women with spontaneous onset of labor. The combination of previous cesarean for failure to progress or nonreassuring tracing, no previous vaginal delivery, and induced labor has a particularly poor prognosis. (See 'Factors affecting success rate of TOLAC' above.)
ACKNOWLEDGMENT — The authors and UpToDate would like to acknowledge Drs. J Gerald Quirk, MD, PhD and Julie Welischar, MD, who contributed to earlier versions of this topic review.
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