100 YEARS OF CONTROVERSY
FACTORS THAT INFLUENCE A TRIAL OF LABOR
TRIAL OF LABOR VERSUS REPEAT CESAREAN DELIVERY
CANDIDATES FOR A TRIAL OF LABOR
LABOR AND DELIVERY CONSIDERATIONS
COMPLICATIONS WITH MULTIPLE REPEAT CESAREAN DELIVERIES
STATE OF VAGINAL BIRTH AFTER CESAREAN—2014
Once a cesarean, always a cesarean.
Once a cesarean, always a trial of labor?
Once a cesarean, always a controversy.
Few issues in modern obstetrics have been as controversial as the management of the woman who has undergone a prior cesarean delivery. As we approach the 100th anniversary of the oft-quoted remark by Cragin, the issue remains unsettled.
100 YEARS OF CONTROVERSY
Management of the woman who has undergone a previous cesarean delivery has been—for good reasons—a controversial topic for more than 100 years. By the beginning of the 20th century, cesarean delivery had become relatively safe. But, as women survived the first operation and conceived again, they were now at risk for uterine rupture. This was because of the prevailing use of vertical hysterotomy—and especially the classical incision (Williams, 1903). The inherent dangers of uterine rupture led to the dictum above by Edwin B. Cragin (1916). It was not until later that Kerr (1921) described use of a transverse low-segment uterine incision that was predicted to be less likely to rupture with subsequent labor.
Perhaps contrary to popular belief, these events did not result in strict adherence to repeat cesarean delivery. In the 10th edition of Williams Obstetrics, Eastman (1950) stated a preference for vaginal delivery in these women and described a 30-percent vaginal delivery rate at Johns Hopkins Hospital. But while only 2 percent of women who labored had a uterine rupture, they had a 10-percent maternal mortality rate. Subsequent observational studies from the 1960s also suggested that vaginal delivery was a reasonable option (Pauerstein 1966, 1969). Germane to this is that through the 1960s, the overall cesarean delivery rate was only approximately 5 percent. Beginning then, however, well-intentioned efforts to improve perinatal outcomes were accompanied by a rapidly escalating cesarean delivery rate that exceeded 20 percent by 1985 (Chap. 30, p. 587). In addition, the concept of cesarean delivery on maternal request has increased the primary operation rate (American College of Obstetricians and Gynecologists, 2013b). And as expected, as the primary cesarean rate increased, the rate for repeat operations followed (Rosenstein, 2013).
To address this, a National Institutes of Health (NIH) Consensus Development Conference (1981) was convened, and it questioned the necessity of routine repeat cesarean delivery. With support and encouragement from the American College of Obstetricians and Gynecologists (1988, 1994), enthusiastic attempts were begun to increase the use of vaginal birth after cesarean—VBAC. These attempts were highly successful, and VBAC rates increased from 3.4 percent in 1980 to a peak of 28.3 percent in 1996. These rates, along with a concomitant decline in total cesarean delivery rates for the United States, are shown in Figure 31-1.
FIGURE 31-1 Total and primary cesarean delivery (CS) rates and vaginal birth after previous cesarean (VBAC) rate: United States, 1989–2010. Epochs denoted within rectangles represent contemporaneous ongoing events related to these rates. (Data from National Institutes of Health: NIH Consensus Development Conference, 2010; Martin, 2012a,b).
As the vaginal delivery rate increased, so did reports of uterine rupture-related maternal and perinatal morbidity and mortality (McMahon, 1996; Sachs, 1999). These dampened prevailing enthusiasm for a trial of labor and stimulated the American College of Obstetricians and Gynecologists (1998) to caution that such trials should be attempted only in appropriately equipped institutions with physicians readily available to provide emergency care. Less than a year later, the College (1999) recommended that physicians should be immediately available. Many believe that this one-word change—from readily to immediately available—was in large part responsible for the decade-long decline in national VBAC rates illustrated in Figure 31-1 (Cheng, 2014; Leeman, 2013). The VBAC rate leveled at approximately 8 percent by 2009 and 2010, while the total cesarean delivery rate increased to 32.8 percent in 2011 (Martin, 2011, 2012a,b). Because the success rate of a trial of labor resulting in a VBAC is not 100 percent, another way of examining these changes was described by Uddin and colleagues (2013). These investigators reported the proportion of women with a prior cesarean delivery who underwent a trial of labor. This number peaked in 1997, when slightly more than half of all of these women chose a trial of labor. Thereafter, this percentage plummeted and reached a nadir of about 16 percent in 2005. Since that time, the proportion has increased and averaged 20 to 25 percent through 2009. Ironically, during this same decade, there were continuing reports that described the success and safety of VBAC in selected clinical settings.
In reality, there are several other interrelated factors—both medical and nonmedical—that have undoubtedly contributed to declining VBAC rates. Because of their complexity and importance, the Eunice Kennedy ShriverNational Institute of Child Health and Human Development (NICHD) and the Office of Medical Applications of Research (OMAR) convened a National Institutes of Health Consensus Development Conference Panel (2010) to study these issues. The Panel report included a contemporaneous summary concerning the risks and benefits of repeat cesarean versus vaginal delivery. These findings are subsequently described along with summaries of current recommendations by various professional organizations. However, data from California indicate that VBAC rates have not perceptibly increased since the 2010 NIH Consensus Conference that encouraged greater access to a trial of labor after cesarean delivery (Barger, 2013).
FACTORS THAT INFLUENCE A TRIAL OF LABOR
Delivery planning for the woman who has had a previous cesarean delivery can begin with preconceptional counseling, but should definitely be addressed early in prenatal care. Importantly, any decision arrived at is subject to continuing revisions as dictated by exigencies that arise during the course of pregnancy. Assuming no mitigating circumstances, there are two basic choices. First is a trial of labor after cesarean (TOLAC) with the goal of achieving VBAC. If cesarean delivery becomes necessary during the trial, then it is termed a “failed trial of labor.” A second choice is elective repeat cesarean delivery (ERCD). This includes scheduled cesarean delivery as well as unscheduled but planned cesarean delivery for spontaneous labor or another indication.
Selection should consider factors known to influence a successful trial of labor as well as benefits and risks. In general, appropriately selected women who attempt VBAC have success rates that approximate 75 percent. These rates vary between institutions and providers and are affected by prepregnancy, antepartum, intrapartum, and nonmedical factors.
Some medical variables that influence a successful trial of labor are listed in Table 31-1. As for economical and medicolegal factors, professional liability concerns and insufficient resources to provide adequate staffing for hospitals to accommodate a trial of labor weigh heavily.
TABLE 31-1. Some Factors That Influence a Successful Trial of Labor in a Woman with Prior Cesarean Delivery
TRIAL OF LABOR VERSUS REPEAT CESAREAN DELIVERY
As evidence mounted that the risk of uterine rupture and perinatal morbidity and mortality might be greater than expected, the American College of Obstetricians and Gynecologists (1988, 1998, 1999, 2013a) issued updated Practice Bulletins supporting labor trials but also urging a more cautious approach. It is problematic that both options have risks and benefits to mother and fetus but that these are not always congruent.
Uterine rupture and its associated complications clearly are increased with a trial of labor. It is this increased risk that underpins most of the angst in attempting a trial of labor. Despite this, some have argued that these factors should weigh only minimally in the decision to attempt a trial because their absolute risk is low. One of the largest and most comprehensive studies designed to examine risks associated with vaginal birth in women with a prior cesarean delivery was conducted by the Maternal-Fetal Medicine Units (MFMU) Network (Landon, 2004). In this prospective study conducted at 19 academic medical centers, the outcomes of nearly 18,000 women who attempted a trial of labor were compared with those of more than 15,000 women who underwent elective repeat cesarean delivery. As shown in Table 31-2, although the risk of uterine rupture was higher among women undergoing a trial of labor, the absolute risk was small—only 7 per 1000. To the contrary, however, there were no uterine ruptures in the elective cesarean delivery group. Not surprisingly, rates of stillbirth and hypoxic ischemic encephalopathy were significantly greater in the trial of labor arm. Others have reported similar results (Chauhan, 2003; Mozurkewich, 2000). In one study of nearly 25,000 women with a prior cesarean delivery, perinatal death risk was 1.3 per 1000 among the 15,515 women who had a trial of labor (Smith, 2002). Although the absolute risk is small, it is 11 times greater than the risk found in 9014 women with a planned repeat cesarean delivery.
TABLE 31-2. Complications in Women with a Prior Cesarean Delivery Enrolled in the NICHD Maternal-Fetal Medicine Units Network, 1999–2002
Most studies suggest that the maternal mortality rate does not differ significantly between women undergoing a trial of labor compared with those undergoing an elective repeat cesarean delivery (Landon, 2004; Mozurkewich, 2000). One outlier was a retrospective cohort study of more than 300,000 Canadian women with a prior cesarean delivery (Wen, 2005). In this study, the maternal death rate for women undergoing an elective repeat cesarean delivery was 5.6 per 100,000 compared with 1.6 per 100,000 for those having a trial of labor.
Estimates of maternal morbidity have also produced conflicting results. In the metaanalysis by Mozurkewich and Hutton (2000), women undergoing a trial of labor were approximately half as likely to require a blood transfusion or hysterectomy compared with those undergoing repeat cesarean delivery. Conversely, in the MFMU Network study, Landon and coworkers (2004) observed that the risks of transfusion and infection were significantly greater for women attempting a trial of labor (see Table 31-2). Rossi and D’Addario (2008) reported similar findings in their metaanalysis. McMahon and associates (1996), in a population-based study of 6138 women, found that major complications—hysterectomy, uterine rupture, or operative injury—were almost twice as common in women undergoing a trial of labor compared with those undergoing an elective cesarean delivery. Importantly, compared with a successful trial of labor, the risk of these major complications was fivefold greater in women whose attempted vaginal delivery failed. The metaanalysis cited above also reported an increased incidence of overall maternal complications when women with a failed vaginal delivery were compared with those undergoing successful vaginal delivery—17 versus 3 percent, respectively (Rossi, 2008). Similar findings have been reported from the Network Cesarean Registry (Babbar, 2013).
Fetal and Neonatal Risks
The Panel found little or no evidence regarding short- and long-term neonatal outcomes after TOLAC versus ERCD. Most of the available evidence documents differences comparing actual rather than intended mode of delivery and is of low quality. A trial of labor is associated with significantly higher perinatal mortality rates compared with ERCD—perinatal mortality rate 0.13 versus 0.05 percent; neonatal mortality rate 0.11 versus 0.06 (Guise, 2010). A trial of labor also appears to be associated with a higher risk of hypoxic ischemic encephalopathy (HIE) than ERCD. The Maternal-Fetal Medicine Networks Unit study reported the incidence of HIE at term to be 46 per 100,000 trials of labor compared with zero cases in women undergoing ERCD (Landon, 2004).
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 (Guise, 2010). But, 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. Finally, there are no significant differences in 5-minute Apgar scores or neonatal intensive care unit admissionsfor infants delivered by TOLAC compared with those delivered by ERCD. Birth trauma from lacerations is more commonly seen in infants born by ERCD.
Maternal versus Fetal Risks
Relative risks for mother and baby differ between modes of delivery. Regarding overall risks, the Panel (2010) concluded that 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. In comparison, 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.
Despite potential concerns of increased complications, an elective repeat cesarean delivery is considered by many women to be preferable to a trial of labor. Frequent reasons include the convenience of a scheduled delivery and the fear of a prolonged and potentially dangerous labor. In an earlier study, Abitbol and colleagues (1993) found that these preferences persisted despite extensive antepartum counseling.
CANDIDATES FOR A TRIAL OF LABOR
There are few high-quality data available to guide selection of trial of labor candidates (Guise, 2004; Hashima, 2004). That said, having fewer complicating risk factors increases the likelihood of success (Gregory, 2008). Several algorithms and nomograms have been developed to aid prediction, but none has demonstrated reasonable prognostic value (Grobman, 2007b, 2008, 2009; Macones, 2006; Metz, 2013; Srinivas, 2007). Use of a predictive model for failed trial of labor, however, was found to be somewhat predictive of uterine rupture or dehiscence (Stanhope, 2013). Despite these limitations for precision, several points are pertinent to the evaluation of these women and are described in the next sections. Current recommendations of the American College of Obstetricians and Gynecologists (2013a) are that most women with one previous cesarean delivery with a low-transverse hysterotomy are candidates, and if appropriate, they should be counseled regarding a trial of labor versus elective repeat cesarean delivery.
Prior Uterine Incision
Prior Incision Type
The type and number of prior cesarean deliveries are overriding factors in recommending a trial of labor. Women with one prior low-transverse hysterotomy have the lowest risk of symptomatic scar separation (Table 31-3). The highest risks are with prior vertical incisions extending into the fundus, such as the classical incision shown in Figure 31-2 (Society for Maternal Fetal Medicine, 2013). Importantly, in some women, the classical scar will rupture before the onset of labor, and this can happen several weeks before term. In a review of 157 women with a prior classical cesarean delivery, one woman had a complete uterine rupture before the onset of labor, whereas 9 percent had a uterine dehiscence (Chauhan, 2002).
TABLE 31-3. Types of Prior Uterine Incisions and Estimated Risks for Uterine Rupture
FIGURE 31-2 Ruptured vertical cesarean section scar (arrow) identified at time of repeat cesarean delivery early in labor. The two black asterisks to the left indicate some sites of densely adhered omentum.
The risk of uterine rupture in women with a prior vertical incision that did not extend into the fundus is unclear. Martin (1997) and Shipp (1999) and their coworkers reported that these low-vertical uterine incisions did not have an increased risk for rupture compared with low-transverse incisions. The American College of Obstetricians and Gynecologists (2013a) concluded that although there is limited evidence, women with a prior vertical incision in the lower uterine segment without fundal extension may be candidates for a trial of labor. This is in contrast to prior classical or T-shaped uterine incisions, which are considered by most as contraindications to labor.
Currently, there are few indications for a primary vertical incision (Osmundson, 2013). In those instances—for example, preterm breech fetus with an undeveloped lower segment—the “low vertical” incision almost invariably extends into the active segment. It is not known, however, how far upward the incision has to extend before risks become those of a true classical incision. It is helpful in the operative report to document its exact extent.
Prior preterm cesarean delivery may have an increased risk for rupture. Although the type of prior incision was not known, Sciscione and associates (2008) reported that women who had a prior preterm cesarean delivery were twice as likely to suffer a uterine rupture compared with those with a prior term cesarean delivery. This may be in part explained by the increased likelihood with a preterm fetus of extension of the uterine incision into the contractile portion. Conversely, Harper and colleagues (2009) did not find a significantly increased rate of rupture during subsequent VBAC in women with a prior cesarean delivery performed at or before 34 weeks.
There are special considerations for women with uterine malformations who have undergone cesarean delivery. Earlier reports suggested that the uterine rupture risk in a subsequent pregnancy was increased compared with the risk in those with a prior low-transverse hysterotomy and normally formed uterus (Ravasia, 1999). But, in a study of 103 women with müllerian duct anomalies who had one prior cesarean delivery and who attempted a trial of labor, there were no cases of uterine rupture (Erez, 2007). Given the wide range of risk for uterine rupture associated with the various uterine incision types, it is not surprising that most fellows of the American College of Obstetricians and Gynecologists consider the type of prior incision to be the most important factor when considering a trial of labor (Coleman, 2005).
Prior Incision Closure
As discussed in Chapter 30 (p. 596), the low-transverse hysterotomy incision can be sutured in either one or two layers. Whether the risk of subsequent uterine rupture is affected by these is unclear. Chapman (1997) and Tucker (1993) and their associates found no relationship between a one- and two-layer closure and the risk of subsequent uterine rupture. And although Durnwald and Mercer (2003) also found no increased risk of rupture, they reported that uterine dehiscence was more common after single-layer closure. In contrast, Bujold and coworkers (2002) found that a single-layer closure was associated with nearly a fourfold increased risk of rupture compared with a double-layer closure. In response, Vidaeff and Lucas (2003) argued that experimental models have not demonstrated advantages of a double-layer closure and that the evidence is insufficient to routinely recommend a double-layer closure. At Parkland Hospital we routinely suture the low-segment incision with one running locking suture.
Number of Prior Cesarean Incisions
There are at least three studies that reported a doubling of the rupture rate—from approximately 0.6 to 1.85 percent—in women with two versus one prior transverse hysterotomy incision (Macones, 2005a; Miller, 1994; Tahseen, 2010). In contrast, analysis of the MFMU Network database by Landon and colleagues (2006) did not confirm this. Instead, they reported an insignificant difference in the uterine rupture rate in 975 women with multiple prior cesarean deliveries compared with 16,915 women with a single prior operation—0.9 versus 0.7 percent, respectively. As discussed subsequently, other serious maternal morbidity increases along with the number of prior cesarean deliveries (Marshall, 2011).
Imaging of Prior Incision
Sonographic measurement of a prior hysterotomy incision has been used to predict the likelihood of rupture with a trial of labor. Large defects in the hysterotomy scar in a nonpregnant uterus forecast a greater risk for rupture (Osser, 2011). Naji and associates (2013a,b) found that the residual myometrial thickness decreased as pregnancy progressed and that rupture correlates with a thinner scar. From their review, however, Jastrow and coworkers (2010) found no ideal thickness to be suitably predictive. The optimal safe threshold value for the lower uterine segment—smallest measurement from amnionic fluid to bladder—ranged from 2.0 to 3.5 mm. For the myometrial layer—smallest measurement of the hypoechoic portion of the lower segment, it was 1.4 to 2.0 mm. With a lower segment < 2.0 mm, the risk of uterine rupture was increased 11-fold. With myometrial thickness < 1.4 mm, uterine rupture was increased fivefold. The measurements, however, are not predictive for an individual woman (Bergeron, 2009).
Prior Uterine Rupture
Women who have previously sustained a uterine rupture are at increased risk for recurrence during a subsequent attempted VBAC. As shown in Table 31-3, those with a previous low-segment rupture have a 2- to 6-percent recurrence risk, whereas prior upper segment uterine rupture confers a 9- to 32-percent risk (Reyes-Ceja, 1969; Ritchie, 1971). We believe that women with a prior uterine rupture or classical or T-shaped incision ideally should undergo repeat cesarean delivery when fetal pulmonary maturity is assured, and preferably before the onset of labor. They should also be counseled regarding the hazards of unattended labor and signs of possible uterine rupture.
Magnetic resonance imaging studies of myometrial healing suggest that complete uterine involution and restoration of anatomy may require at least 6 months (Dicle, 1997). To explore this further, Shipp and colleagues (2001) examined the relationship between interdelivery interval and uterine rupture in 2409 women who had one prior cesarean delivery. There were 29 women with a uterine rupture—1.4 percent. Interdelivery intervals of ≤ 18 months were associated with a threefold increased risk of symptomatic rupture during a subsequent trial of labor compared with intervals > 18 months. Similarly, Stamilio and coworkers (2007) noted a threefold increased risk of uterine rupture in women with an interpregnancy interval of < 6 months compared with one ≥ 6 months. But they also reported that interpregnancy intervals of 6 to 18 months did not significantly increase the risk.
Prior Vaginal Delivery
Prior vaginal delivery, either before or after a cesarean birth, significantly improves the prognosis for a subsequent vaginal delivery with either spontaneous or induced labor (Grinstead, 2004; Hendler, 2004; Mercer, 2008). Prior vaginal delivery also lowers the risk of subsequent uterine rupture and other morbidities (Cahill, 2006; Hochler, 2014; Zelop, 2000). Indeed, the most favorable prognostic factor is prior vaginal delivery.
Indication for Prior Cesarean Delivery
Considering all women who elect trial of labor, 60 to 80 percent will have a successful vaginal delivery (American College of Obstetricians and Gynecologists, 2013a). Women with a nonrecurring indication—for example, breech presentation—have the highest success rate of nearly 90 percent (Wing, 1999). Those with a prior cesarean delivery for fetal compromise have an approximately 80-percent success rate, and for those done for labor arrest, success rates approximate 60 percent (Bujold, 2001; Peaceman, 2006). Prior second-stage cesarean delivery can be associated with second-stage uterine rupture in a subsequent pregnancy (Jastrow, 2013).
Most studies show that increasing fetal size is inversely related to successful trial of labor. The risk for uterine rupture is less robust. Zelop and associates (2001) compared the outcomes of almost 2750 women undergoing a trial of labor, and 1.1 percent had a uterine rupture. The rate increased—albeit not significantly—with increasing fetal weight. The rate was 1.0 percent for fetal weight < 4000 g, 1.6 percent for > 4000 g, and 2.4 percent for > 4250 g. Similarly, Elkousy and colleagues (2003) reported that the relative risk of rupture doubled if birthweight was > 4000 g. Conversely, Baron and coworkers (2013a) did not find increased uterine rupture with birthweights > 4000 g.
Fetal size at the opposite end of the spectrum may increase the chances of a successful VBAC. Specifically, women who attempt a trial of labor with a preterm fetus have higher successful VBAC rates and lower rupture rates (Durnwald, 2006; Quiñones, 2005).
Perhaps surprisingly, twin pregnancy does not appear to increase the uterine rupture risk with trial of labor. Ford and associates (2006) analyzed the outcomes of 1850 such women and reported a 45-percent successful vaginal delivery rate and a rupture rate of 0.9 percent. Similar studies by Cahill (2005) and Varner (2007) and their colleagues reported rupture rates of 0.7 to 1.1 percent and vaginal delivery rates of 75 to 85 percent. According to the American College of Obstetricians and Gynecologists (2013a), women with twins and a prior low-transverse hysterotomy who are otherwise candidates for vaginal delivery can safely undergo a trial of labor.
Obesity decreases the success rate of trial of labor. Hibbard and coworkers (2006) reported the following vaginal delivery rates: 85 percent with a normal body mass index (BMI), 78 percent with a BMI between 25 and 30, 70 percent with a BMI between 30 and 40, and 61 percent with a BMI of 40 or greater. Similar findings were reported by Juhasz and associates (2005).
Most women with a prior cesarean delivery and fetal death in the current pregnancy would prefer a VBAC. Although fetal concerns are obviated, available data suggest that maternal risks are increased. Nearly 46,000 women with a prior cesarean delivery in the Network database had a total of 209 fetal deaths (Ramirez, 2010). There were 76 percent who had a trial of labor with a success rate of 87 percent. Overall, the rupture rate was 2.4 percent. Four of five ruptures were during induction in 116 women with one prior transverse incision—3.4 percent.
LABOR AND DELIVERY CONSIDERATIONS
If elective repeat cesarean delivery is planned, it is essential that the fetus be mature. As shown in Figure 31-3, significant and appreciable adverse neonatal morbidity has been reported with elective delivery before 39 completed weeks (Chiossi, 2013; Clark, 2009; Tita, 2009). The American Academy of Pediatrics and the American College of Obstetricians and Gynecologists (2012) have established the following guidelines for timing an elective operation, and at least one of these three must be documented:
1. Ultrasound measurement < 20 weeks supports a gestational age of ≥ 39 weeks.
2. Fetal heart sounds have been documented for 30 weeks by Doppler ultrasound.
3. A positive serum or urine β-hCG test result has been documented for ≥ 36 weeks.
FIGURE 31-3 Neonatal morbidity and mortality rates seen with 13,258 elective repeat cesarean deliveries. Any adverse outcome includes death. Sepsis includes suspected and proven. RDS = respiratory distress syndrome; TTN = transient tachypnea of the newborn. (From Tita, 2009.)
Accurate gestational dating is suitable using any of the above criteria. Other options are to await spontaneous labor or to document fetal pulmonary maturation by amnionic-fluid analysis (Chap. 34, p. 655).
The risks and benefits of a trial of labor versus a repeat cesarean delivery should be thoroughly discussed, and the decision to attempt a trial of labor is made by the informed woman in conjunction with her health-care provider (American Academy of Pediatrics and the American College of Obstetricians and Gynecologists, 2012). As previously emphasized, no woman with a prior uterine incision should be forced to undergo a trial of labor.
Because of the risks of uterine rupture for women undergoing a trial of labor, the American Academy of Pediatricians and the American College of Obstetricians and Gynecologists (2012) recommend that such trials be undertaken only in facilities with staff immediately available to provide emergency care. Moreover, these centers should have a plan for managing uterine rupture.
Some argue that these provisions deny women full access to choices. For example in an earlier survey of Ohio hospitals, 15 percent of Level I, 63 percent of Level II, and 100 percent of Level III institutions met these requirements (Lavin, 2002). Moreover, an obstetrical anesthesia workforce survey reported that these rules were in place in 86 percent of hospitals with ≥ 1500 annual deliveries, in 45 percent of those with 500 to 1499 deliveries, and in 33 percent of those with < 500 deliveries.
Cervical Ripening and Labor Stimulation
As discussed, labor induction is associated with a higher failure rate for a trial of labor. The risks for uterine rupture, however, are less clear with induction or augmentation, with the exception of prostaglandin E1—misoprostol—which is contraindicated (American College of Obstetricians and Gynecologists, 2013a; Ophir, 2012). While most institutions are not so conservative, we do not induce or augment labor pharmacologically in these women at Parkland Hospital. Instead, we attempt induction by amniotomy. Other considerations are to avoid induction or augmentation in women with an unknown prior incision type, an unfavorable cervix, or pregnancy > 40 weeks.
Induction or augmentation of labor with oxytocin has been implicated in increased rates of uterine rupture in some studies (Zelop, 1999). In the Network study reported by Landon and colleagues (2004), uterine rupture was more frequent in women induced—1.1 percent—than in those in spontaneous labor—0.4 percent. Among women in this trial who had never had a prior vaginal delivery, the uterine rupture risk associated with an oxytocin induction was 1.8 percent—a fourfold increased risk compared with spontaneous labor (Grobman, 2007a). In contrast, in one case-control study, induction was not associated with a higher risk for rupture (Harper, 2012a). In an observational study, the success rate of induction was 67 percent (Shatz, 2012).
Cahill and coworkers (2008) reported a dose-related risk of rupture with oxytocin. At an infusion dose of 21 to 30 mU/min, the uterine rupture risk was fourfold greater than that in women not given oxytocin. Goetzl and associates (2001) described similar findings. They concluded, however, that differences in the dose or patterns of oxytocin use associated with uterine rupture were not substantive enough to require development of different induction protocols.
Various prostaglandin preparations that are commonly employed for cervical ripening or labor induction are discussed in Chapter 26 (p. 526). Safety with their use in women with a prior cesarean delivery is not clear because of conflicting data. For example, Wing and colleagues (1998) described a comparative study of PGE1—misoprostol—versus oxytocin for labor induction in women with a prior cesarean delivery. They terminated their trial after two of the first 17 women assigned to misoprostol developed a uterine rupture. Other studies confirmed this, and most consider misoprostol to be contraindicated (American College of Obstetricians and Gynecologists, 2013a).
Studies to evaluate other prostaglandins for induction have mixed results. Ravasia and coworkers (2000) compared uterine rupture in 172 women given PGE2 gel with 1544 women in spontaneous labor. The rupture rate was significantly greater in women treated with PGE2 gel—2.9 percent—compared with 0.9 percent in those with spontaneous labor. Lydon-Rochelle and associates (2001) also reported that induction with prostaglandins for a trial of labor increased the uterine rupture risk.
Not all studies report an increased risk of uterine rupture with prostaglandins. In the Network study cited previously, there was a uterine rupture rate of 1.4 percent when any prostaglandin was used in combination with oxytocin (Landon, 2004). But in the subgroup of 227 women in whom labor was induced with a prostaglandin only, there were no ruptures. Similar findings were reported in that intravaginal prostaglandins were not found to be associated with an increased uterine rupture risk (Macones, 2005b). These latter investigators, along with Kayani and colleagues (2005), found that sequential use of a prostaglandin followed by oxytocin was associated with a threefold-increased risk of rupture compared with spontaneous labor.
After reviewing these more contemporaneous reports, the American College of Obstetricians and Gynecologists (2013a) concluded that labor induction for some women who attempt a trial of labor is a reasonable option. The College also concluded that it is reasonable to (1) avoid misoprostol, (2) select women most likely to have a successful trial of labor, and (3) avoid sequential use of prostaglandins and oxytocin.
Concerns that epidural analgesia for labor might mask the pain of uterine rupture have not been verified. Fewer than 10 percent of women with scar separation experience pain and bleeding, and fetal heart rate decelerations are the most likely sign of rupture (Kieser, 2002). That said, Cahill and coworkers (2010a) documented that more frequent episodes of epidural dosing were associated with increasing uterine rupture rates. Successful VBAC rates are similar, and in some cases higher, among women with labor epidural analgesia compared with those using other forms of analgesia (Landon, 2005). Perhaps related, almost a fourth of successful VBAC deliveries were completed with either forceps or vacuum (Inbar, 2013). The American Academy of Pediatrics and the American College of Obstetricians and Gynecologists (2012) have concluded that epidural analgesia may safely be used during a trial of labor.
Uterine Scar Exploration
Some clinicians routinely document the integrity of a prior scar by placing a hand through the dilated cervix and along the inner surface of the lower uterine segment following successful vaginal delivery. However, routine uterine exploration is considered by others to be unnecessary. Currently, the benefits of scar evaluation in the asymptomatic woman are unclear. There is general agreement, however, that surgical correction of a scar dehiscence is necessary only if significant bleeding is encountered. Our practice is to routinely examine these prior incision sites. Any decision for laparotomy and repair takes into consideration the extent of the tear, whether the peritoneal cavity has been entered, and the presence of active bleeding.
External Cephalic Version
External cephalic version for breech presentation is acceptable in women with a prior cesarean delivery who are contemplating a trial of labor (American College of Obstetricians and Gynecologists, 2013a). This procedure is addressed in Chapter 28 (p. 570).
Uterine rupture typically is classified as either (1) complete when all layers of the uterine wall are separated, or (2) incomplete when the uterine muscle is separated but the visceral peritoneum is intact. Incomplete rupture is also commonly referred to as uterine dehiscence. As expected, morbidity and mortality rates are appreciably greater when rupture is complete. The greatest risk factor for either form of rupture is prior cesarean delivery. In a review of all uterine rupture cases in Nova Scotia between 1988 and 1997, Kieser and Baskett (2002) reported that 92 percent were in women with a prior cesarean birth. Holmgren and associates (2012) described 42 cases of rupture in women with a prior hysterotomy. Of these, 36 were in labor at the time of rupture.
Progress of labor in women attempting VBAC is similar to regular labor, and there is no specific pattern that presages uterine rupture (Graseck, 2012; Harper, 2012b). Before hypovolemic shock develops, symptoms and physical findings in women with uterine rupture may appear bizarre unless the possibility is kept in mind. For example, hemoperitoneum from a ruptured uterus may result in diaphragmatic irritation with pain referred to the chest—directing one to a diagnosis of pulmonary or amnionic fluid embolism instead of uterine rupture. The most common sign of uterine rupture is a nonreassuring fetal heart rate pattern with variable heart rate decelerations that may evolve into late decelerations and bradycardia as shown in Figure 31-4 (American Academy of Pediatrics and American College of Obstetricians and Gynecologists, 2012). In 36 cases of such rupture during a trial of labor, there were fetal signs in 24, maternal in eight, and both in three (Holmgren, 2012). Few women experience cessation of contractions following uterine rupture, and the use of intrauterine pressure catheters has not been shown to assist reliably in the diagnosis (Rodriguez, 1989).
FIGURE 31-4 Fetal heart rate tracing in a woman whose uterus ruptured during labor while pushing. The rupture apparently stimulated a reflex push, after which uterine tone diminished and fetal bradycardia worsened.
In some women, the appearance of uterine rupture is identical to that of placental abruption. In most, however, there is remarkably little appreciable pain or tenderness. Also, because most women in labor are treated for discomfort with either narcotics or epidural analgesia, pain and tenderness may not be readily apparent. The condition usually becomes evident because of fetal distress signs and occasionally because of maternal hypovolemia from concealed hemorrhage.
If the fetal presenting part has entered the pelvis with labor, loss of station may be detected by pelvic examination. If the fetus is partly or totally extruded from the uterine rupture site, abdominal palpation or vaginal examination may be helpful to identify the presenting part, which will have moved away from the pelvic inlet. A firm contracted uterus may at times be felt alongside the fetus.
With rupture and expulsion of the fetus into the peritoneal cavity, the chances for intact fetal survival are dismal, and reported mortality rates range from 50 to 75 percent. Fetal condition depends on the degree to which the placental implantation remains intact, although this can change within minutes. With rupture, the only chance of fetal survival is afforded by immediate delivery—most often by laparotomy—otherwise, hypoxia is inevitable. If rupture is followed by immediate total placental separation, then very few intact fetuses will be salvaged. Thus, even in the best of circumstances, fetal salvage will be impaired. The Utah experiences are instructive here (Holmgren, 2012). Of the 35 laboring patients with a uterine rupture, the decision-to-delivery time was < 18 minutes in 17, and none of these infants had an adverse neurological outcome. Of the 18 born > 18 minutes from decision time, the three infants with long-term neurological impairments were delivered at 31, 40, and 42 minutes. There were no deaths, thus severe neonatal neurological morbidity developed in 8 percent of these 35 women with uterine rupture.
In a study using the Swedish Birth Registry, Kaczmarczyk and colleagues (2007) found that the risk of neonatal death following uterine rupture was 5 percent—a 60-fold increase in risk compared with pregnancies not complicated by uterine rupture. In the Network study, seven of the 114 uterine ruptures—6 percent—associated with a trial of labor were complicated by the development of neonatal hypoxic ischemic encephalopathy (Spong, 2007).
Maternal deaths from rupture are uncommon. For example, of 2.5 million women who gave birth in Canada between 1991 and 2001, there were 1898 cases of uterine rupture, and four of these—0.2 percent—resulted in maternal death (Wen, 2005). In other regions of the world, however, maternal mortality rates associated with uterine rupture are much higher. In a report from rural India, for example, the maternal mortality rate associated with uterine rupture was 30 percent (Chatterjee, 2007).
Hysterectomy versus Repair
With complete rupture during a trial of labor, hysterectomy may be required. In the reports by McMahon (1996) and Miller (1997) and their coworkers, 10 to 20 percent of such women required hysterectomy for hemostasis. In selected cases, however, suture repair with uterine preservation may be performed. Sheth (1968) described outcomes from a series of 66 women in whom repair of a uterine rupture was elected rather than hysterectomy. In 25 instances, the repair was accompanied by tubal sterilization. Thirteen of the 41 mothers who did not have tubal sterilization had a total of 21 subsequent pregnancies. Uterine rupture recurred in four of these—approximately 25 percent. Usta and associates (2007) identified 37 women with a prior complete uterine rupture delivered during a 25-year period in Lebanon. Hysterectomy was performed in 11, and in the remaining 26 women, the rupture was repaired. Twelve of these women had 24 subsequent pregnancies, one third of which were complicated by recurrent uterine rupture. In another study, however, women with a uterine dehiscence were not more likely to have uterine rupture with a subsequent pregnancy (Baron, 2013b).
COMPLICATIONS WITH MULTIPLE REPEAT CESAREAN DELIVERIES
Because of the concerns with attempting a trial of labor—even in the woman with excellent criteria that forecast successful VBAC—most women in the United States undergo elective repeat cesarean delivery. This choice is not without several significant maternal complications, and rates of these increase in women who have multiple repeat operations. The incidences of some common complications for women with one prior transverse cesarean delivery who undergo an elective repeat cesarean delivery were shown in Table 31-2. Finally, half of cesarean hysterectomies done at Parkland Hospital are in women with one or more prior cesarean deliveries (Hernandez, 2013).
The Network addressed issues of increased morbidity in a cohort of 30,132 women who had from one to six repeat cesarean deliveries (Silver, 2006). This report addressed a list of morbidities, most of which increased as a trend with increasing number of repeat operations. The rates of some of the more common or serious complications are depicted in Figure 31-5. In addition to the ones shown, rates of bowel or bladder injury, admission to an intensive care unit or ventilator therapy, and maternal mortality, as well as operative and hospitalization length, showed significantly increasing trends. Similar results have been reported by others (Nisenblat, 2006; Usta, 2005). More difficult to quantify are risks for bowel obstructions and pelvic pain from peritoneal adhesive disease, both of which increase with each successive cesarean delivery (Andolf, 2010; Mankuta, 2013).
FIGURE 31-5 Maternal-Fetal Medicine Units Network: rates of some complications with increasing number of repeat cesarean deliveries. (Data from Silver, 2006.)
Cook and colleagues (2013) from the United Kingdom Obstetric Surveillance System (UKOSS) described adverse sequelae of women with multiple cesarean deliveries. Outcomes of those undergoing a fifth or greater operation were compared with those from women having a second through fourth procedure. Those having five or more cesarean deliveries had significantly increased rates of morbidity compared with rates in women having fewer than five procedures. Specifically, the major hemorrhage rate increased 18-fold; visceral damage, 17-fold; critical care admissions, 15-fold; and delivery < 37 weeks, sixfold. Much of this morbidity was in the 18 percent who had placenta previa or accrete syndromes (Chap. 41, p. 799). A percreta may invade the bladder or other adjacent structures. With this, difficult resection carries an inordinately high risk of hysterectomy, massive hemorrhage with transfusion, and maternal mortality.
STATE OF VAGINAL BIRTH AFTER CESAREAN—2014
The “best answer” for a given woman with a prior cesarean delivery is unknown. We agree with Scott (2011) regarding a “common-sense” approach. Thus, the woman—and her partner if she wishes—are encouraged to actively participate with her health-care provider in the final decision after appropriate counseling. For women who wish TOLAC despite a factor that increases their specific risk, additions to the consent form are recommended (American College of Obstetricians and Gynecologists, 2013a). Bonanno and colleagues (2011) have provided such an example.
Brief synopses of professional society guidelines are shown in Table 31-4. Guidelines that tend to be more conservative are shown in Table 31-5.
TABLE 31-4. Some Recommendations of Professional Societies Concerning a Trial of Labor to Attempt VBAC
TABLE 31-5. Conservative Guidelines to Approach a Trial of Labor Following Cesarean Delivery
Follow ACOG practice guidelines
Education and counseling
Provide ACOG patient pamphlet
Early during prenatal care
Develop preliminary plan
Revisit at least each trimester
Be willing to alter decision
Have facilities availability
Review previous operative note(s)
Review relative and absolute contraindications
Reconsider risks as pregnancy progresses
Tread carefully: > 1 prior transverse CD, unknown incision, twins, macrosomia
Labor and delivery
Cautions for induction—unfavorable cervix, high station
Respect oxytocin—know when to quit
Beware of abnormal labor progress
Respect EFM pattern abnormalities
Know when to abandon a trial of labor
ACOG = American College of Obstetricians and Gynecologists; AROM = artificial rupture of membranes; CD = cesarean delivery; EFM = electronic fetal monitoring.
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