Disclosures: C Edward Wells, MD Nothing to disclose. F Gary Cunningham, MD Nothing to disclose. Charles J Lockwood, MD, MHCM Consultant/Advisory Boards: Celula [Aneuploidy screening (Prenatal and cancer DNA screening tests in development)]. Equity Ownership/Stock Options: Celula [Aneuploidy screening (Prenatal and cancer DNA screening tests in development)]. Susan M Ramin, MD Nothing to disclose. Vanessa A Barss, MD, FACOG Nothing to disclose.
Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through a multi-level review process, and through requirements for references to be provided to support the content. Appropriately referenced content is required of all authors and must conform to UpToDate standards of evidence.
INTRODUCTION — The optimum delivery 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 one or more repeat cesarean deliveries. In 1980, a National Institutes of Health (NIH) Consensus Development Conference report questioned the necessity of routine elective repeat cesarean delivery (ERCD) 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: the TOLAC rate reached a peak of 51.8 percent in 1995, with a concomitant decline in total cesarean delivery rates for the United States .
As the TOLAC rate increased, however, so did reports of uterine rupture-related maternal and perinatal morbidity [11-15]. 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 . Within nine months, ACOG revised the practice bulletin to say that physicians should be “immediately” available , a position endorsed by the American Society of Anesthesiologists (ASA) [18,19]. This one-word change, from “readily” to “immediately” available was associated with a decade-long decline in national TOLAC rates, which reached a nadir of 15.9 percent in 2006 before increasing again .
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 [20-22].
Concerns about medical liability claims have also contributed to reduced access to TOLAC [23-25]. For example, 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 . Of those who made changes in their obstetric practice as a result of risk or fear of liability, 25 percent stopped offering TOLAC. Fear of catastrophic complications associated with TOLAC may be another reason providers avoid encouraging it for their patients [20,26]. In spite of these concerns, it is important to remember that a successful uncomplicated TOLAC has many short- and long-term benefits (discussed below) and, in a Markov model, when the likelihood of success was ≥47 percent, TOLAC was more effective and less expensive than ERCD . Cost-effectiveness increases in patients who undergo multiple subsequent vaginal deliveries .
This topic will review issues related to choosing the route of delivery after cesarean birth, as well as management of a trial of labor in this setting. In 2010, the United States National Institute of Child Health and Human Development (NICHD) and the Office of Medical Applications of Research of the NIH convened a Consensus Development Conference to study these issues . Their final report summarized the state-of-knowledge concerning the risks and benefits of ERCD versus TOLAC in women who have undergone one or more prior cesarean deliveries. These findings are described throughout this topic, along with more recent data and summaries of recommendations of various professional organizations regarding the management of women with a prior cesarean delivery.
No large randomized trials have been performed to provide comparative data on outcomes 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 TOLAC. 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 [20,26,29,30]. 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.
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 begin preconceptionally. The decision for trial of labor after cesarean delivery (TOLAC) or elective repeat cesarean delivery (ERCD) should be made by the woman in consultation with her provider. 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 (see 'Risks and benefits of TOLAC and ERCD' below). 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 and 'Inappropriate candidates' below). The decision should also be based on the estimated success rate and consideration of factors known to affect TOLAC success rates. Between 1990 and 2009, the success rate for women in the United States who attempted TOLAC ranged from 39 to 70 percent . The success rate varies among institutions and providers and is affected by various antepartum, intrapartum, and nonmedical factors (see 'Characteristics that increase the probability of successful TOLAC' below) . Ongoing discussion at intervals throughout pregnancy is important, as conditions may arise that alter the balance of risks and benefits of the planned route of delivery.
Similarly, 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 healthcare 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, the desire to experience a natural birth, 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, fear of failed trial of labor and emergency cesarean delivery, and avoidance of labor pain [20,26].
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, a failed TOLAC resulting in a repeat cesarean delivery during labor, or an ERCD. The medical and obstetrical benefits of successful TOLAC derive from avoidance of the risks associated with repeat cesarean delivery, and especially multiple cesarean deliveries. Similarly, the medical and obstetrical benefits of ERCD derive from avoidance of risks associated with TOLAC. Thus, the benefits of TOLAC are closely related to having a successful vaginal birth, which is associated with the lowest morbidity of the three possibilities. ERCD is associated with the second lowest rate of morbidity . Failed TOLAC is associated with higher morbidity than successful TOLAC or ERCD. The highest rate of maternal and neonatal morbidity occurs with uterine rupture, which can be fatal.
Unlike most medical decisions where a patient is comparing risks and benefits, the pregnant patient must compare risks and benefits for both herself and her fetus and the risks and benefits for the two individuals sometimes do not align: a decision that increases maternal risk may be associated with fetal benefit. It should also be noted that most pregnant women are willing to tolerate a high degree of risk to themselves in exchange for zero or near zero risk for their child [32,33].
Maternal risks and benefits — The following table summarizes available evidence on maternal risks of TOLAC and ERCD (table 1). 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.
Risks to consider when choosing a route of delivery include (table 1):
●Uterine rupture – Uterine rupture is a life-threatening pregnancy complication; the incidence is low (in resource-rich countries), but when it occurs, it is most often associated with TOLAC. Rupture refers to a complete disruption of all uterine layers, including the serosa, that 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. (See "Uterine dehiscence and rupture after previous cesarean delivery".)
The United States National Institute of Child Health and Human Development (NICHD) consensus conference panel determined the following overall risk estimates based on data obtained by systematic review [26,29].
•In a hypothetical group of 100,000 women of any gestational age who undergo TOLAC, there will be 468 cases of uterine rupture, 4 maternal deaths, and 133 perinatal deaths .
•In a hypothetical group of 100,000 women of any gestational age who undergo ERCD, there will be 26 uterine ruptures, 13 maternal deaths, and 50 perinatal deaths .
In terms of absolute risk for the woman undergoing TOLAC, 1 in 100 trials of labor will result in uterine rupture, and 1 in 10 uterine ruptures will result in neonatal death or neurological injury, thus 1 in 1000 TOLACs will result in neonatal death or significant neurological injury . The absolute risk of uterine rupture with ERCD is 1 in 4000 (0.026 percent, 95% CI 0.009-0.082 percent) .
●Infection – There is no significant difference between TOLAC and ERCD in maternal infection rate. 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 .
●Peripartum hysterectomy – The risk of peripartum hysterectomy in women with a prior cesarean delivery is about 0.3 percent, with no significant differences based on planned or actual route of delivery [26,35]. 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 "Repeat cesarean delivery", section on 'Is there an unsafe number of repeat cesarean deliveries?'.)
●Hemorrhage and transfusion – Data comparing the risk of hemorrhage or blood transfusion for TOLAC versus ERCD are sparse and inconsistent, but generally do not indicate a significant difference [30,36].
●Pelvic floor injury – There are few data about long-term effects on the pelvic floor after TOLAC versus ERCD . ERCD avoids the risk of perineal trauma during labor and vaginal birth, and any attendant sequelae. (See "Urinary incontinence and pelvic organ prolapse associated with pregnancy and childbirth".)
●Maternal mortality – Maternal mortality is a rare event for both TOLAC and ERCD. A systematic review of data based on the actual mode of delivery (rather than the intended route) revealed the overall risk of maternal death is significantly lower with TOLAC compared with ERCD (3.8/100,000 versus 13.4/100,000; RR 0.33, 95% CI 0.13-0.88) [26,29].
●Thromboembolism – The risk of postpartum venous thrombosis or embolism appears to be the same for TOLAC and ERCD and is rare .
●Failed TOLAC – Maternal morbidity is higher when TOLAC fails (ie, cesarean delivery performed during labor) than when TOLAC results in vaginal birth. The performance of a cesarean in labor increases the risks associated with surgical wounds, hemorrhagic complications requiring hysterectomy or blood transfusion, and infectious complications (postpartum endometritis) .
Benefits to consider when choosing a route of delivery:
●Convenience – ERCD is typically scheduled, allowing the patient and her family the ability to make specific work-life plans for the delivery and postpartum period. TOLAC is most successful when labor is spontaneous, and thus somewhat unpredictable.
●Length of hospitalization and recovery – Immediate benefits of successful TOLAC include shorter hospital stay, fewer postpartum complications, and quicker return to normal activities compared with ERCD.
●Sterilization – Postpartum sterilization is readily accomplished at cesarean delivery. This is only a minor advantage, as sterilization can be performed after a vaginal birth, often immediately following the birth.
Perinatal risks and benefits — There is little or no evidence on short- and long-term neonatal outcomes after TOLAC versus ERCD . 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 .
●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), although the absolute risk is very low [20,26].
●Hypoxic ischemic encephalopathy – TOLAC appears to be associated with a higher risk of hypoxic ischemic encephalopathy (HIE) than ERCD: the NICHD 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 . Although the absolute risk of HIE is low after TOLAC, infants with severe encephalopathy are at risk of developing long-term neurologic morbidity that can be disabling. (See "Clinical features, diagnosis, and treatment of neonatal encephalopathy", section on 'Prognosis'.)
●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) . 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).
●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 .
Birth trauma from lacerations is more commonly seen in infants born by ERCD.
The intubation rate for meconium-stained amniotic fluid is significantly higher in TOLAC than in ERCD. The rates of suspected and proven neonatal sepsis are also higher for TOLAC than ERCD (suspected sepsis 5 versus 2 percent; proven sepsis 1 versus 0 percent) .
Choosing the route of delivery — Choosing the route of delivery should be a shared decision-making process and, whenever possible, the woman’s preference should be honored [20,26]. However, many patients are insufficiently informed of the complexities of the issues when they make their decision on route of delivery . 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 the American College of Obstetricians and Gynecologists (ACOG) and from the National Library of Medicine (NLM).
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 Queensland Centre for Mothers and Babies.
A Cochrane review found that the use of decision support tools used independently by the patient ultimately made no difference in the type of birth (TOLAC versus ERCD) women planned, but the use of these tools reduced feelings of uncertainty about their decision .
CHOOSING CANDIDATES FOR TOLAC — The paucity of definitive data that are predictive of maternal and fetal outcome from trial of labor after cesarean delivery (TOLAC) makes determining the ideal candidates for a trial of labor a challenge. It is difficult to accurately predict which women will have a successful or unsuccessful TOLAC and there is no test for reliably assessing which uterine scars are likely or unlikely to rupture.
Predicting likelihood of successful TOLAC — A number of predictive models, screening tools, and nomograms have been developed to identify women with a prior cesarean delivery who have a high or low likelihood of successful TOLAC, but none have been proven to be highly useful clinically [20,26,39-42]. Current screening tools use a combination of obstetric factors, such as maternal demographics (age, race, ethnicity, body mass index [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) . 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 . For this reason, the authors do not use any of these models. The use of calculators as part of the process of counseling women about TOLAC is reviewed in detail separately. (See "Use of calculators for predicting successful trial of labor after cesarean delivery".)
Predicting risk of uterine rupture — Ultrasound measurement of either the thickness of the anterior uterine wall or the size of the uterine scar defect has been studied to identify women at increased risk for uterine rupture or dehiscence. However, at present, use of this imaging technique has not been proven clinically useful. (See "Uterine dehiscence and rupture after previous cesarean delivery", section on 'Use of imaging'.)
Recommendations by national organizations — The following links, tables, and references provide recommendations from selected national organizations about appropriate candidates for TOLAC versus elective repeat cesarean delivery (ERCD).
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 [20,26]. 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 . Success rates are higher in patients with additional characteristics, such as a prior vaginal delivery. (See 'Characteristics that increase the probability of successful TOLAC' below.)
Characteristics that increase the probability of successful TOLAC — TOLAC success rates vary among institutions and providers, and are affected by various antepartum, intrapartum, and nonmedical factors (discussed below).
For women who are appropriate candidates for TOLAC (see 'Optimal candidates' above), the highest success rates (over 80 percent) occur in those who:
●Have had a successful vaginal delivery before or after their cesarean
●Present in active spontaneous labor at ≤40 weeks of gestation with an appropriately-sized fetus
●Had their prior cesarean delivery for fetal malpresentation, or another indication that is unlikely to recur
These and additional characteristics that increase the probability of successful TOLAC are discussed in more detail below.
●Nonrecurrent indication for prior cesarean delivery – A nonrecurrent indication for the prior cesarean delivery increases the probability that TOLAC will be successful. 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 [26,45].
●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 successful TOLAC 4.76, 95% CI 4.35-5.26) [45-51].
●Demographic factors – Hispanic, African American, and Asian women are more likely to pursue a TOLAC, but are less likely to have a successful TOLAC when compared with non-Hispanic white women (OR for successful TOLAC for non-Hispanic Caucasians, African Americans, and Hispanics: 1, 0.69, 0.65, respectively) [26,39,45,52-54].
Increasing maternal age, single marital status, and less than 12 years of education are also associated with a reduced likelihood of successful TOLAC [26,45,52,55].
Women over age 35 years are less likely to pursue a TOLAC; those who attempt TOLAC are less likely to have a successful TOLAC and more likely to experience TOLAC-associated complications than younger women .
The likelihood of successful TOLAC increases with increasing maternal height (for each 5 cm maternal height increase the OR for successful TOLAC is 1.33, 95% CI 1.28-1.37) and is lower in obese women (for BMI >30 kg/m2 the OR for successful TOLAC is 0.55, 95% CI 0.51-0.60) [39,45,57].
●Interpregnancy interval more than six months – An interpregnancy interval of more than six months is desirable, as an interval of less than six months is an independent risk factor for both uterine rupture and maternal morbidity during TOLAC. (See "Interpregnancy interval and obstetrical complications".)
●Absence of 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 [45,46,53]. In one prospective study, however, there were no significant differences in the rates of successful TOLAC in women with these medical disorders .
●Spontaneous labor on admission to the labor unit – 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 >4 cm 2.56, 95% CI 2.38-2.67) [26,45].
●Fetal weight less than 4000 grams – A fetus weighing more than 4000 g halves the likelihood of successful TOLAC (successful TOLAC for birth weight >4000 g OR 0.55, 95% CI 0.49-0.61) [26,45,58,59].
●Delivery in a university hospital – University hospitals or those affiliated with an obstetrics and gynecology residency program have higher rates of TOLAC and successful TOLAC [55,59,60]. 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 TOLAC when compared to a tertiary care or perinatal center . As an example, a study that compared successful TOLAC rates across hospital settings in California reported rates of successful TOLAC (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 .
Possibly appropriate candidates — Data regarding risk of uterine rupture in the following situations are more limited and based on sparse or inconsistent scientific evidence . ACOG recommends that after individualized risk assessment and counseling, patients in the following situations be considered candidates for TOLAC .
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) . In contrast, a NICHD Maternal Fetal Medicine Units Network study found significant differences in the rates of uterine rupture during TOLAC by the type of previous hysterotomy incision . 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.
We do not offer TOLAC to women with a prior low vertical uterine incision.
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) . 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.
We do not offer TOLAC to women with two prior low transverse uterine incisions, but our approach is not universal.
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 two large studies 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 [35,64]. As an example, uterine rupture occurred in 0.5 percent of women with an unknown scar type and 0.7 percent of women with a known low transverse incision in the National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network study .
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.
We do not offer TOLAC to women with an unknown uterine incision, but our approach is not universal.
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 [20,44,58,65]. In addition, there are at least two reports that have described a 2 to 3 percent risk of uterine rupture in these women [66,67]. The authors discuss these issues with patients and offer induction of labor by amniotomy at 40 weeks of gestation if the cervix is favorable.
Twin 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 [68-70]. ACOG has opined that women with twin pregnancies and one previous low transverse cesarean delivery are candidates for TOLAC if they have no contraindications to vaginal birth . (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 fetus >4000 g 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 [72-74].
Fetal demise — (See "Fetal demise and stillbirth: Maternal care".)
Inappropriate candidates — Most clinicians believe the risks of TOLAC outweigh the benefits in the following settings :
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 NICHD 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 . 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) .
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 [76-80]. Women in whom the prior rupture involved the upper uterine segment have experienced a repeat rupture rate as high as 32 percent . In a 25-year literature review, 22 women identified to have uterine rupture subsequently became pregnant again . 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  are all at increased risk of scar dehiscence or rupture in subsequent pregnancy, and thus should undergo delivery by ERCD by 37 weeks of gestation. (See "Uterine dehiscence and rupture after previous cesarean delivery".)
Prior uterine dehiscence — In a woman who has experienced a prior uterine scar dehiscence and repair, the likelihood of subsequent uterine rupture with potential catastrophic outcome is unclear. There have been isolated reports of both antepartum and interpregnancy uterine scar repairs followed by successful pregnancies; however, numbers are small and await confirmation on a larger scale. While consensus recommendations for the management of the woman with a prior uterine dehiscence are not available, the authors do not offer TOLAC to these patients and plan delivery by ERCD at 37 weeks of gestation [82,83]. (See "Uterine dehiscence and rupture after previous cesarean delivery", section on 'Recurrence risk and management of future pregnancy'.)
Placenta previa, breech presentation, etc — 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).
MANAGEMENT OF LABOR AND DELIVERY — Intrapartum management of patients undergoing trial of labor after cesarean delivery (TOLAC) is similar to that in patients with an unscarred uterus except they are more closely monitored for signs of uterine rupture, especially when uterotonic agents are administered.
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 American Society of Anesthesiologists (ASA) and the American College of Obstetricians and Gynecologists (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) [17-19].
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 . One antepartum option is referral to another facility with appropriate resources to obtain optimal outcomes. However, some doctors and patients may elect to proceed with TOLAC even if all recommended conditions cannot be met. In all cases, any decision to plan for TOLAC in a setting with lack of immediately available resources should be made only after careful consideration by the woman and her healthcare provider. In such instances, the discussion and plan should be documented in the obstetrical record.
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 . Intrauterine pressure monitoring is unnecessary, as it is an insensitive method for early diagnosis of uterine rupture [84,85].
Labor progress in women with no previous vaginal births should be similar to that in normal nulliparous women, and labor patterns in women who have delivered vaginally are similar to those in multigravidas [86,87].
Induction and augmentation of labor — Some women who plan TOLAC will develop a maternal or fetal indication for delivery before the onset of labor. The benefits and harms of elective repeat cesarean delivery (ERCD) versus induction of labor have not been evaluated by randomized trials . 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 [35,89-91]. 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 [58,92,93]; however, neither induction nor augmentation is strongly contraindicated.
Induction — If the cervix is dilated and favorable, our preference is to perform amniotomy to induce labor. In a practice bulletin, ACOG recognized induction of labor with oxytocin or a mechanical method as options for women undergoing TOLAC . We agree with ACOG and others that misoprostol (prostaglandin E1) should 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 [44,94-97].
Two concerns about inducing labor in women with a prior cesarean delivery 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 or mechanical methods 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".)
Consensus opinion recommends against induction in women with two previous cesareans .
Oxytocin augmentation — Women whose labors do not follow generally accepted standards of labor progress in the active phase should be managed with oxytocin augmentation or repeat cesarean delivery, as appropriate. Despite a paucity of high-quality data, given the relative infrequency with which uterine rupture occurs, ACOG supports use of oxytocin for augmentation of labor in women with a previous cesarean delivery .
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) [35,98,99], and two others did not find an increased risk [100,101]. 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.
It is unclear whether oxytocin regimens should be modified or an upper dose limit should be set in women undergoing TOLAC; this issue has not been evaluated extensively. A case-control study reported an increasing risk of uterine rupture with increasing oxytocin dose; the authors suggested upper limit of 20 mU/min . Another study found the risk of rupture was primarily related to hyperstimulation . The low incidence of uterine rupture limits the power of these studies to detect small differences in dose-related risk of rupture.
Although clinicians generally have a lower threshold for diagnosing failure to progress in women undergoing TOLAC than in women with an unscarred uterus, evidence-based guidance does not exist. Based on expert consensus, the French College of Gynecologists and Obstetricians suggest that the total duration of failure to progress before performing cesarean delivery in the active phase should not exceed three hours .
Clinical findings, diagnosis, and management of uterine rupture — (See "Uterine dehiscence and rupture after previous cesarean delivery".)
Analgesia and anesthesia — Epidural analgesia may be used to provide adequate pain relief during labor . Epidural analgesia does not appear to mask the signs and symptoms of uterine rupture, and/or reduce the chance of successful TOLAC .
Amnioinfusion for management of variable decelerations — In women with an unscarred uterus and variable decelerations during labor, a systematic review of observational studies found that amnioinfusion was associated with a reduction in cesarean delivery and improvement in some neonatal outcomes . The risks of rare, but serious, adverse effects were not measurable. There are even fewer data on amnioinfusion in women undergoing TOLAC [104-107]. Uterine ruptures have been reported in these patients [105-107], but it is unknown whether the rates of rupture and cesarean delivery are different from the rates in women undergoing TOLAC with variable decelerations not treated with amnioinfusion. Given the paucity of safety and efficacy data, the authors and section editors of this topic do not treat variable decelerations with amnioinfusion in women undergoing TOLAC.
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 . There are no data on the value of routine examination to identify asymptomatic uterine dehiscence or whether repair is indicated, but the authors routinely perform uterine exploration following uncomplicated successful TOLAC.
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). The decision regarding mode of delivery is complex, but must be made by each woman after informed discussion with her physician (table 3). 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 9 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 'Risks and benefits of TOLAC and ERCD' above.)
●Successful TOLAC varies upon the clinical situation that led to the first cesarean birth. It is higher in women with a previous successful TOLAC, previous vaginal delivery, previous cesarean delivery for nonvertex presentation, and in 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 particularly poor prognosis. However, there is no completely reliable way to predict which TOLACs will fail. (See 'Characteristics that increase the probability of successful TOLAC' above.)
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