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Abstract

The primary cause of uterine scars is a previous cesarean. In women with a previous cesarean, the risks of maternal complications are rare and similar after a trial of labor after cesarean (TOLAC) and after an elective repeat cesarean delivery (ERCD), but the risk of uterine rupture is higher with TOLAC (level of evidence [LE]2). Maternal morbidity in women with previous cesareans is higher when TOLAC fails than when it leads to successful vaginal delivery (LE2). Although maternal morbidity increases progressively with the number of ERCD, maternal morbidity of TOLAC decreases with the number of successful previous TOLAC (LE2). The risk-benefit ratio considering the risks of short- and long-term maternal complications is favorable to TOLAC in most cases (LE3).

Globally, neonatal complications are rare regardless of the mode of delivery for women with previous cesareans. The risks of fetal, perinatal, and neonatal mortality during TOLAC are low. Nonetheless, these risks are significantly higher than those associated with ERCD (LE2). The risks of mask ventilation, intubation for meconium-stained amniotic fluid, and neonatal sepsis all increase in TOLAC (LE2). The risk of transient respiratory distress increases in ERCD (LE2). To reduce this risk, and except in particular situations, ERCD must not be performed before 39 weeks (grade B).

TOLAC is possible for women with a previous cesarean before 37 weeks, with 2 previous cesareans, with a uterine malformation, a low vertical incision or an unknown incision, with a myomectomy, postpartum fever, an interval of less than 6 months between the last cesarean delivery and the conception of the following pregnancy, if the obstetric conditions are favorable (professional consensus). ERCD is recommended in women with a scar in the uterine body (grade B) and a history of 3 or more cesareans (professional consensus). Ultrasound assessment of the risk of uterine rupture in women with uterine scars has not been shown to have any clinical utility and is therefore not recommended during pregnancy to help decide the mode of delivery (professional consensus). Use of X-ray pelvimetry to decide about TOLAC is associated with an increase in the repeat cesarean rate without any reduction in the rate of uterine rupture (LE2). It is unnecessary for deciding mode of delivery and for managing labor during TOLAC (grade C).

TOLAC should be encouraged for women with a previous vaginal delivery either before or after the cesarean, a favorable Bishop score or spontaneous labor, and for preterm births (grade C). For women with a fetus with an estimated weight of more than 4500 g, especially in the absence of a previous vaginal delivery and those with supermorbid obesity (BMI > 50), ERCD must be planned from the outset (grade C). For all of the other clinical situations envisioned (maternal age > 35 years, diabetes, morbid obesity, prolonged pregnancy, breech presentation and twin pregnancy), TOLAC is possible but the available data do not allow specific guidelines about the choice of mode of delivery, in view of the low levels of proof (grade C).

The decision about planned mode of delivery must be shared by the patient and her physician and made by the 8th month, taking into account the individual risk factors for TOLAC failure and uterine rupture (professional consensus). TOLAC is the preferred choice for women who do not have several risk factors (professional consensus). The availability onsite of an obstetrician and anesthetist must be pointed out to the patient. If the woman continues to prefer a repeat cesarean after adequate information and time to think about it, her preference should be honored (professional consensus).

Labor should be induced in woman with a previous cesarean only for medical indications (professional consensus). Induction of labor increases the risk of uterine rupture, which can be estimated at 1% if oxytocin is used and 2% with vaginal prostaglandins (LE2). Mechanical methods of induction have not been studied sufficiently. Misoprostol appears to increase the risk of uterine rupture strongly (LE4). Based on the information now available, its use is not recommended (professional consensus). Routine use of internal tocodynamometry does not prevent uterine rupture (professional consensus). The increased risk of uterine rupture associated with oxytocin use is dose-dependent (LE3). In the active phase, it is recommended that the total duration of failure to progress should not exceed 3 h; at that point, a cesarean should be performed (professional consensus). Epidural analgesia must be encouraged. The simple existence of a uterine scar is not an indication for a routine manual uterine examination after VBAC (grade C).

Abbreviations: ERCD - elective repeat cesarean delivery, LE - level of evidence, TOLAC - trial of labor after cesarean, VBAC - vaginal birth after cesarean.

Keywords: Cesarean section, Vaginal birth after cesarean, Trial of labor after cesarean, Maternal and neonatal morbidity,Maternal and neonatal mortality, Uterine rupture.

1. Introduction and method [1], [2], and [3]

The sponsor (the French College of Gynecologists and Obstetricians (CNGOF)) appointed a steering committee (Appendix A) to define the exact questions to be put to the experts, to choose the experts, follow their work and draft the synthesis of recommendations resulting from their work. The experts analyzed the scientific literature on the subject to answer the questions raised. A literature review identified the relevant articles through mid-2012 by searching the MEDLINE database and the Cochrane Library. The search was restricted to articles published in English and French. Priority was given to articles reporting results of original research, although review articles and commentaries were also consulted. Guidelines published by organizations or institutions such as the American College of Obstetricians and Gynecologists (ACOG) [4], the Royal College of Obstetricians and Gynaecologists (RCOG) [5], the Society of Obstetricians and Gynaecologists of Canada (SOGC) [6], the National Institute for Health and Clinical Excellence (NICE) [7], the Agency for Healthcare Research and Quality (AHRQ) [8], and the Haute Autorité de Santé (HAS) [9] as well as previous guidelines published by the CNGOF [10] were reviewed, and additional studies were located by reviewing bibliographies of identified articles. For each question, each overview of validated scientific data was assigned a level of evidence based on the quality of its data, in accordance with the framework defined by the HAS (French Health Authority), summarized below.

1.1. Quality of evidence assessment

LE1: very powerful randomized comparative trials, meta-analysis of randomized comparative trials;

LE2: not very powerful randomized trial, well-run non-randomized comparative studies, cohort studies;

LE3: case–control studies;

LE4: non-randomized comparative studies with large biases, retrospective studies, cross-sectional studies, and case series.

A synthesis of recommendations was drafted by the organizing committee based on the replies given by the expert authors. Each recommendation for practice was allocated a Level defined by the HAS as follows:

1.2. Classification of recommendations

Grade A: Recommendations are based on good and consistent scientific evidence

Grade B: Recommendations are based on limited or inconsistent scientific evidence

Grade C: Recommendations are based primarily on consensus and expert opinion

Professional consensus: In the absence of any conclusive scientific evidence, some practices have nevertheless been recommended on the basis of agreement between the members of the working group (professional consensus).

All texts were reviewed by persons not involved in the work, i.e., practitioners in the various specialties (Appendix A) concerned and working in varying situations (public, private, university or non-university establishments). Once the reviewing had been completed, changes were made, if appropriate, considering assessment of the quality of the evidence.

The original long texts in French are cited [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], and [21], but their individual references are not included here in view of the enormous space they would occupy in this article intended to summarize the guidelines.

 

2. Uterine scars: epidemiologic aspects [11]

The primary cause of uterine scars is a previous cesarean section. In France, the cesarean rate was 20.8% in 2010 compared with 15.5% in 1995. Over the same period, the prevalence of uterine scars increased from 8% to 11% among all parturients and from 14% to 19% among multiparas. The mode of delivery of women with previous cesareans varies quite substantially from one country to another. According to the 2010 national perinatal survey in France, 51% of such women had a cesarean before labor; among those who began labor, 75% delivered vaginally; overall, 36.5% had vaginal deliveries.

In developed countries, uterine scars are the principal risk factor for uterine rupture. Its overall incidence among women with previous cesareans is estimated between 0.1% and 0.5%. Uterine scars are also a major risk factor for abnormal placental insertion (placenta previa and accreta), and the risk increases with the number of scars.

 

3. The benefits and risks of trial of labor compared to elective repeat cesarean for women with a previous cesarean [12]

Maternal mortality remains a very rare event regardless of the mode of delivery in women with a previous cesarean (LE2). It may be slightly less rare in women who have a trial of labor after cesarean (TOLAC) (LE3). The risk of complete uterine rupture in TOLAC is significantly higher than in elective repeat cesarean delivery (ERCD) (LE2), but is nonetheless very low—approximately 0.2–0.8% in women with a single uterine scar (one previous cesarean). The occurrence of a surgical wound, principally of the bladder, also remains a rare event (less than 1%) after both TOLAC and ERCD (LE2).

Reports in the literature about the risks of hemorrhagic complications requiring a hysterectomy or blood transfusion are inconsistent; these differences are due to the heterogeneity of study populations. These risks nonetheless do not appear to differ very much according to planned mode of delivery (TOLAC or ERCD) (LE3). The risks of postpartum infections and of venous thrombosis or embolisms appear identical for TOLAC and ERCD and remain rare (LE3). The risk of infection is associated above all with maternal obesity (LE2). Hospitalization is longer after ERCD than after TOLAC (LE3).

Maternal morbidity in women with previous cesareans is higher when TOLAC fails than when it leads to successful vaginal delivery (LE2). The performance of an emergency cesarean increases the risks of surgical wounds, of hemorrhagic complications requiring hysterectomy or blood transfusion, and of infectious complications (postpartum endometritis) (LE2). Maternal morbidity after TOLAC decreases with the number of preceding successful vaginal births (LE2).

 

4. The neonatal benefits and risks of trial of labor compared to elective repeat cesarean in women with a previous cesarean [13]

Globally, neonatal complications are rare regardless of the mode of delivery for women with previous cesareans.

In utero fetal mortality is low but is higher in TOLAC (0.5/1000–2.3/1000) than in ERCD (0/1000–1.1/1000) (LE2). The absolute risk of perinatal mortality in TOLAC is small (1/1000–2.9/1000) but nonetheless significantly higher than in ERCD (0/1000–1.8/1000) (LE2). Similarly, the absolute risk of neonatal mortality is low in TOLAC (1.1/1000), but still significantly higher than in ERCD (0.6/1000) (LE2).

The prevalence of anoxic-ischemic encephalopathy is also slight but nonetheless significantly higher in TOLAC (0.8/1000) than in ERCD (0/1000) (LE3). The intubation rate for meconium-stained amniotic fluid is significantly higher in TOLAC than in ERCD (LE2), as are the rates of suspected and proven neonatal sepsis (5% and 1%, respectively, vs. 2% and 0%) (LE2). On the other hand, the risk of transient respiratory distress is significantly higher in ERCD (6%) than in TOLAC (3%) (LP2). To reduce this risk, and except in particular situations, ERCD must not be performed before 39 weeks (grade B).

Results of studies on the impact of mode of delivery on low Apgar scores are discordant and do not justify any conclusion (professional consensus). Most studies do not find that admission to the intensive care unit differs according to mode of delivery (TOLAC vs. ERCD) (LE3).

 

5. Factors influencing the mode of delivery in TOLAC [14]

Three factors are strongly associated with the success of TOLAC: a history of vaginal birth, especially if the vaginal delivery took place after the cesarean (LP2), a favorable Bishop score or a cervix considered favorable at entry into the labor room (LP2), and spontaneous labor (LE2).

Several factors are associated with a reduced TOLAC success rate: previous cesarean for failure to progress or non-descent at full dilatation (LE3), a history of two cesareans (although the TOLAC success rate remains high (70%)) (LE3), maternal age > 40 years (LE3), body mass index > 30 (LE3), pregnancy prolonged past 41 weeks (LE3), and birth weight > 4000 g (LE3). Nonetheless, ultrasound estimates of fetal weight are very imprecise, and the false-positive rate for predicting a birth weight greater than 4000 g is approximately 50% (LE2). Moreover, induction of labor, regardless of the method used, is associated with a lower success rate for TOLAC (LE2).

Use of X-ray pelvimetry to decide about TOLAC is associated with an increase in the repeat cesarean rate without any reduction in the rate of uterine rupture (LE2). It is unnecessary for deciding mode of delivery and for managing labor during TOLAC (grade C).

Scores and nomograms have only limited clinical utility in identifying the group of women at risk of cesarean delivery during labor (professional consensus).

 

6. Criteria for TOLAC according to characteristics of the uterine scar [15]

According to the current data, TOLAC can be attempted for women with uterine malformations if the incision for the preceding cesarean left a low transverse scar (professional consensus). No study of sufficient methodological quality justifies affirming the superiority of any particular type of uterine suture during a cesarean to reduce the risk of uterine rupture (professional consensus).

The level of evidence of the studies conducted to estimate the risk of rupture during pregnancy or during labor after a myomectomy is low (LE4). The risk of uterine rupture depends on the type of procedure performed (number of uterine incisions and of fibroids removed) (professional consensus). A laparoscopic or laparotomic myomectomy, if performed with minimal use of coagulation and uterine closure at more than one layer, is probably associated with a low risk of uterine rupture, so that vaginal delivery of a subsequent pregnancy remains possible (professional consensus). Hysteroscopic septum resection or perforation by monopolar coagulation could increase the risk of uterine rupture compared with an unscarred uterus, but the data are insufficient to recommend a planned cesarean (professional consensus).

A history of cesarean with a low vertical incision does not contraindicate TOLAC (professional consensus). A repeat cesarean is recommended if the incision is higher, into the uterine body, because of the higher risk of uterine rupture (grade B). An excess risk of uterine rupture in women with a history of postpartum fever has not been demonstrated. It is therefore not an indication for a repeat cesarean (professional consensus). The unavailability of a surgical report from the preceding cesarean is not a contraindication to TOLAC (professional consensus).

The risk of uterine rupture during TOLAC may be higher after two previous cesareans than after one (Le3). Nonetheless, TOLAC is possible in those cases when the obstetric situation is favorable (professional consensus). ERCD is recommended after 3 previous cesareans, except in situations of intrauterine fetal death or terminations of pregnancy (professional consensus).

The risk of uterine rupture increases as the interval between the previous cesarean delivery and the conception date of the following pregnancy decreases (LE3). TOLAC may nonetheless be allowed even when this interval is less than 6 months if the obstetric conditions are favorable (professional consensus).

A single previous cesarean before 37 weeks does not contraindicate TOLAC (professional consensus).

Ultrasound assessment of the risk of uterine rupture in women with uterine scars has not been shown to have any clinical utility and is therefore not recommended during pregnancy to decide mode of delivery (professional consensus).

In conclusion, TOLAC is possible in all of the situations studied except two: a uterine body incision during a previous cesarean and a history of at least 3 previous cesareans (professional consensus).

 

7. Particular maternal or fetal clinical situations that influence the choice of mode of delivery for women with a previous cesarean [16]

The failure rate for TOLAC increases with maternal age (LE3). The literature does not provide enough information to determine a maternal age threshold above which ERCD is preferable to TOLAC; nonetheless, the woman's obstetric future is an element to consider in determining her mode of delivery (professional consensus).

Grand multiparity is associated with a significant reduction in TOLAC failure and in the risk of uterine rupture (LE3). Accordingly, TOLAC should be encouraged for grand multiparas (grade C).

Independently of fetal macrosomia, diabetes before pregnancy reduces the likelihood of successful TOLAC (LE3). Pregnancy-related diabetes successfully managed by diet is not a risk factor for TOLAC failure (LE3). Diabetes, gestational or pre-existing, is not in itself a risk factor for uterine rupture (LE3). In the absence of fetal macrosomia, TOLAC is possible for patients with diabetes, regardless of its type or duration (grade C). Maternal morbid obesity (BMI > 40) is associated with a reduced success rate for TOLAC, but not with a significant increase in the risk of uterine rupture (LE3). TOLAC is thus possible for these patients (LE3). ERCD is preferable to TOLAC for women with a BMI > 50 because of their very high failure rate with TOLAC (87%) (grade C) and the difficulties in moving them rapidly in emergency situations (professional consensus).

The existence of a uterine scar does not appear to affect the success rate of external cephalic version (ECV) for breech presentation (LE3). No increased risk of uterine rupture is reported (LE4). ECV should be offered to women eligible for TOLAC (grade C). After a comparison of pelvimetry and fetal biometry shows the feasibility and in the absence of persistent deflexion (hyperextension) of the fetal head, TOLAC is possible for women with a fetus in breech presentation (professional consensus).

The success rate of TOLAC in twin pregnancies appears similar to that reported for singletons (LE3), and there is no clinically significant increase in the uterine rupture rate (LE3). TOLAC is thus possible for women carrying twins (grade C).

Macrosomia, defined post hoc by a birth weight > 4000 g, is associated with an increased risk of TOLAC failure (LE3) and a doubling of the uterine rupture rate (LE3). Nonetheless, the success rate of TOLAC remains sufficiently high (>60%) and the increase in the uterine rupture rate sufficiently minimal that suspected fetal macrosomia alone does not justify ERCD (grade C). Nonetheless, in cases of suspected fetal macrosomia where the estimated fetal weight is >4500 g, particularly in patients who have never had a vaginal delivery, the likelihood of successful TOLAC is low enough (<40%) (LE3) and the increase in the uterine rupture rate high enough (×3) (LE3) that ERCD is recommended (grade C).

The success rate of TOLAC before 37 weeks is similar to that of TOLAC at term, and the risk of uterine rupture is lower (LE3). Neonatal outcome is similar after TOLAC and ERCD before 37 weeks (LP3). Accordingly, TOLAC should be encouraged for women in preterm labor (grade C). Prolonged pregnancy is associated with a reduced TOLAC success rate but not with an increased risk of uterine rupture (LE3). TOLAC is possible for post-term women (after 41 weeks) (grade C).

No study has specifically dealt with the effect of intrauterine growth restriction on the risks of uterine rupture and TOLAC failure.

 

8. Guidelines for organization, planning and counseling TOLAC [17]

Because of the risks of TOLAC failure and of uterine rupture, a woman choosing TOLAC must not give birth either at home or in a birthing center (professional consensus). The risk of hemorrhagic complications accompanying uterine rupture or TOLAC failure also requires that the obstetrician be skilled in the surgical techniques for emergency hemostasis (professional consensus). In women with an anterior placenta covering the uterine scar, the risk of abnormal placental insertion, such as accreta, calls for delivery in a hospital that has available not only skilled obstetric surgeons but also rapid access to blood products and a continuous or intensive care unit for the mother (professional consensus).

TOLAC can take place at a maternity unit that does not have an obstetrician or an anesthetist onsite 24/7 (professional consensus). This situation exposes the woman to a higher risk that a cesarean cannot be performed rapidly (LE4). It is recommended that an obstetrician be present onsite when the obstetric context suggests a higher than normal risk of TOLAC failure or uterine rupture, e.g., induction of labor or abnormalities in either FHR or progression of labor (professional consensus).

It is recommended that an obstetrician validate the planned mode of delivery during the 8th month (professional consensus). The option chosen should be noted in the medical file, with its reasons, the date, and the obstetrician's name (professional consensus). A plan in the event that labor begins before an ERCD should also be stated clearly in the case record (professional consensus). Women with uterine scars should be counseled about both TOLAC and ERCD for their impending delivery (professional consensus). The information must mention whether an obstetrician and anesthetist are always present onsite (professional consensus). Depending on the obstetric context, additional information should be provided, especially if labor is induced (professional consensus).

It is also recommended that the obstetrician on call be routinely advised of the onset of labor and the obstetric situation and be asked to validate the TOLAC decision (professional consensus). It is recommended that the labor be monitored by the same person (except in cases of unavailability or shift changes) (professional consensus). All members of the staff—midwife, obstetrician and anesthetist—must pay careful attention to potential signs of rupture the (professional consensus). The obstetrician must be called immediately if there is any suspicion of uterine rupture (professional consensus).

It is recommended that after every cesarean delivery women be informed about the particularities of delivery with uterine scars, beginning during the postpartum period and especially during the postnatal visit (professional consensus). The information must specify that it is recommended to wait a year before a new conception (professional consensus). Information should again be dispensed during the pre-conceptional consultation, at the beginning of the pregnancy, and in the 8th month, in order to reach a shared decision at term (professional consensus). If the woman continues to prefer a repeat cesarean after adequate information and time to think about it, her preference should be honored (professional consensus).

 

9. Mode of induction of labor and management of labor in women with uterine scars [18]

9.1. Induction

Induction moderately increases the risk of cesarean delivery during labor, but approximately doubles the risk of uterine rupture compared with spontaneous labor in women with uterine scars (LE2). Labor should be induced in such women only for medical indications (professional consensus). Elective induction of labor for reasons of convenience must be avoided in women with prior cesareans (professional consensus). In cases of induction, a previous vaginal delivery and a favorable cervical examination are important factors to include in decision-making because they increase the likelihood of vaginal delivery (LE2). Labor should not be induced for women with two previous cesareans (professional consensus).

Induction of labor with oxytocin is associated with a minimal to moderate increase in the risk of uterine rupture compared with spontaneous labor (LE2). In terms of the risk/benefit ratio, prudent use of oxytocin for induction of labor is possible (grade C).

E2 prostaglandins, however, are associated with a significant increase in the risk of uterine rupture (LE2). The success rate of TOLAC falls in situations where prostaglandins are used (unfavorable cervical conditions). The decision to use them as a method of induction must take into account the obstetric and maternal factors that might influence the success of TOLAC. They must be used only with great prudence (professional consensus).

Misoprostol appears to substantially increase the risk of uterine rupture in women with uterine scars in the protocols that have thus far been studied (LE4). Based on the information now available, its use is not recommended (professional consensus).

The current data are insufficient to assess the risk of uterine rupture after induction of labor by a transcervical balloon. The most robust study reports a moderate increase in this risk (LE4). The prudent use of a transcervical balloon is possible for induction of labor in women with a previous cesarean (professional consensus).

In the case of terminations of pregnancy or intrauterine deaths for women with uterine scars, induction of labor appears preferable to a planned cesarean in most cases, regardless of the number of past cesareans (professional consensus). The most substantial data concern misoprostol but the levels of evidence are low (LE4). Fewer data are available about sulprostone and vaginal PGE2 than for misoprostol in this indication, although sulprostone is authorized in France for it. It nonetheless appears possible to use both, as a function of term or cervical condition (professional consensus). Preparation by mifepristone or the use of hygroscopic dilators is not contraindicated for women with previous cesareans (professional consensus). Women with more than one previous cesarean should be referred to a hospital with experience in the management of termination of pregnancy and with the appropriate technical equipment and facilities (professional consensus).

9.2. Management of labor

No evidence demonstrates the utility of routine internal tocodynamometry for surveillance of uterine tonus and activity during labor in women with a previous cesarean (professional consensus). Internal tocodynamometry can be a useful tool for recording contractions if the recording quality of external tocodynamometry is inadequate, but it can neither predict nor diagnose uterine rupture (professional consensus).

In TOLAC, continuous recording of the fetal heart rate is recommended from the onset of labor (professional consensus). The increased risk of uterine rupture associated with oxytocin use is dose-dependent (LE3). Oxytocin must not be routinely used in the management of TOLAC of women with previous cesareans (professional consensus). Should dilatation cease, an amniotomy is recommended as a first-line treatment (professional consensus). The lowest possible dose of oxytocin necessary to obtain satisfactory uterine dynamics is essential (professional consensus). In the active phase, it is recommended that the total duration of failure to progress should not exceed 3 h; at that point, a cesarean should be performed (professional consensus). There are no data to justify a recommendation during the latency period. The simple existence of a uterine scar is not an indication for a routine manual uterine examination after VBAC (grade C).

 

10. Uterine rupture: prediction, diagnosis, and management [19] and [20]

Uterine rupture occurs in 0.1–0.5% of women with uterine scars and 0.2–0.8% of women in TOLAC (LE2). It is associated with severe maternal morbidity in the order of 15% (hysterectomy, intensive care unit transfer, visceral injuries, and blood transfusions) (LE2). The morbidity observed during uterine rupture after a cesarean delivery nonetheless appears to be less severe than that observed during the rupture of an unscarred uterus (LE3). The maternal mortality associated with uterine rupture appears low (<1%) (LE3). The perinatal mortality associated with uterine rupture ranges from 3 to 6% at term (LE2) and the rate of asphyxia (umbilical artery pH <7.00 or neonatal encephalopathy) between 6 and 15% (LE2).

Two obstetric factors specifically influence the risk of uterine rupture: previous vaginal delivery (which reduces the risk) and induction of labor (which increases the risk) (LE3). In practice, the risk of uterine rupture is multifactorial and the published scores do not predict the risk of uterine rupture sufficiently well to be clinically useful (grade B).

The decision about mode of delivery must take into account the potential association of several factors related to the risk of uterine rupture as well as the factors that influence the TOLAC success rate (Table 1) (professional consensus).

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