Prior Cesarean Delivery
BS. Nguyễn Hồng Anh
By the beginning of the 20th century, cesarean delivery had become a relatively safe procedure. However, rupture of the uterine scar with subsequent labor was appreciated early. This danger resulted in the ot-quoted remark by Cragin (1916) that “Once a cesarean, always a cesarean.” During the intervening 50 years, enthusiasm developed to allow many of these women to be delivered vaginally. But, as chronicled next, this support has waned during the past three decades. So, as we reach the 100-year mark of Cragin’s pronouncement, the issue remains largely unsettled.
100 YEARS OF CONTROVERSY
Despite Cragin’s early philosophy, some practitioners did allow labor in a subsequent pregnancy after a cesarean delivery. Eastman (1950) described a 30-percent postcesarean vaginal delivery rate at Johns Hopkins Hospital. He also reported a 2-percent uterine rupture rate and associated 10-percent maternal mortality rate. As modern techniques made cesarean delivery safer, observational studies during the 1960s suggested that postcesarean vaginal delivery was a reasonable option (Pauerstein, 1966, 1969). Germane to this is that through the 1960s, the overall cesarean delivery rate approximated only 5 percent. Since then, as the primary cesarean rate has escalated, the repeat cesarean delivery rate followed (Rosenstein, 2013).
During the 1980s, a National Institutes of Health (NIH) Consensus Development Conference on Vaginal Birth After Cesarean (1981) was convened, and the participants 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 practice rate of vaginal birth after cesarean—VBAC. These attempts were highly successful, and VBAC rates rose from 3.4 percent in 1980 to a peak of 28.3 percent in 1996. This rate and a concomitant decline in total cesarean delivery rate or the United States, are shown in Figure 31-1. Also, a new lexicon was developed to describe these practices and outcomes (Table 31-1).
However, with the higher postcesarean vaginal delivery rate, reports of uterine rupture-related maternal and perinatal morbidity and mortality began to appear (McMahon, 1996; Sachs, 1999). These complications dampened prevailing enthusiasm for a trial of labor after cesarean section (TOLAC). They also prompted 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 when pursuing a TOLAC. Many believe that this one-word change—from readily to immediately available—was an impetus for the resulting decade-long decline in national VBAC rates illustrated in Figure 31-1 (Cheng, 2014; Leeman, 2013).
In a cross-sectional analysis between 1990 and 2009, the proportion of women with a prior cesarean delivery who underwent a TOLAC peaked in 1995, and slightly more than half of these women chose this option (Fig. 31-2). After this, the proportion of women attempting TOLAC declined to a nadir of16 percent in 2006 and subsequently rose to 21 percent through2009. Additionally, the percentage of VBACs reached its peak of 70 percent in 2000 but subsequently declined to a nadir of 38 percent in 2006 (Uddin, 2013).
FIGURE 31-1 Total, primary, and low-risk cesarean delivery (CD) rates and vaginal birth
after previous cesarean (VBAC) rates in the United States, 1989–2018. Epochs denoted
within rectangles represent contemporaneous ongoing events related to these rates.
ACOG = American College of Obstetricians and Gynecologists; NIH = National Institutes
of Health; PB = practice bulletin. (Data from Hamilton, 2015, 2016; Martin, 2019; National
Institutes of Health: NIH Consensus Development Conference, 2010.)
Using birth certificate data for 2013, Curtin and associates (2015) reported that only 1 in 5 women with one prior cesarean delivery attempted a TOLAC. In women with two or more prior cesarean deliveries, less than 1 in 10 women attempt a TOLAC, and half resulted in successful vaginal deliveries. At Parkland Hospital, although only 15 percent of women choose a TOLAC, the VBAC rate is 86 percent.
Thus, multiple interrelated factors— both medical and nonmedical— undoubtedly contributed to declining VBAC rates. Because of this, in 2010 the NIH convened a Consensus Development Conference Panel to study the issue. The panel report included a contemporaneous summary concerning the risks and benefits of repeat cesarean versus vaginal delivery. These findings were subsequently described and coupled with current recommendations by various professional organizations. As shown in Figure 31-1, it would seem that this report was followed by a slight rise in the VBAC rate.
INFLUENCING FACTORS
For the woman with a prior cesarean delivery, planning for future pregnancies and delivery route should begin with preconceptional counseling and be addressed again early in prenatal care. Importantly, decisions made throughout pregnancy regarding delivery mode are subject to continuing revisions as dictated by exigencies that arise during pregnancy. Assuming no mitigating circumstances, there are two basic choices. First a TOLAC offers the goal of achieving a VBAC. If cesarean delivery becomes necessary during the trial, it is a failed TOLAC. 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 delivery indication.
The decision regarding delivery mode should weigh clinical factors known to influence TOLAC success as well as benefits and risks (Table 31-2). As expected, TOLAC rates vary between institutions and providers. Last, economics, staffing, and medicolegal factors also may shape the decision to offer TOLAC.
DELIVERY ROUTE RISKS
As evidence mounted that the uterine rupture risk might be greater than expected, the American College of Obstetricians and Gynecologists (1988, 1994, 1998, 1999, 2015, 2019a,d) issued updated bulletins supporting TOLAC but also urging a more cautious approach. It is problematic that both options have risks and benefts to mother and etus but that these are not always congruent.
■ Maternal Risks
Rates of uterine rupture and associated complications clearly are increased with TOLAC. As shown in Table 31-1, uterine rupture typically is classified as either: (1) complete, when all uterine wall layers are separated, or (2) incomplete, when the uterine muscle is separated but the visceral peritoneum is intact. Incomplete rupture is also commonly reerred to as uterine dehiscence (Chap. 42, p. 742). It is these risks that underpin most of the angst in attempting TOLAC. Despite this, some argue that these factors should weigh only minimally in the decision because their absolute risk is low. For example, a systematic review by Guise and coworkers (2010) concludes that the uterine rupture risk was significantly elevated in women undergoing TOLAC—absolute risk of 0.47 percent and relative risk of 20.7—compared with women choosing ERCD.
The Maternal-Fetal Medicine Units (MFMU) Network conducted a prospective study at 19 medical centers (Landon, 2004). Shown in Table 31-3 are outcomes of nearly 18,000 women attempting TOLAC that were compared with those of more than 15,000 gravidas undergoing ERCD. Te absolute risk of uterine rupture was 0.7 percent compared with no reported uterine ruptures in the ERCD cohort. Various reports suggest either no or an increased mortality risk for ERCD compared with attempted OLAC (Guise, 2010; Wen, 2004).
Maternal morbidity estimates also are conicting. Te review by Guise and coworkers (2010) observed no signicant dierences in hysterectomy or transusion risk. But, another metaanalysis reported that women undergoing OLAC were approximately hal as likely to require transusion or hysterectomy compared with those undergoing ERCD (Mozurkewich, 2000). Conversely, in the MFMU Network study, the risks or transusion and inection were signicantly greater or women attempting OLAC (Landon, 2004). A recent large retrospective Canadian cohort study compared maternal and neonatal outcomes (Young, 2018). Te absolute rates o severe maternal morbidity and mortality were low. However, women attempting OLAC had signicantly higher adjusted risk ratios o uterine rupture (6.41), severe postpartum hemorrhage with transusion (2.80), and composite maternal morbidity (1.96) compared with women who underwent ERCD. Tis disparity is also ound among other studies. Importantly, compared with a successul OLAC, the risk o these major complications was veold greater with a ailed OLAC (Rossi, 2008).
■ perinatal Risks
In the Canadian study cited previously, rates o composite severe neonatal morbidity and mortality were higher among women delivering ater an attempted VBAC compared with those delivering by ERCD—adjusted odds ratio (aOR) 1.49 (Young, 2018). In this study ailed VBAC was also associated with a signicantly increased rate o neonatal death—aOR 3.22. Both the prospective MFMU Network study shown in able 31-3 and review by Guise (2010) ound signicantly higher perinatal mortality rates with OLAC compared with ERCD. In the latter review, the perinatal mortality rate with OLAC was 0.13 percent compared with 0.05 percent or ERCD. In the Canadian study cited previously, adjusted risk ratios or neonatal death (3.22) and or composite severe neonatal morbidity and mortality (1.49) were signicantly higher among women delivering ater an attempted OLAC compared with those delivering by ERCD (Young, 2018). In another study o nearly 25,000 women with a prior cesarean delivery, the OLAC-related perinatal death rate was 1.3 per 1000 among 15,515 women (Smith, 2002). Although this absolute risk is small, it is 11 times greater than the perinatal risk ound in 9014 women with ERCD.
OLAC also appears to be associated with a higher risk o hypoxic ischemic encephalopathy (HIE) compared with that or ERCD. Te MFMU Network study reported the incidence o encephalopathy at term to be 46 per 100,000 OLACs compared with zero cases in women undergoing ERCD (Landon, 2004). In the review by Guise (2010), the absolute risk o transient tachypnea o the newborn was slightly higher with ERCD compared with OLAC—4.2 versus 3.6 percent. But, neonatal bag and mask ventilation was used more oten in newborns delivered ollowing OLAC than in those delivered by ERCD—5.4 versus 2.5 percent. Te 5-minute Apgar scores or neonatal intensive care unit admission rates or newborns delivered by OLAC did not dier rom those delivered by ERCD.
TRIAL OF LABOR SELECTION
CONSIDERATIONS
Both patients and providers ideally would like individualized risks when counseling regarding the chance o successul OLAC. However, ew high-quality data guide selection o suitable OLAC candidates. Several OLAC/VBAC calculators can be used at entry to prenatal care and again at the time o labor to assist in successul OLAC prediction. However, these have not been validated as predictors o adverse maternal outcomes, such as uterine rupture. Similarly, algorithms and nomograms to aid prediction ail to demonstrated reasonable prognostic value (Grobman, 2007b, 2008, 2021; Metz, 2013; Wycko, 2020).
Lipschuetz and colleagues (2020) applied newer statistical analysis techniques to help improve prognostic accuracy. Despite the limitations o these predictive tools, several points are pertinent to candidate evaluation and are described subsequently. Current recommendations o the American College o Obstetricians and Gynecologists (2019d) are that most women with one prior low transverse hysterotomy are candidates, and i appropriate, they should be counseled regarding both OLAC and ERCD options. It is urther recommended that home birth is a contraindication or OLAC.
■ prior Uterine Incision
Prior Incision Type
Te type and number o prior cesarean deliveries are overriding actors in recommending OLAC (see able 31-2). And these caveats aim to avoid intrapartum uterine rupture. As shown in Table 31-4, women with one prior low transverse hysterotomy have the lowest risk o symptomatic scar separation. However, asymptomatic dehiscence or complete rupture is still a concern in these women (Fig. 31-3). Te uterine rupture risk in women with a prior vertical incision that did not extend into the undus is unclear. Martin (1997) and Shipp (1999) and their associates reported that these low vertical uterine incisions do not have a higher risk or rupture compared with low transverse incisions.
Te American College o Obstetricians and Gynecologists (2015) concluded that although evidence is limited, women with a prior vertical incision in the lower uterine segment without undal extension may be candidates or OLAC. Tis is in contrast to prior classical or -shaped uterine incisions, which are considered by most as contraindications to labor.
Te highest risks are with prior vertical incisions extending into the undus. Importantly, women with a classical uterine scar may rupture beore labor onset, and this may even occur beore term. Chauhun and colleagues (2002) reviewed 157 women with a prior classical cesarean incision. Tey used a policy o etal lung maturity assessment at 36 weeks and then delivery i mature. With a mean gestational age o 35.6 weeks at delivery, they reported one uterine rupture at 29 weeks that resulted in etal death; 9-percent uterine dehiscence rate; and 25-percent risk o maternal morbidity. For a woman with a prior classical cesarean delivery, the authors concluded that uterine rupture and dehiscence are neither predictable nor preventable despite early delivery. Te risk or earlier rupture is even greater in women who have undergone open maternal-etal surgery (Chmait, 2019; Goodnight, 2019).
Te American College o Obstetricians and Gynecologists (2021) recommends delivery between 360/7 and 370/7 weeks or a prior classical incision.
Although ew indications dictate a primary classical incision, 53 percent o women undergoing cesarean delivery between 240/7 weeks and 256/7 weeks have such an incision (Osmundson, 2013). By 28 weeks’ gestation, the risk drops to 35 percent and declines to <10 percent by 32 weeks. Te likelihood o classical uterine incision is also increased by noncephalic presentations. In those instances—or example, preterm breech etus with an undeveloped lower segment—the “low vertical” incision almost invariably extends into the active segment. From their review, Moramarco and colleagues (2020) reported that prior preterm classical cesarean delivery was associated with a 1-percent risk or rupture. Lannon and coworkers (2015) compared 456 women with a prior periviable cesarean delivery with more than 10,000 women whose prior cesarean delivery was done at term.
Te uterine rupture rate was 1.8 percent in the prior periviable group and 0.4 percent in the prior term group. O the uterine ruptures in the periviable group, hal were in women whose prior uterine incision was described as low transverse. Harper and associates (2009) did not conrm these ndings. Te type o uterine incision cannot be conrmed in all women. Unless clinical circumstances raise concern or a prior classical uterine incision, the American College o Obstetricians and Gynecologists (2019d) consider these women as potential OLAC candidates.
Special consideration is given to women with uterine mal- ormations who have undergone cesarean delivery. Earlier reports suggested that the uterine rupture risk in a subsequent pregnancy was greater than the risk in those with a normal uterus and a prior low transverse hysterotomy (Ravasia, 1999). However, in a study o 103 women with müllerian duct anomalies, there were no cases o uterine rupture (Erez, 2007).
Prior Incision Closure
As discussed in Chapter 30 (p. 558), the low transverse uterine incision can be sutured in either one or two layers. One metaanalysis compared single- versus double-layer closure and locking versus nonlocking suture or uterine closure (Roberge, 2014). Te uterine dehiscence or rupture rates or these closures did not dier signicantly. Both single-layer closure and closure that locked the rst layer, however, were associated with a reduced myometrial thickness during subsequent sonographic measurement. In contrast, Bennich and coworkers (2016) reported that a double-layer closure did not increase the residual myometrial thickness when saline contrast sonography was done several months postpartum. Our practice at Parkland
Hospital is to routinely suture the lower-segment incision with one running, locking suture line. Number of Prior Cesarean Incisions
At least three studies report a doubling or tripling o the uterine rupture rate in women with two compared with one prior transverse hysterotomy (Macones, 2005a; Miller, 1994; ahseen, 2010). In contrast, an analysis o the MFMU Network database did not conrm this (Landon, 2006). Namely, in 975 women with multiple prior cesarean deliveries, the rupture rate was 0.9 percent and not signicantly dierent rom the 0.7- percent rate in 16,915 women with a single prior operation.
Imaging of Prior Incision
Sonographic measurement o a prior hysterotomy incision has been used to predict rupture risk. Large deects in a nonpregnant uterus orecast a greater risk (Osser, 2011). Naji and coworkers (2013a,b) ound that the residual myometrial thickness decreased as pregnancy progressed and that rupture risk correlated positively with a thinner scar. Jastrow and colleagues (2010a) did a systematic review o women with a prior low transverse hysterotomy incision who underwent third-trimester sonographic evaluation. Tey concluded that a uterine scar deect was strongly predicted by a thin lower uterine segment. Tey dened this segment as the smallest measurement between urine in the maternal bladder and amnionic uid. Tat said, they could not nd an ideal threshold value to recommend sae OLAC. Tis same group subsequently recruited 1856 women contemplating vaginal birth ater a single low transverse incision, and they sonographically measured lower uterine segment thickness between 340/7 and 386/7 weeks (Jastrow, 2016). Women were grouped into three risk categories or uterine rupture during OLAC based on measurements: high risk <2.0 mm; intermediate risk 2.0 to 2.4 mm; and low risk ≥2.5 mm. Te OLAC rates were 9, 42, and 61 percent in the three categories, respectively. O the 984 OLACs, there were no symptomatic uterine ruptures. At Parkland Hospital, we do not assess the lower uterine segment in women with a prior cesarean delivery.
■ prior Uterine Ruture
Women who have previously sustained a uterine rupture are at greater risk or recurrence. As shown in able 31-4, those with a prior lower-segment rupture have up to a 6-percent recurrence risk, whereas prior upper-segment rupture coners a 9- to 32-percent risk (Reyes-Ceja, 1969; Ritchie, 1971). Sheth (1968) described outcomes o 21 subsequent pregnancies in 13 women who underwent uterine rupture repair. Rupture recurred in our pregnancies—approximately 20 percent. Usta and colleagues (2007) reported similar results. Fox and associates (2014) reported 14 women with prior uterine rupture and 30 women with prior uterine dehiscence. In 60 subsequent pregnancies, they noted no uterine ruptures or severe complications i women underwent ERCD prior to labor onset or immediately at the onset o preterm labor. Delivery is recommended between 360/7 and 370/7 weeks’ gestation (American College o Obstetricians and Gynecologists, 2021).
■ Interdelivery Interval
Magnetic resonance imaging studies o myometrial healing suggest that complete uterine involution and restoration o anatomy may require at least 6 months (Dicle, 1997). As a potential risk or uterine rupture, the relationship between interdelivery interval and uterine rupture in 2409 women with one prior cesarean delivery was examined (Shipp, 2001). Tere were 29 women with a uterine rupture—1.4 percent. Interdelivery intervals ≤18 months were associated with a threeold greater risk o symptomatic rupture during a subsequent OLAC compared with intervals >18 months. Similarly, Stamilio and associates (2007) noted a three- old augmented risk o uterine rupture in women with an interpregnancy interval <6 months compared with one ≥6 months.
■ prior Vaginal Delivery
Prior vaginal delivery, either beore or ater a cesarean birth, signicantly improves the prognosis or a successul OLAC (Grinstead, 2004; Hendler, 2004; Mercer, 2008). Prior vaginal delivery also lowers the OLAC-related risk o subsequent uterine rupture and other morbidities (Cahill, 2006; Hochler, 2014; Zelop, 1999).
■ prior Cesarean Delivery Indication
Women with a nonrecurring indication—or example, breech presentation—have the highest successul OLAC rate—nearly 90 percent (Wing, 1999). Tose with a prior cesarean delivery or etal compromise have an approximately 80-percent VBAC rate, and or those done or labor arrest, VBAC rates approximate only 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). A secondary analysis o the MFMU Cesarean Registry revealed that a prolonged second stage o labor— exceeding 3 hours—during OLAC will oten lead to VBAC. However, adverse maternal outcomes including uterine rupture or dehiscence were observed to be more common as the second stage lengthens (Hehir, 2018).
■ Fetal Size and Lie
Most studies show that increasing etal size is inversely related to VBAC rates. Te risk or uterine rupture is less robustly linked. Zelop and colleagues (2001) studied outcomes o almost 2750 women undergoing OLAC, and the uterine rupture rate increased—albeit not signicantly—with rising etal weight. Te rate was 1.0 percent or etal weight <4000 g, 1.6 percent or >4000 g, and 2.4 percent or >4250 g. Similarly, others have ound associated increased risks or uterine rupture with etuses >4000 g (Jastrow, 2010b). With preterm etuses, compared with term ones, women who attempt a OLAC have similar or higher VBAC rates and lower uterine rupture rates (Durnwald, 2006; Quiñones, 2005).
Few studies address the choice o OLAC or a singleton term breech etus. Very limited data suggest a possible link with adverse perinatal outcome (Azria, 2012; Macharey, 2017). Data supporting external cephalic version or breech presentation with a prior cesarean scar also are limited and are derived rom small studies (Impey, 2018; Weill, 2017). From these, version success and adverse event rates appear comparable with women without a prior cesarean delivery. Te American College o Obstetricians and Gynecologists (2020) does not consider a prior uterine incision to be a contraindication or attempted version. At Parkland Hospital, we do not attempt version or vaginal breech delivery in these women.
■ Multifetal Gestation
win pregnancy does not appear to increase the risk o uterine rupture. In one study o 1850 women with twins, the VBAC rate was 45 percent, and the rupture rate was 0.9 percent (Ford, 2006). Similar studies by Cahill (2005) and Varner (2007) and their coworkers reported rupture rates o 0.7 to 1.1 percent and VBAC rates o 75 to 85 percent. According to the American College o Obstetricians and Gynecologists (2019d), women with twins and a prior low transverse hysterotomy can saely undergo OLAC.
■ Maternal Obesity
Multiple studies have reported an inverse relationship between prepregnancy body mass index (BMI) and successul OLAC rates (Juhasz, 2005; Wu, 2019). Hibbard and associates (2006) reported the ollowing rates: 85 percent with a normal 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 ≥40.
■ Fetal Deat
Most women with a prior cesarean delivery and etal death in the current pregnancy would preer a vaginal delivery. Although etal concerns are obviated, available data suggest that maternal risks are increased. Nearly 46,000 women with a prior cesarean delivery in the MFMU Network database had a total o 209 etal deaths at an average gestational age o 32.8 weeks (Ramirez, 2010). O the 158 women who elected OLAC, the VBAC rate was 87 percent. In the entire OLAC group, the uterine rupture rate was 2.4 percent, and in 116 women who underwent an induction o labor, the rupture rate was 3.4 percent. Labor induction or second-trimester etal demise has a low complication rate (Bahar, 2021).
LABOR AND DELIVERY CONSIDERATIONS
■ Timing
Te American College o Obstetricians and Gynecologists (2019a) recommends delaying nonmedically indicated deliveries until 39 completed weeks o gestation or beyond. Data rom ita and colleagues in Figure 31-4 show signicant and appreciable adverse neonatal morbidity has been reported with ERCD beore 39 completed weeks (Chiossi, 2013; Clark, 2009). Tus, i ERCD is planned, it is essential that the etus be mature. Conversely, delaying delivery beyond 40 weeks is associated with higher neonatal morbidity rates. Accurate pregnancy dating is paramount prior to ERCD. Te American College o Obstetricians and Gynecologists (2019c) oers guidelines to assist in accurate pregnancy dating using a combination o last menstrual period and sonography. Te most accurate method to conrm or establish gestational age is by sonographic measurement o an early embryo-etus.
■ Intraartum Care
Because uterine rupture during OLAC may be unpredictable, the American College o Obstetricians and Gynecologists (2019d) recommends that labor in women attempting OLAC should be undertaken in acilities that can provide emergency cesarean delivery or situations associated with immediate threats to the lie o the women or her etus. I those resources are not available, the College recommends discussion o the hospital’s resources and availability o providers with the patient considering OLAC. Ultimately, the best alternative may be reerral to an institution with resources appropriate or OLAC.
Some argue that these provisions deny women ull access to choices. For example, in an earlier survey o Ohio hospitals, 15 percent o Level I, 63 percent o Level II, and 100 percent o Level III institutions met these requirements (Lavin, 2002). Moreover, an obstetrical anesthesia workorce survey reported that due to stafng limitations, OLAC was allowed in only 88 percent o hospitals with ≥1500 annual deliveries, in 59 percent o those with 500 to 1499 deliveries, and in 43 percent o those with <500 deliveries (raynor, 2016).
■ Cervical Riening and Labor Stimulation
Labor induction is associated with a higher OLAC ailure rate compared with spontaneous labor. Te risks or uterine rupture, however, are less clear with induction or augmentation, with the exception o prostaglandin E1 (PGE1)—misoprostol— which is contraindicated (American College o Obstetricians and Gynecologists, 2019d). O other considerations, induction or augmentation is ideally avoided in women with an unknown prior incision type, an unavorable cervix, or pregnancy >40 weeks. At Parkland Hospital we do not induce or augment labor pharmacologically in women electing OLAC. Instead, we attempt induction only by amniotomy.
Oxytocin
Use o oxytocin or labor induction or augmentation has been implicated in increased uterine rupture rates in women undergoing OLAC (Zelop, 1999). In the MFMU Network study reported by Landon (2004), uterine rupture was more requent in women induced with oxytocin alone—1.1 percent—compared with those presenting in spontaneous labor—0.4 percent. Labor augmentation was associated with uterine rupture in 0.9 percent. Among women in this cohort without a prior vaginal delivery, the uterine rupture risk associated with oxytocin induction was 1.8 percent—a ourold greater risk compared with spontaneous labor (Grobman, 2007a). In contrast, in one case-control study, induction was not associated with a higher rupture risk (Harper, 2012a). Cahill (2008) and Goetzl (2001) and their coworkers reported a dose-related risk o rupture with oxytocin.
Prostaglandins
Various prostaglandin preparations commonly employed or cervical ripening or labor induction are discussed in Chapter 26 (p. 489). Wing and colleagues (1998) compared misoprostol versus oxytocin or labor induction in women with a prior cesarean delivery. Tey terminated their trial ater two o the rst 17 women assigned to misoprostol developed a uterine rupture. Other studies conrmed this. Te American College o Obstetricians and Gynecologists (2019d) recommends that misoprostol should not be used or cervical ripening or labor induction in women at term with a prior cesarean delivery or major uterine surgery.
Studies using other prostaglandin agents or labor induction are contradictory. Ravasia and coworkers (2000) compared uterine rupture rates in 172 women given PGE2 gel with 1544 women in spontaneous labor. Te rupture rate o 2.9 percent was signicantly greater in women treated with PGE2 gel compared with 0.9 percent in those with spontaneous labor. Lydon-Rochelle and associates (2001) ound similar results. In the MFMU Network study cited previously, however, the uterine rupture rate was 1.4 percent when any prostaglandin was used in combination with oxytocin (Landon, 2004). But, in the subgroup o 227 women in whom labor was induced with a prostaglandin alone, there were no ruptures. Similar ndings were reported with intravaginal prostaglandins, which were not associated with a greater uterine rupture risk (Macones, 2005b). Tese latter investigators, along with Kayani and colleagues (2005), ound that sequential use o a prostaglandin ollowed by oxytocin was associated with a threeold greater rupture risk compared with spontaneous labor.
Mechanical Methods
In a retrospective study o 2479 women with a prior cesarean delivery, the uterine rupture risk using a transcervical Foley catheter or labor induction (1.6 percent) was not signicantly greater than that with spontaneous labor (1.1 percent)—or with amniotomy with or without oxytocin (1.2 percent) (Bujold, 2004). In 101 women induced with a balloon catheter, a 50-percent successul OLAC rate and no uterine ruptures was reported (Sarreau 2020). In contrast, Homan and coworkers (2004) described 138 women who underwent preinduction cervical ripening with a Foley catheter compared with 536 women who entered labor spontaneously. Te inordinately high intrapartum uterine rupture rate o 6.5 percent ollowing Foley catheter cervical ripening was greater than the 1.9-percent rate with spontaneous labor.
■ Eidural Analgesia
Concerns that epidural analgesia or labor might mask the pain o uterine rupture have not been veried. Fewer than 10 percent o women with scar separation experience pain and bleeding, and etal heart rate decelerations are the most likely sign o rupture (Kieser, 2002). Tat said, Cahill and associates (2010a) documented that more requent episodes o epidural catheter dosing were associated with increasing uterine rupture rates. VBAC rates are similar, and in some cases higher, among women with labor epidural analgesia compared with those using other analgesia orms (Landon, 2005). Perhaps related, almost a ourth o VBAC deliveries were completed with either orceps or vacuum (Inbar, 2017). Te American Academy o Pediatrics and the American College o Obstetricians and Gynecologists (2017) have concluded that epidural analgesia may saely be used during OLAC.
■ Uterine Scar Exloration
Following VBAC, some clinicians routinely document the integrity o a prior scar by placing a hand through the dilated cervix and along the inner surace o the lower uterine segment. But, routine uterine exploration is considered by others to be unnecessary. In a longitudinal study o 3469 women who had a VBAC, seven uterine dehiscences and one uterine rupture yielded an overall event rate o 0.23 percent (Silberstein, 1998).
Tese investigators concluded that transcervical evaluation need only be perormed or those with severe third-stage bleeding. Currently, the benets o routine scar evaluation in the asymptomatic woman are unclear, however, surgical correction o a dehiscence is necessary or associated signicant bleeding. At Parkland Hospital, we routinely examine the lower uterine segment ollowing a VBAC and document its integrity. A large tear, a breach into the peritoneal cavity, and presence o active bleeding avor a decision or laparotomy and repair.
UTERINE SCAR RUpTURE
■ Diagnosis
Progress o labor in women attempting OLAC is similar to normal labor, and no specic pattern presages uterine rupture (Graseck, 2012; Harper, 2012b). Beore hypovolemic shock develops, symptoms and physical ndings in women with uterine rupture may appear bizarre unless the possibility is kept in mind. For example, hemoperitoneum rom a ruptured uterus may result in diaphragmatic irritation with pain reerred to the chest. Tis may suggest a diagnosis o pulmonary or amnionic uid embolism instead o uterine rupture. As the example shown in Figure 31-5, the most common sign o uterine rupture is a nonreassuring etal heart rate pattern with variable decelerations that may evolve into late decelerations and bradycardia.
In one report o 36 cases during OLAC, etal signs o uterine rupture were evident in 24, maternal signs in eight, and a combination o maternal and etal in three (Holmgren, 2012). Few women experience cessation o contractions ollowing uterine rupture, and the use o intrauterine pressure catheters does not assist reliably in the diagnosis (Rodriguez, 1989).
Te clinical appearance o uterine rupture associated with a OLAC may mirror that o placental abruption but with little appreciable pain or tenderness. Also, because most women in labor are treated or discomort with either narcotics or epidural analgesia, pain and tenderness may not be readily apparent. Ultimately, the diagnosis o uterine rupture becomes evident because o etal distress and occasionally because o maternal hypovolemia rom concealed hemorrhage. I the etal presenting part has already entered the pelvis with labor, loss o station may be detected by pelvic examination. I the etus is partly or totally extruded rom the uterine rupture site, abdominal palpation or vaginal examination may be helpul to identiy the presenting part, which will have moved away rom the pelvic inlet. A rm contracted uterus may at times be elt alongside the etus. Emergent sonography in the labor unit may be helpul.
FIGURE 31-5 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.
■ Management
With rupture and expulsion o the etus into the peritoneal cavity, the chances or intact etal survival are poor. Fetal condition depends on the degree to which the placental implantation remains intact, although this can change within minutes. Te only chance o intact etal survival is aorded by immediate delivery—most oten by laparotomy—otherwise, hypoxia is inevitable. I rupture is ollowed by total placental separation, very ew neurologically intact etuses will be salvaged. Tus, even in the best o circumstances, some etal outcomes will be impaired. Te Utah experiences are instructive here (Holmgren, 2012). O the 35 laboring patients with uterine rupture, the decision-to-delivery time was <18 minutes in 17, and none o these inants had an adverse neurological outcome. O the 18 born >18 minutes rom decision time, the three inants with long-term neurological impairments were delivered at 31, 40, and 42 minutes. Tere were no deaths, but severe neonatal neurological morbidity developed in 8 percent o this group o 35 women with uterine rupture. Importantly, delivery within 30 minutes did not prevent every case o low cord pH or low 5-minute Apgar score. When uterine rupture was identied and delivery was accomplished is less than 30 minutes, there was no long-term neonatal morbidity. In the MFMU Network study cited earlier, seven o the 114 uterine ruptures associated with OLAC—6 percent—were complicated by development o neonatal encephalopathy (Spong, 2007). Neonatal mortality rate is likewise increased several old. In a study using the Swedish Birth Registry, the risk o neonatal death ollowing uterine rupture was 5 percent (Kaczmarczyk, 2007). Maternal deaths rom uterine rupture are uncommon. O 2.5 million women who gave birth in Canada between 1991 and 2001, there were 1898 cases o uterine rupture, and our o these—0.2 percent—resulted in maternal death (Wen, 2005). In other regions o the world, however, maternal mortality rates are much higher. From rural India, the maternal mortality rate associated with uterine rupture was 30 percent (Chatterjee, 2007).
Following complete rupture during OLAC, hysterectomy may be required. In selected cases, however, suture repair with uterine preservation may be perormed. Subsequent pregnancy ollowing such repair was described earlier (p. 576). Bladder injury may be comorbid, and interrogation o its integrity is prudent (Chap. 30, p. 563) (Phipps, 2005; Webb, 2000).
MULTIpLE REpEAT CESAREAN DELIVERIES
Te incidences o some common complications or women with a prior transverse cesarean delivery who undergo an ERCD were shown in able 31-3 (Landon, 2004). Rates o these complications and o other serious maternal morbidity rise with the number o prior cesarean deliveries (Marshall, 2011). First, the incidence o placenta accreta spectrum (PAS), which includes placenta accreta, increta, or percreta increases markedly with the number o previous hysterotomies. In an MFMU Network cohort o 30,132 women who had rom one to six repeat cesarean deliveries, a signicant association between an accruing number o cesarean deliveries and PAS in women with placenta previa was noted (Fig. 31-6) (Silver, 2006). Te PAS rate grew rom 11 percent or women with a placenta previa undergoing their second cesarean delivery to 67 percent or women undergoing their th (Fig. 43-12, p. 761). Indeed, almost hal o cesarean hysterectomies done at Parkland Hospital are in women with one or more prior cesarean deliveries (Hernandez, 2013).
Other maternal morbidity data come rom the same MFMU Network cohort and are shown in Figure 31-6 (Silver, 2006). In addition, rates o bowel or bladder injury, admission to an intensive care unit or need or ventilator therapy, maternal mortality, and length o surgery and hospitalization showed signicantly rising trends. Similar results have been reported by others (Nisenblat, 2006; Usta, 2005). More difcult to quantiy are risks or bowel obstruction and pelvic pain rom peritoneal adhesive disease, both o which increase ater each successive cesarean delivery (Andol, 2010; Mankuta, 2013).
From the United Kingdom Obstetric Surveillance System (UKOSS), adverse sequelae in women with ve or more cesarean deliveries were described (Cook, 2013). Tese women had signicantly higher rates o morbidity compared with those with one prior operation. Specically, the major hemorrhage rate increased 18-old; visceral damage, 17-old; critical care admissions, 15-old; and delivery <37 weeks, sixold. Much o this morbidity was in the 18 percent who had a placenta previa or PAS. Tis same study showed higher neonatal complication rates stemming mainly rom indicated premature delivery.
VAGINAL BIRTh AFTER CESAREAN—2021
Unortunately or women and their providers, no large randomized trials compare maternal or neonatal outcomes in those pursuing either OLAC or ERCD. Most studies have compared actual routes o delivery rather than the intended route o delivery. Tus, we agree with Scott (2011) regarding a common-sense approach. Te woman—and i she wishes, her partner—are encouraged to actively participate with the provider in an inormed-consent discussion. Patient decision aids oten assist shared decision making (Poprzenczny, 2020). Although the absolute rates o adverse maternal and neonatal outcomes are low, OLAC is associated with a higher rate o both maternal and neonatal morbidity and mortality compared with ERCD. Counseling should include documentation o the prior uterine incision and discussion o risks, benets, and probable outcomes associated with OLAC or ERCD. Tis includes consideration o risks involving uture pregnancies. Ideally, counseling begins preconceptionally and continues throughout pregnancy, with exible options extending up to delivery. For women who desire OLAC despite a actor that increases their specic risk, additions to the consent orm are recommended by the American College o Obstetricians and Gynecologists (2019d). Bonanno and colleagues (2011) have provided such an example. sakiridis and coworkers (2018) have compared national guidelines o societies in the United States, Canada, and the United Kingdom. A composite o these recommendations o proessional society guidelines is shown in Table 31-5 (Dy, 2019). Guidelines that tend to be more conservative are shown in Table 31-6
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