Trial of labor after cesarean birth: Intrapartum management

INTRODUCTION — Intrapartum management of patients undergoing a trial of labor after cesarean (TOLAC) is similar to that in patients with an unscarred uterus, with some unique considerations, such as choice of cervical ripening/induction agent, intensity of cardiotocography, and required resources. The additional considerations derive from the increased risk of uterine rupture in these patients.

This topic will discuss the intrapartum management of TOLAC. Choosing the route of delivery and method of cervical ripening after a previous cesarean birth are reviewed separately. (See "Choosing the route of delivery after cesarean birth" and "Cervical ripening and induction of labor after a prior cesarean birth".)

FACILITY RESOURCES — Facilities in which patients attempt TOLAC should have the resources necessary to perform an emergency cesarean birth within an appropriate period of time, given the increased risk of uterine rupture in this setting. These resources include the following [1]:

●Clinicians capable of monitoring labor and performing an emergency cesarean birth

●Clinicians capable of providing obstetric anesthesia for emergency cesarean birth

●Nursing personnel to assist with emergency cesarean birth

●Clinicians capable of providing neonatal resuscitation

●Equipment necessary for personnel to provide these services

In situations in which such resources are not readily available, the clinician and patient need to discuss implications of the limited resources at the selected delivery facility and available options. (See "Choosing the route of delivery after cesarean birth", section on 'Facility resources for offering TOLAC'.)

PATIENT PREPARATION

Documentation of informed consent — Upon admission, we obtain consent for both TOLAC and repeat cesarean birth. Consent for the latter is important if an intrapartum cesarean birth becomes necessary. Ideally, patients have been thoroughly counseled about the risks and benefits of TOLAC versus planned repeat cesarean birth during the course of prenatal care. (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 'Candidates for TOLAC'.)

As part of the informed consent process, the patient should be informed of the overall rate of successful TOLAC. Since an individual's likelihood of achieving a vaginal birth after cesarean (VBAC) varies based on demographic and obstetric characteristics, more precise estimates of the likelihood of success can be provided by using a calculator, such as the following calculator for use at the time of entry into prenatal care (calculator 1).

In the author's practice, the patient is counseled about the risk of uterine rupture and the risks of serious maternal and neonatal morbidity and mortality if rupture occurs. For patients with one prior low transverse cesarean birth, the risk of uterine rupture is approximately 0.5 to 0.9 percent [2-7]. The discussion is documented in the medical record.

If new factors have developed since the decision for TOLAC was made that either modify the likelihood of VBAC (eg, patient is in the active phase of labor) or should be considered in decision making (eg, last ultrasound shows macrosomia), then the potential effects of these factors are discussed with the patient, their desire to proceed with TOLAC is confirmed, and the discussion and decision are documented in the medical record. (See "Choosing the route of delivery after cesarean birth", section on 'Calculators for use at admission for birth' and "Choosing the route of delivery after cesarean birth", section on 'Macrosomia'.)

Admission laboratory tests — A baseline hemoglobin or hematocrit measurement and a blood type and antibody screen are commonly obtained. Patients undergoing TOLAC can be considered at moderate risk of receiving a postpartum blood transfusion (2 percent rate of transfusion at term in Maternal-Fetal Medicine Units Network studies [8]). Type and screen enables rapid cross-matching of blood products if needed in an emergency. By comparison, a crossmatch order requires a type and screen as well as compatibility testing and preparation and labelling of specific red blood cell units for transfusion.

Intravenous access — We place intravenous access at admission to the labor unit in case intravenous medications, cesarean birth, and/or blood products become necessary.

Anesthesia evaluation — Evaluation by the anesthesia team at admission is prudent in case cesarean birth becomes necessary, as well as for reviewing options for labor analgesia. (See "Neuraxial analgesia for labor and delivery (including instrumental delivery)" and "Anesthesia for cesarean delivery".)

Neuraxial anesthesia may be used to provide adequate pain relief during labor. It does not appear to reduce the chances of VBAC or mask the signs and symptoms of uterine rupture [9,10]. Whether it is associated with an increased risk of uterine rupture is unclear as available data are conflicting [9,11]. In the author's practice, patients undergoing TOLAC are encouraged to have a neuraxial anesthetic as it can provide adequate anesthesia in the event of an emergency cesarean birth for suspected uterine rupture and thus can facilitate more rapid delivery of a compromised fetus than induction of general anesthesia.

Cardiotocography — Most experts recommend continuous monitoring of uterine activity and fetal heart rate during TOLAC given an increased risk of uterine rupture. The most common sign of uterine rupture is a fetal heart rate abnormality, which is often a sudden and dramatic change. Abnormal uterine contraction and fetal heart rate patterns associated with uterine rupture are reviewed in more detail separately. (See "Uterine rupture: After previous cesarean birth", section on 'Clinical manifestations of uterine rupture'.)

External fetal heart rate monitoring is as reliable as internal monitoring in most cases, but internal fetal heart rate monitoring is preferable when the externally derived tracing is difficult to obtain or interpret because of poor technical quality. (See "Intrapartum fetal heart rate monitoring: Overview".)

External uterine contraction monitoring is usually adequate; intrauterine pressure monitoring offers no advantages for early diagnosis of uterine rupture [12,13]. As in any labor, intrauterine pressure catheters can and should be used when needed to evaluate the adequacy of the uterine contraction pattern. Use of intrauterine pressure catheters compared with external monitoring does not decrease the frequency of operative vaginal births or adverse neonatal outcomes [14]. (See "Use of intrauterine pressure catheters".)

LABOR MANAGEMENT — Many aspects of labor management are the same in patients with versus without a scarred uterus. (See "Labor and delivery: Management of the normal first stage".) The major differences are issues related to the use of pharmacotherapy for cervical ripening and stimulation of labor. (See 'Induction of labor' below.)

Assessment of labor progress — Labor progress is assessed by the same standards as in patients without a scarred uterus. (See "Labor: Overview of normal and abnormal progression".)

Although clinicians generally have a lower threshold for diagnosing failure to progress in patients undergoing TOLAC than they do in patients with an unscarred uterus, available evidence suggests that labor progress is similar in both groups [15-17]. For example:

●In a secondary analysis of Consortium on Safe Labor data, labor progress between 4 and 7 cm in patients undergoing TOLAC with no previous vaginal birth was slightly longer than that in nulliparous patients in spontaneous labor; however, this difference disappeared after adjustment for oxytocin dosing, suggesting that the slower progress may have been related to more conservative use of oxytocin in TOLAC patients [15]. The analysis was limited to patients with term, cephalic singletons with a normal neonatal outcome (ie, exclusion of neonates with neonatal intensive care unit admission, birth injury, or Apgar score <7 at five minutes).

●A retrospective cohort study of 5388 consecutive term births at a single institution reported similar durations for the first stage of labor (4 to 10 cm) among patients undergoing TOLAC and those with no history of cesarean birth (TOLAC patients: 3 hours, non-TOLAC patients: 2.8 hours) [16], suggesting that the same labor curve standards should be applied in the setting of TOLAC.

Prolonged latent phase — Patients with a prolonged latent phase can be offered therapeutic rest, oxytocin, and/or amniotomy to assist with transition to active phase, similar to the management of patients without a scarred uterus. (See "Labor: Diagnosis and management of the latent phase", section on 'Management issues'.)

Prolonged second stage — Decision-making regarding management of the second stage does not need to be modified in patients undergoing TOLAC. However, there should be a low threshold for operative birth if uterine rupture is suspected based on maternal vital signs or symptoms or the fetal heart rate tracing.

This conclusion is based, in part, on data from an observational study including over 4500 patients undergoing TOLAC who reached the second stage of labor [18]. The second stage was ≥3 hours in 7.8 percent. The likelihood of vaginal birth decreased with an increasing duration of the second stage: from 91 to 97 percent within the first 2 hours to 78 percent at 2 to <3 hours, 62 percent at 3 to <4 hours, and 46 percent at ≥4 hours. In addition, the frequency of uterine rupture or dehiscence significantly increased over time: from 0.7 percent at <1 hour to approximately 1.5 percent at 1 to <3 hours, to 3 percent at ≥3 hours. In contrast to other studies, the risk of adverse neonatal outcomes did not differ significantly by second-stage length.

Induction of labor — For patients planning TOLAC who require delivery before the onset of spontaneous labor, induction is a reasonable option in those with no standard contraindications to labor and vaginal birth.

Risks and outcome — Two concerns about inducing labor in patients with a prior cesarean birth are the potentially lower probability of vaginal birth after cesarean (VBAC) and increased risk for uterine rupture. The following data should be considered in shared decision making regarding induction versus planned repeat cesarean birth when prelabor delivery is indicated.

The benefits and harms of planned repeat cesarean birth versus induction of labor have not been evaluated by randomized trials [19]. In a meta-analysis of 14 cross-sectional studies including over 48,000 patients, the pooled rate of uterine rupture was lower in the spontaneous labor group than in the induced labor group (0.7 versus 2.2 percent) [20]. The pooled rate of VBAC was higher in the spontaneous labor group than in the induced labor group (74.3 versus 60.7 percent).

While there is no conclusive evidence that induction of patients with a prior cesarean birth increases the risk of uterine rupture, these and other epidemiologic studies suggest that this may be the case [2,21-26]. However, factors that attenuate the risk of rupture in these patients should also be considered. Those with a prior vaginal birth and/or a favorable cervix do not appear to be at increased risk of uterine rupture with induction [27,28]. Avoiding a prostaglandin for cervical ripening also appears to be important.

Techniques for cervical ripening — Options for induction of labor in patients with a TOLAC include mechanical ripening with a transcervical balloon catheter, amniotomy, and oxytocin. In the author's practice, cervical ripening, when indicated in the setting of TOLAC, is accomplished with a 60 mL transcervical balloon, transitioning to oxytocin and/or amniotomy when the cervix is favorable. Procedures for cervical ripening and induction in TOLAC, risk of rupture, and supporting evidence are discussed in detail separately. (See "Cervical ripening and induction of labor after a prior cesarean birth".)

Misoprostol (prostaglandin E1) appears to be associated with an increased risk of uterine rupture in patients with a prior cesarean birth, and expert opinion generally concurs that it should not be used in TOLAC (see "Cervical ripening and induction of labor after a prior cesarean birth", section on 'Use of prostaglandins'). Antepartum fetal demise is a special clinical situation that is discussed separately. (See "Stillbirth: Maternal care", section on 'Previous cesarean birth'.)

Labor pattern during induction — Compared with inductions in patients without a previous cesarean birth, induced labor in patients undergoing TOLAC appears to be associated with slower progression in the latent phase but equivalent labor progress in the active phase, but data are limited [15,24]. (See "Labor: Overview of normal and abnormal progression", section on 'Normal progression in induced labors'.)

Oxytocin augmentation — We manage patients whose labors do not follow generally accepted standards of labor progression in the active phase with oxytocin augmentation or repeat cesarean birth, as clinically appropriate (see "Labor: Overview of normal and abnormal progression"). The American College of Obstetricians and Gynecologists supports use of oxytocin for augmentation of labor in patients with a previous cesarean birth [1].

Data regarding the risk of uterine rupture from oxytocin augmentation of labor during TOLAC are conflicting. Three large observational studies reported an increased risk for uterine rupture with labor augmentation (OR 2.3 to 14, actual rate of rupture 0.9 to 1.9 percent) [2,29,30], and two others did not find an increased risk [3,31]. Small numbers of uterine ruptures and use of prostaglandin analogues for cervical ripening prior to augmentation of labor prevent definitive conclusions based on these findings.

It is unclear whether oxytocin regimens should be modified or an upper dose limit should be set to reduce the risk of rupture in patients undergoing TOLAC. Observational studies have suggested an association between oxytocin doses >20 milliunits/minute, tachysystole, and uterine rupture [19,21,32]. The low incidence of uterine rupture limits the power of these studies to detect small differences in dose-related risk of rupture.

Signs and symptoms of uterine rupture — Monitoring for evidence of uterine rupture is a critical component of intrapartum management of TOLAC. Signs and symptoms of uterine rupture may include fetal heart rate abnormalities (observed in 70 percent of cases), weakening contractions, loss of fetal station, abdominal pain, suprapubic pain at the level of the hysterotomy, need for frequent epidural dosing, vaginal bleeding, maternal hemodynamic instability, and hematuria. Clinical vigilance and careful evaluation are especially warranted in patients with persistent pain despite neuraxial anesthesia or need for frequent anesthetic redosing to achieve adequate pain control. (See "Uterine rupture: After previous cesarean birth".)

Amnioinfusion for management of variable decelerations — There are sparse data on amnioinfusion in patients undergoing TOLAC [33-36]. Although not a first-line approach, amnioinfusion can be used to relieve umbilical cord compression in patients undergoing TOLAC, similar to patients without a scarred uterus. An examination to ensure that there are no other signs or symptoms of uterine rupture should be performed before beginning the infusion since fetal heart rate decelerations may be sign of rupture. (See "Intrapartum category I, II, and III fetal heart rate tracings: Management", section on 'Variable decelerations without loss of variability or accelerations' and "Intrapartum category I, II, and III fetal heart rate tracings: Management", section on 'General approach'.)

We suggest monitoring the amount of fluid instilled and draining from the vagina to prevent over distention of the scarred uterine cavity (see "Amnioinfusion"). Uterine ruptures have been reported in these patients [34-36], but it is unknown whether the rates of rupture and cesarean birth are different from the rates in patients undergoing TOLAC with variable decelerations not treated with amnioinfusion.

DELIVERY — TOLAC involves the same techniques for fetal and placental extraction used for any other vaginal birth. (See "Labor and delivery: Management of the normal second stage".)

Operative vaginal birth — The indications, contraindications, prerequisites, and procedure for operative vaginal birth are the same as in patients without a scarred uterus. (See "Assisted (operative) vaginal birth".)

A secondary analysis of data from the Maternal-Fetal Medicine Units Network (MFMU) Cesarean Registry demonstrated that operative vaginal birth was associated with similar maternal and neonatal outcomes as cesarean birth for patients undergoing TOLAC with complete dilation and a fetus with descent to at least +2 station [37].

Management of a retained placenta — The third stage of labor should be managed as per usual practice for any vaginal birth. If the placenta is retained (ie, does not deliver with gentle cord traction for over 30 minutes), consideration should be given to the possibility of abnormal placentation (placenta accreta spectrum [PAS]) and appropriate preparations made. (See "Retained placenta after vaginal birth".)

Bedside ultrasound can be used to determine whether the placenta is merely trapped or still adherent, and if adherent, whether signs of PAS are present. A prudent approach in TOLAC patients is to evaluate the placenta sonographically prior to manual removal and to only attempt manual removal in the operating room so that hysterectomy can be performed rapidly if PAS is unexpectedly encountered. (See "Placenta accreta spectrum: Management".)

Uterine exploration — We do not routinely explore the uterus after a VBAC in a hemodynamically stable patient with no abnormal bleeding. No data support routine intrauterine examination to identify or treat asymptomatic scar dehiscence after a spontaneous vaginal birth.

It is likely that asymptomatic scar dehiscences occur frequently, and conservative management is reasonable. However, if the uterus is examined and dehiscence is detected, then it may be prudent to check serial hematocrit levels to further ensure that there is no laboratory evidence of occult intraperitoneal bleeding, which would be an indication for laparotomy and repair if confirmed.

On the other hand, if there is clinical suspicion that uterine rupture occurred during the second stage of labor, then manual uterine exploration should be performed. In postpartum patients, uterine rupture that occurred during delivery is characterized by pain and persistent vaginal bleeding despite use of uterotonic agents. Hematuria may occur if the rupture extends into the bladder.

Exploration of the lower uterine segment to evaluate for uterine rupture is also prudent after an operative vaginal birth performed for a terminal fetal bradycardia, even in the absence of excessive vaginal bleeding or abdominal pain, since terminal bradycardia can be a sign of rupture. This is not necessary if operative vaginal birth is performed for another indication. Clinical findings and management of uterine rupture are reviewed in more detail separately. (See "Uterine rupture: After previous cesarean birth", section on 'Clinical manifestations of uterine rupture' and "Uterine rupture: After previous cesarean birth", section on 'Management'.)

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".)

PATIENT PERSPECTIVE TOPIC — Patient perspectives are provided for selected disorders to help clinicians better understand the patient experience and patient concerns. These narratives may offer insights into patient values and preferences not included in other UpToDate topics. (See "Patient perspective: Trial of labor after cesarean birth".)

SUMMARY AND RECOMMENDATIONS

●Prerequisites – Facilities in which patients attempt a trial of labor after cesarean (TOLAC) should have the resources (personnel and equipment) necessary to perform emergency cesarean birth given the increased risk of uterine rupture in this setting. (See 'Facility resources' above.)

●Informed consent – Upon admission for anticipated TOLAC, women should be consented for both TOLAC and repeat cesarean birth. Informed consent for TOLAC should include a discussion of the risk of uterine rupture as well as the success rate of TOLAC. (See 'Documentation of informed consent' above.)

●Patient preparation

•Laboratory – A baseline hemoglobin or hematocrit and blood type and screen are obtained and an intravenous access is placed at admission in case cesarean birth, intravenous medications, and/or blood products become necessary. (See 'Admission laboratory tests' above and 'Intravenous access' above.)

•Cervical ripening – Transcervical catheters, oxytocin, and amniotomy are reasonable options for cervical ripening and labor induction in TOLAC. Misoprostol (prostaglandin E1) is associated with an increased risk of uterine rupture and should not be used; however, antepartum fetal demise is a special clinical situation and potential exception. (See 'Techniques for cervical ripening' above.)

●Anesthesia – Evaluation by the anesthesia team at admission is prudent in case cesarean birth becomes necessary, as well as for reviewing options for labor analgesia. Neuraxial anesthesia does not mask the symptoms of uterine rupture or decrease the likelihood of vaginal birth after cesarean. Neuraxial anesthesia also allows for rapid intervention in the setting of uterine rupture. (See 'Anesthesia evaluation' above.)

●Use of oxytocin – Both induction and augmentation are reasonable options for patients undergoing TOLAC. Clinical vigilance is warranted in these settings as some observational studies have reported an increased risk of uterine rupture with labor induction, and possibly with oxytocin augmentation. Patients with a prior vaginal birth and/or a favorable cervix do not appear to be at increased risk of uterine rupture with induction. (See 'Induction of labor' above and 'Oxytocin augmentation' above.)

●Monitoring during labor – We perform continuous monitoring of uterine activity and the fetal heart race tracing. Signs and symptoms of uterine rupture may include fetal heart rate abnormalities, weakening contractions, loss of fetal station, abdominal pain, suprapubic pain at the level of the hysterotomy, need for frequent epidural dosing, vaginal bleeding, maternal hemodynamic instability, and hematuria. Clinical vigilance and careful evaluation are especially warranted in patients with persistent pain despite neuraxial anesthesia or need for frequent redosing to achieve adequate pain control. (See 'Cardiotocography' above and 'Signs and symptoms of uterine rupture' above.)

●Labor progress – Available evidence suggests that labor progress is similar in patients undergoing TOLAC and those with an unscarred uterus. (See 'Assessment of labor progress' above.)

●Operative vaginal birth – The indications, contraindications, prerequisites, and procedure for operative vaginal birth are the same as in patients without a scarred uterus (see "Assisted (operative) vaginal birth"). Outcomes are similar to those with cesarean birth in the second stage of labor. (See 'Operative vaginal birth' above.)

●Post-delivery uterine exploration – Routine uterine exploration at the time of delivery to evaluate for uterine rupture is unnecessary. If there is clinical suspicion that uterine rupture occurred during the second stage of labor (pain and persistent vaginal bleeding despite use of uterotonic agents), then manual uterine exploration should be performed. (See 'Uterine exploration' above.)

ACKNOWLEDGMENTS — The UpToDate editorial staff acknowledges C Edward Wells, MD, and F Gary Cunningham, MD, who contributed to an earlier version of this topic review.