Cervical ripening and induction of labor after a prior cesarean birth

INTRODUCTION — 

Patients who are planning a trial of labor after a previous cesarean (TOLAC) sometimes develop a maternal or fetal indication for intervention before the onset of spontaneous labor. In this population, some have suggested that labor induction (even with cervical ripening) may reduce the chance of a successful vaginal birth after cesarean (VBAC) and may increase the risk for uterine rupture.

The optimal cervical ripening and labor induction methods (ie, those that lead to the highest chance of VBAC and the lowest chance of uterine rupture) in this population have not been established [1]. Available evidence is inconclusive because no randomized trials have compared the outcome of labor induction after a prior cesarean with the outcome of either planned repeat cesarean birth or expectant management. Data are limited to findings from observational studies, which have several limitations, including inconsistent definitions of uterine rupture and dehiscence, wide variation in induction protocols (eg, cervical ripening method, timing and dose of prostaglandins (if used), oxytocin administration), heterogeneity in patient populations, and inconsistency in primary outcome measures [2].

Induction of labor with or without cervical ripening in patients attempting TOLAC will be reviewed here. Other issues related to TOLAC and issues related to repeat cesarean birth are discussed separately:

●(See "Choosing the route of delivery after cesarean birth" and "Trial of labor after cesarean birth: Intrapartum management".)

●(See "Repeat cesarean birth".)

LIKELIHOOD OF VBAC

With induction versus expectant management — The effect of labor induction compared with expectant management on the chance of VBAC remains uncertain. In some observational studies in which induction was compared with expectant management, induction was associated with a higher chance of VBAC. For example, in a study of over 12,000 patients with singleton gestations ≥39 weeks and one prior low transverse cesarean birth, induction at 39+0 to 39+3 weeks in the absence of an acute obstetric/medical indication was associated with a 30 percent higher chance of VBAC than expectant management (73.8 versus 61.3 percent, odds ratio 1.31, 95% CI 1.03-1.67) [3]. Similar results were reported by a subsequent study including nearly 200,000 individuals with one prior cesarean birth (adjusted risk ratio 1.32, 95% CI 1.28-1.36) [4]. However, other observational studies have not shown decreased risks of VBAC with induction at some gestational ages [5,6]. The discordant results reflect differences in the studies themselves; for example, some used administrative data while others used data abstracted from medical records, some focused on induction without medical indication while others included anyone undergoing induction; some limited the gestational age to full term pregnancies while others included preterm pregnancies. None included potentially important variables, such as Bishop score at baseline, that could bias the results. Although the only randomized trial of elective induction at 40 weeks versus expectant management until 41 weeks was small (60 participants), it showed induction increased the chance of VBAC (RR 2.0, 95% CI 1.13-3.52) [7]. The size of the study precluded meaningful analysis of maternal or neonatal morbidities.

Favorable risk factors — A prior vaginal birth is the factor most associated with induction resulting in a vaginal birth after cesarean (VBAC). In a study including over 3200 individuals who underwent induction after a prior cesarean, overall VBAC rates for those with versus without a prior vaginal birth were 83 and 51 percent, respectively [8]. Cervical status was also a factor associated with the chance of VBAC:

●Favorable cervix (Bishop score ≥6): VBAC rates with versus without a prior vaginal birth were 91 and 69 percent, respectively.

●Unfavorable cervix: VBAC rates with versus without a prior vaginal birth were 77 and 45 percent, respectively.

The VBAC rate in induced labor appears to be similar whether one or two prior cesareans have been performed previously (69 versus 65 percent in one study [9]).

INDUCTION-RELATED RISK OF RUPTURE

Frequency of rupture — In patients with a prior cesarean, induction has been associated with a statistically higher rate of uterine rupture than spontaneous labor, although this relationship has not been as clear when induction was compared to expectant management. It should also be noted that, even in studies in which increases in risk of rupture for oxytocin induction versus spontaneous labor or expectant management were statistically significant, the absolute increases were relatively small (≤1 percent). For example:

●A large prospective Maternal-Fetal Medicine Units (MFMU) Network study reported the absolute risk of uterine rupture by labor status in patients with one or more cesarean births (17,898 TOLACs and 15,801 planned repeat cesarean births) [10]. In this study, patients who underwent induction with oxytocin alone had a threefold higher risk of uterine rupture compared with those in spontaneous labor (odds ratio [OR] 3.01, 95% CI 1.66-5.46), but the absolute differences in frequency of rupture were relatively small:

•Planned repeat cesarean birth without labor – 0 ruptures

•Spontaneous labor – 4 ruptures per 1000 spontaneously laboring patients

•Augmented labor – 9 ruptures per 1000 augmented labors

•Induced labor (oxytocin alone) – 11 ruptures per 1000 patients induced with oxytocin alone

•Induced labor (mechanical dilation with or without oxytocin) – 9 ruptures per 1000 patients induced with mechanical dilation with or without oxytocin

•Induced labor (any prostaglandin with or without oxytocin) – 14 ruptures per 1000 patients induced with prostaglandins with or without oxytocin

●In a secondary analysis of the MFMU study in which the patients were stratified by whether they had a prior vaginal birth, the risk of rupture with induction was only significantly higher than with spontaneous labor among those with no prior vaginal birth (no prior vaginal birth: 1.5 versus 0.8 percent; prior vaginal birth: 0.6 versus 0.4 percent) [8].

●In a meta-analysis of 14 cross-sectional studies including over 48,000 patients undergoing TOLAC, the pooled rate of uterine rupture was threefold higher in the induced labor group compared with the spontaneous labor group (2.2 versus 0.7 percent) [11]. The rate of oxytocin use in the induced and spontaneous labor groups was 61 and 40 percent, respectively. When the frequency of rupture was assessed with respect to oxytocin exposure, the pooled rate of uterine rupture in patients exposed to oxytocin was threefold higher than in the unexposed group (1.4 versus 0.5 percent).

●In a study comparing uterine rupture rates in patients induced in the 39^th, 40^th, and 41^st week of gestation (1603 patients) with those undergoing expectant management (11,072 patients), the frequency of uterine rupture was consistent and two- to threefold higher in the induction group (1.4 versus 0.5, 1.3 versus 0.6, and 1.3 versus 0.4 percent, respectively) [3].

As with likelihood of VBAC, the relationship between induction of labor and uterine rupture is less clear when the comparison group is expectant management, which is the clinically relevant comparator for decision-making. Three of the observational studies noted above evaluated uterine rupture, two showed no difference between those induced and those expectantly managed [4,5], and one showed an increased risk with induction (1.4 versus 0.5 percent) [3]. In the only randomized trial, which included only 60 patients, only one uterine dehiscence occurred and it was in the expectant management group [7].

Risk factors for rupture during induction — Factors that have been associated with an increased risk of rupture during induction after a previous cesarean (TOLAC) include:

●No previous vaginal birth [8,12] – In one study, the risk of rupture during induced TOLAC in patients with no previous vaginal birth versus a prior vaginal birth was 1.5 and 0.6 percent, respectively [8].

●Unfavorable cervix – In a nested case-control study including over 13,000 patients undergoing TOLAC, induction with an unfavorable cervix (defined as initial cervical dilation <2 cm) was associated with a fourfold increase in risk of rupture compared with spontaneous labor (hazard ratio [HR] 4.09, 95% CI 1.82-9.17), whereas induction with a favorable cervix (defined as initial cervical dilation >4 cm) was not associated with a statistically increased risk of rupture compared with spontaneous labor (HR 1.5, 95% CI 0.97-2.36) [12].

However, this association has not been reported consistently. In a study including over 6,000 patients with no prior vaginal birth undergoing TOLAC, an unfavorable cervix at labor induction was not associated with an increased risk of uterine rupture compared with a favorable cervix [8].

●Use of prostaglandins – Induction with prostaglandins appears to be associated with a higher risk for uterine rupture than induction with oxytocin or cervical ripening with mechanical methods followed by oxytocin administration. These data are described below. (See 'Use of prostaglandins' below.)

However, we do not know whether no previous vaginal birth and an unfavorable cervix increase the risk of rupture specifically in the setting of induction or whether these factors are generally associated with an increased risk of rupture regardless of how labor is initiated.  

MANAGEMENT OF INDUCTION

Our approach — Based on the data described below and our experience, we approach induction in patients who wish to undergo a trial of labor after a previous cesarean (TOLAC) as follows:

●For patients with maternal or fetal indications for induction, we discuss the risks and benefits of induction versus planned repeat cesarean birth, as well as the risks associated with waiting for spontaneous labor and the uncertainties in existing data, individualizing the discussion based on the specific clinical scenario and a person-centered approach. Clinical decision-making should take into account personal factors, including the presence or absence of antecedent uterine activity, cervical favorability, gestational age, past history of vaginal birth, and the indication for the induction. (See "Choosing the route of delivery after cesarean birth".)

The American College of Obstetricians and Gynecologists (ACOG) acknowledges that induction of labor is an acceptable option for individuals undergoing TOLAC [13]. They advise counseling patients as to the risks and benefits of oxytocin use in this setting. (See 'Risk factors for rupture during induction' above and "Choosing the route of delivery after cesarean birth", section on 'Predicting the probability of VBAC'.)

●For patients with a favorable cervix who choose to be induced, we perform amniotomy and administer oxytocin. There is no universally accepted definition of favorable or unfavorable cervix, although many clinicians consider a Bishop score ≥6 as the criterion for a favorable cervix (table 1). (See 'Issues related to use of oxytocin' below and "Induction of labor with oxytocin", section on 'Oxytocin administration' and 'Issues related to amniotomy' below.)

●For patients with an unfavorable cervix who choose to be induced, we use mechanical cervical ripening (insertion of a balloon catheter) followed by amniotomy and oxytocin administration. Many clinicians consider a Bishop score <6 indicative of an unfavorable cervix and the need for a ripening agent, while others use a lower threshold (eg, ≤3 or 4). Mechanical cervical ripening may shorten the duration of labor and avoid the possible increase in risk of uterine rupture associated with prostaglandin ripening agents, but does not eliminate the risk of rupture, which can occur even before the onset of labor. (See 'Issues related to use of mechanical methods of cervical ripening' below and 'Issues related to use of oxytocin' below and 'Issues related to amniotomy' below.)

Issues related to use of oxytocin

●Risk of rupture associated with oxytocin use – This risk is generally reported to be in the range of approximately 0.6 to 1.5 percent; the frequency varies among studies depending to some extent on patients' individual circumstances. (See 'Frequency of rupture' above.)

●Recommendations for oxytocin dosing – No high-quality data are available as to the optimal oxytocin protocol (eg, starting dose and rate of increase) that should be used; dosing options are shown in the table (table 2). For patients who have had a previous cesarean birth or other extensive transmyometrial surgery, some UpToDate contributors suggest using a low- rather than high-dose regimen, while others do not specifically avoid high-dose regimens in these patients. A typical low-dose regimen would involve a low starting dose (0.5 to 2 milliunits/min) and incremental increases of 1 to 2 milliunits/min at 15- to 40-minute intervals. Those who prefer this approach do so because of concern for uterine rupture, but acknowledge that data regarding any association between risk of rupture and oxytocin starting dose and incremental increases in dose are limited and no randomized trials have compared oxytocin dosing regimens in TOLAC. It cannot be assumed that slower incremental increases are safer because a longer labor might increase the risk of rupture. The maximum safe dose is also unclear. Although many labor units use 20 milliunits/min, this is somewhat arbitrary, absolute risk differences between this maximum and higher maximums appear to be relatively small (<1 percent in a study that looked at this [14]), and confounding by indication is possible (eg, dystocia may be the reason for higher doses). A prudent approach is to require the physician to be notified when 20 milliunits/min is reached and sign off on further increases depending on their assessment of contraction frequency, labor progress, and other patient-specific factors, balancing the risks and benefits on a case-by case basis.

Available data include the following:

•A case-control study of patients undergoing TOLAC found no association between the initial oxytocin dose, maximum dose, or time to maximum dose and uterine rupture in unadjusted analysis, but the rarity of rupture (24 cases among 1650 patients over 12 years) limited the ability to detect small differences [15].

•A retrospective cohort study of patients undergoing TOLAC reported the incidence of rupture at oxytocin doses of 1 to 5, 6 to 10, 11 to 20, and 21 to 30 milliunits/min was 1.13, 1.31, 1.78. and 2.07 percent, respectively [14]. A dose-response relationship between maximum oxytocin dose and uterine rupture was statistically significant beginning at 6 to 10 milliunits/minute (adjusted OR 1.97, 95% CI 1.15-3.37). This study included 5500 patients exposed to oxytocin, of whom 80 had a uterine rupture. There were 48 ruptures among the 8200 patients unexposed to oxytocin.

•A nested case-control study by the same group noted that maximum oxytocin doses above 20 milliunits/min increased the risk of uterine rupture fourfold in patients undergoing TOLAC (21 to 30 milliunits/min: HR 3.92, 95% CI 1.06-14.52; 31 to 40 milliunits/min: HR 4.57, 95% CI 1.00-20.82) [16]. The study included 272 patients exposed to oxytocin of whom 62 had a uterine rupture. The true risk of rupture at this maximum dose remains uncertain given the wide confidence intervals with a lower threshold including/approaching 1.0 and the risk of bias in observational data. (See "Induction of labor with oxytocin", section on 'Oxytocin administration'.)

Issues related to use of mechanical methods of cervical ripening

●Risk of rupture associated with use of balloon catheters – Data on mechanical methods of cervical ripening in this population are limited by small sample size, retrospective analyses, and institutional variation in protocols.

In a 2016 meta-analysis of 16 studies (mostly retrospective) including a total of 1447 patients, the risk of uterine rupture was more than twofold higher in patients with a previous cesarean who had a balloon catheter placed as part of cervical ripening or labor induction compared with those who experienced spontaneous onset of labor (OR 2.45, 95% CI 1.34-4.47, 18/1447 [1.2 percent] versus 45/6364 [0.7 percent]) [17]. However, nine of the ruptures occurred in a single study during active labor (not during cervical ripening), and when this study was excluded, the risk of uterine rupture was similar in the balloon catheter and the spontaneous labor groups. The increased risk of rupture reported in some studies may be related to the characteristics of patients who received balloon catheters rather than to the device itself. Specifically, patients who receive any ripening agent are different from those undergoing spontaneous labor (who are not eligible to receive a ripening agent) so comparing these two groups does not provide insight into the relevant clinical question as to whether the use of any ripening agent during induction results in a higher rate of rupture than expectant management, the relevant comparator.  

●Recommendation on use of balloon catheters – Given the limitations of the data described above, use of a balloon catheter is reasonable in a patient with a previous cesarean who is a candidate for induction but who has an unfavorable cervix. The choice of balloon catheter is based on clinician preference as comparative safety and efficacy data (single versus double balloon, 30 versus 80 mL of fluid) are limited [18]. The procedure for utilizing mechanical methods of cervical ripening is described separately and is not modified for patients with a previous cesarean birth. (See "Induction of labor: Techniques for preinduction cervical ripening", section on 'Mechanical methods'.)

The guidelines of the Society of Obstetricians and Gynaecologists of Canada (SOGC) state "a balloon catheter may be safely used to ripen the cervix in a patient planning a trial of labor (TOL) after cesarean birth" [19]. ACOG's position is "given the lack of compelling data suggesting increased risk with mechanical dilation and transcervical catheters, such interventions may be an option for TOLAC candidates with an unfavorable cervix" [13].

Outpatient cervical ripening in patients undergoing TOLAC is contraindicated in most protocols because of concern that an individual with a prior cesarean is at greater risk (regardless of ripening approach) for uterine rupture. Consequently, these patients have often been excluded from studies on outpatient cervical ripening, resulting in a lack of safety and outcome data.

Issues related to amniotomy — Amniotomy is performed if the head is well apposed to the cervix; if not, it is delayed until the head is well apposed to reduce the risk of cord prolapse. Although amniotomy has not been extensively studied in patients undergoing induction after a previous cesarean birth, in meta-analyses of randomized trials primarily in the general obstetric population, routine early amniotomy after cervical ripening reduced the interval from induction to delivery compared with usual care (mean reduction -4.95 hours, 95% CI -8.12 to -1.78 hours) [20], and the combination of oxytocin plus amniotomy reduced the chances of not achieving a vaginal birth within 24 hours compared with use of either oxytocin or amniotomy alone [21,22].

Controversial approaches

Use of prostaglandins

●Risk of rupture with use of prostaglandins – There are no data from large randomized trials and a paucity of data from good-quality observational studies regarding the effects of prostaglandins alone or in combination with other agents for cervical ripening in the setting of TOLAC. Much of the data on use of prostaglandins in patients with a prior cesarean birth were derived from observational studies in which misoprostol (prostaglandin E1) was used, and reports on use of other prostaglandins, such as prostaglandin E2, are limited by the small number of patients, the coadministration of other agents, and the lack of stratification by prior vaginal birth.

•Unspecified prostaglandin – Concern regarding the use of prostaglandins was stimulated by the 2001 publication of a population-based retrospective cohort study that analyzed data from 20,095 primiparous patients who gave birth after a single prior cesarean [23]. In this study, the rate of uterine rupture was similar for patients in spontaneous labor and those who were induced without the use of a prostaglandin, but was significantly higher in patients induced with prostaglandins (type not available). Specifically, the rate of uterine rupture by category was:

-Planned repeat cesarean birth without labor – 1.6 ruptures per 1000 planned repeat cesarean births.

-Spontaneous labor – 5.2 ruptures per 1000 spontaneous labors.

-Induced labor (no prostaglandins) – 7.7 ruptures per 1000 induced labors without use of prostaglandins.

-Induced labor (with prostaglandins) – 24.5 ruptures per 1000 induced labors with use of prostaglandins. Compared with planned repeat cesarean birth, the relative risk of rupture with use of prostaglandins was 15.6 (95% CI 8.1-30.0).

However, all of the information in this study was derived from a database using hospital discharge coding and birth certificates; individual chart reviews were not performed to verify the uterine ruptures or medications administered. Thus, there is a significant potential for missing and inaccurate data [24].

The high risk of uterine rupture reported in this retrospective study was not confirmed in the 2004 large prospective Maternal-Fetal Medicine Units Network study discussed above [10]. In that study, the uterine rupture rate among patients induced with a prostaglandin with or without oxytocin was much lower: 14 per 1000 induced labors. (See 'Frequency of rupture' above.)

The conflicting findings in these two studies may be due to heterogeneous approaches to prostaglandin use for cervical ripening (including the type of prostaglandin used) and to oxytocin administration. In addition, the increased risk of rupture may be related to characteristics of patients who receive prostaglandins rather than to the medication itself. In particular, patients who receive prostaglandins are much more likely to have an unfavorable cervix than those induced with oxytocin alone or who enter labor spontaneously. Although some studies describe outcomes for labors induced with oxytocin alone, few describe outcomes with use of prostaglandins alone. In one such study, prostaglandins alone were not associated with uterine rupture, but sequential use of prostaglandin and oxytocin was associated with uterine rupture (OR 3.07, 95% CI 0.98-9.88) [25].

•PGE2 – PGE2 may not be associated with an increased risk of uterine rupture. A 2021 meta-analysis of studies of uterine rupture among patients with one prior low-transverse cesarean birth undergoing labor induction with PGE2 estimated a pooled prevalence of five uterine ruptures per 1000 labor inductions (95% CI 2-9 per 1000), which is similar to historic rates reported for labor induction among patients with one prior low transverse cesarean [26]. Limitations included moderate heterogeneity among studies and lack of analysis of whether the prevalence differed substantially by specific characteristics, such as among those with versus without a prior vaginal birth.

•Misoprostol (PGE1) – A randomized trial on use of misoprostol for cervical ripening for labor induction in patients with previous cesarean births was stopped early because of safety concerns [27]. This trial and several case reports have led some investigators to conclude that misoprostol may be associated with a higher risk of uterine rupture than PGE2 and, therefore, should not be used in patients attempting TOLAC [27-31].

●Recommendations on use of prostaglandins — We do not use misoprostol (prostaglandin E1) or prostaglandin E2 for cervical ripening in patients with a previous cesarean birth, given that mechanical methods are readily available, effective, and may be safer.

•ACOG advises not using misoprostol for cervical ripening or labor induction in patients at term with prior uterine incisions [13] and does not address use of prostaglandin E2.

•SOGC came to similar conclusions regarding the use of misoprostol. They allowed the use of prostaglandin E2 (dinoprostone) but only in rare circumstances and after appropriate counseling [19].

•The National Institute for Health and Care Excellence in the United Kingdom concluded that, if delivery is indicated, patients who have had a previous cesarean may be offered induction of labor with vaginal prostaglandin E2 [32].

Role of intrauterine pressure catheter — Available evidence does not support use of an intrauterine pressure catheter (IUPC) as a means to identify uterine activity patterns that can be used to predict rupture. As an example, a study that calculated Montevideo units in patients undergoing TOLAC found no association between number of Montevideo units and risk of uterine rupture [33]. IUPCs can be used for standard clinical indications. (See "Use of intrauterine pressure catheters", section on 'Clinical uses'.)

CERVICAL RIPENING AND INDUCTION IN SPECIAL SITUATIONS

Fetal demise — The overall risks and benefits of induction in the setting of a prior cesarean birth are different when a fetal demise has occurred and thus the fetus is not at risk of harm from uterine rupture. Management of fetal demise in a patient with a prior cesarean birth is reviewed separately. (See "Stillbirth: Maternal care and prognosis".)

Pregnancies undelivered at 41 weeks of gestation — We suggest intervention for individuals who remain undelivered at 41 weeks of gestation (see "Postterm pregnancy"). Our approach in these cases is the same as that described above for labor induction (see 'Our approach' above). Patients with a favorable cervix are offered induction with amniotomy and oxytocin or repeat cesarean birth; patients with an unfavorable cervix are offered cervical ripening with a balloon catheter followed by amniotomy and oxytocin or repeat cesarean birth. As noted above, counseling should take into account a variety of factors, including chances of vaginal birth after cesarean and future reproductive plans.

DURATION AND PROGRESSION OF LABOR — 

In patients with a previous cesarean birth, the overall duration of labor appears to be approximately two hours longer for induction than for spontaneous labor [34], primarily related to a longer latent phase [35]. Therefore, when assessing labor progression in patients undergoing an induced trial of labor after a previous cesarean, it is reasonable for clinicians to apply the same criteria for making the diagnosis of a protraction or arrest disorder in the active phase or in the second stage as in patients without a previous cesarean birth undergoing induction. (See "Labor: Overview of normal and abnormal progression", section on 'Normal progression in induced labors' and "Labor: Overview of normal and abnormal progression", section on 'Overview of protraction and arrest disorders'.)

SOCIETY GUIDELINE LINKS — 

Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Cesarean birth".)

INFORMATION FOR PATIENTS — 

UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Vaginal birth after a cesarean (The Basics)")

SUMMARY AND RECOMMENDATIONS

●Success rate – In a general population, at least 60 percent of inductions in patients with one or two prior cesarean births results in a vaginal birth, with the highest chance of success in patients with a prior vaginal birth and favorable cervix. Whether induction alters the chance of vaginal birth after cesarean (VBAC) compared with expectant management is unclear. (See 'Likelihood of VBAC' above.)

●Risk of rupture – Induced labor appears to be associated with a higher rate of uterine rupture than spontaneous labor, but the absolute difference is low. Inductions in patients with a previous vaginal birth appear to be associated with a lower risk of rupture than in those with no prior vaginal birth. Whether induction alters the chance of uterine rupture compared with expectant management is unclear. (See 'Risk factors for rupture during induction' above.)

●Procedure – Based on the data described above and our own experience, we approach induction in patients who desire a trial of labor after previous cesarean (TOLAC) as follows (see 'Our approach' above):

•Counseling – For patients with maternal or fetal indications for induction, we discuss the risks and benefits of induction versus repeat cesarean birth as well as the risks associated with waiting for spontaneous labor in this setting. Such counseling takes into account individual characteristics (eg, chance of VBAC). (See "Choosing the route of delivery after cesarean birth", section on 'Risks/benefits of TOLAC versus PRCB' and "Choosing the route of delivery after cesarean birth", section on 'Predicting the probability of VBAC'.)

•Method

-For patients with a favorable cervix who choose to be induced, we suggest amniotomy and administration of oxytocin rather than oxytocin alone (Grade 2C). (See 'Issues related to use of oxytocin' above and 'Our approach' above.)

-For patients with an unfavorable cervix who choose to be induced, we use mechanical cervical ripening with a balloon catheter followed by oxytocin and amniotomy. (See 'Issues related to use of mechanical methods of cervical ripening' above and 'Issues related to use of oxytocin' above and 'Use of prostaglandins' above.)

-We recommend not using misoprostol in patients with prior cesarean births (Grade 1C). We and other providers in the United States do not use vaginal prostaglandin E2 in this patient population, but it is considered an option in some other countries. (See 'Use of prostaglandins' above.)

ACKNOWLEDGMENT — 

The editorial staff at UpToDate would like to acknowledge Deborah A Wing, MD, MBA, who contributed to an earlier version of this topic review.