Trial of labor in patients with a previous lower uterine vertical cesarean section

Trial of labor after cesarean, vaginal birth after cesarean, and the risk of uterine rupture: an expert review

The decision to pursue a trial of labor after cesarean delivery is complex and depends on patient preference, the likelihood of successful vaginal birth after cesarean delivery, assessment of the risks vs benefits of trial of labor after cesarean delivery, and available resources to support safe trial of labor after cesarean delivery at the planned birthing center. The most feared complication of trial of labor after cesarean delivery is uterine rupture, which can have catastrophic consequences, including substantial maternal and perinatal morbidity and mortality. Although the absolute risk of uterine rupture is low, several clinical, historical, obstetrical, and intrapartum factors have been associated with increased risk. It is therefore critical for clinicians managing patients during trial of labor after cesarean delivery to be aware of these risk factors to appropriately select candidates for trial of labor after cesarean delivery and maximize the safety and benefits while minimizing the risks. Caution is advised when considering labor augmentation and induction in patients with a previous cesarean delivery. With established hospital safety protocols that dictate close maternal and fetal monitoring, avoidance of prostaglandins, and careful titration of oxytocin infusion when induction agents are needed, spontaneous and induced trial of labor after cesarean delivery are safe and should be offered to most patients with 1 previous low transverse, low vertical, or unknown uterine incision after appropriate evaluation, counseling, planning, and shared decision-making. Future research should focus on clarifying true risk factors and identifying the optimal approach to intrapartum and induction management, tools for antenatal prediction, and strategies for prevention of uterine rupture during trial of labor after cesarean delivery. A better understanding will facilitate patient counseling, support efforts to improve trial of labor after cesarean delivery and vaginal birth after cesarean delivery rates, and reduce the morbidity and mortality associated with uterine rupture during trial of labor after cesarean delivery.

No. 155-Guidelines for Vaginal Birth After Previous Caesarean Birth

OBJECTIVE

To provide evidence-based guidelines for the provision of a trial of labour (TOL) after Caesarean section.

OUTCOME

Fetal and maternal morbidity and mortality associated with vaginal birth after Caesarean (VBAC) and repeat Caesarean section.

EVIDENCE

MEDLINE database was searched for articles published from January 1, 1995, to February 28, 2004, using the key words "vaginal birth after Caesarean (Cesarean) section." The quality of evidence is described using the Evaluation of Evidence criteria outlined in the Report of the Canadian Task Force on the Periodic Health Exam.

RECOMMENDATIONS

VALIDATION: These guidelines were approved by the Clinical Practice Obstetrics and Executive Committees of the Society of Obstetricians and Gynaecologists of Canada.

Effect of gestational age at the prior cesarean delivery on maternal morbidity in subsequent VBAC attempt

OBJECTIVE

The purpose of this study was to estimate the effect of gestational age at the time of prior cesarean on maternal morbidity in women attempting vaginal birth after cesarean delivery (VBAC).

STUDY DESIGN

A retrospective cohort study of women attempting VBAC, comparing women with a prior cesarean delivery < or = 34 completed weeks to women with a prior cesarean delivery > 34 weeks. The primary outcome was maternal morbidity, including uterine rupture. Univariable, stratified, and multivariable analyses were used to estimate the effect of a prior cesarean performed at < or = 34 weeks on maternal morbidities.

RESULTS

Of 19,474 women with 1 prior cesarean, 12,535 attempted VBAC and 508 of those had a previous cesarean < or = 34 weeks. Study groups had similar risks of uterine rupture (adjusted OR [AOR], 1.5; 95% CI, 0.7-3.5; P = .32) and composite morbidity (AOR, 0.9; 95% CI, 0.5-1.8; P = .81).

CONCLUSION

Prior cesarean delivery at < or = 34 weeks' gestation does not appear to increase the risk of maternal morbidity in a subsequent VBAC attempt.

Evidence-based vaginal birth after Caesarean section

Caesarean section rates are rising globally. Whether vaginal birth after Caesarean (VBAC) is safe and under what circumstances is increasingly important. This chapter reviews the literature about the risks of VBAC, patient and management factors that may alter risk, and discusses ongoing research as well as suggestions for improving future research.

Guidelines for Vaginal Birth After Previous Caesarean Birth

OBJECTIVE

To provide evidence-based guidelines for the provision of a trial of labour (TOL) after Caesarean section.

OUTCOME

Fetal and maternal morbidity and mortality associated with vaginal birth after Caesarean (VBAC) and repeat Caesarean section.

EVIDENCE

MEDLINE database was searched for articles published from January 1, 1995, to February 28, 2004, using the key words "vaginal birth after Caesarean (Cesarean) section". The quality of evidence is described using the Evaluation of Evidence criteria outlined in the Report of the Canadian Task Force on the Periodic Health Exam.

RECOMMENDATIONS

1. Provided there are no contraindications, a woman with 1 previous transverse low-segment Caesarean section should be offered a trial of labour (TOL) with appropriate discussion of perinatal risks and benefits. The process of informed consent with appropriate documentation should be an important part of the birth plan in a woman with a previous Caesarean section (II-2B). 2. The intention of a woman undergoing a TOL after Caesarean section should be clearly stated, and documentation of the previous uterine scar should be clearly marked on the prenatal record (II-2B). 3. For a safe labour after Caesarean section, a woman should deliver in a hospital where a timely Caesarean section is possible. The woman and her health care provider must be aware of the hospital resources and the availability of obstetric, anesthetic, pediatric, and operating-room staff (II-2A). 4. Each hospital should have a written policy in place regarding the notification and (or) consultation for the physicians responsible for a possible timely Caesarean section (III-B). 5. In the case of a TOL after Caesarean, an approximate time frame of 30 minutes should be considered adequate in the set-up of an urgent laparotomy (III-C). 6. Continuous electronic monitoring of women attempting a TOL after Caesarean section is recommended (II-2A). 7. Suspected uterine rupture requires urgent attention and expedited laparotomy to attempt to decrease maternal and perinatal morbidity and mortality (II-2A). 8. Oxytocin augmentation is not contraindicated in women undergoing a TOL after Caesarean section (11-2A). 9. Medical induction of labour with oxytocin may be associated with an increased risk of uterine rupture and should be used carefully after appropriate counselling (II-2B). 10. Medical induction of labour with prostaglandin E2 (dinoprostone) is associated with an increased risk of uterine rupture and should not be used except in rare circumstances and after appropriate counselling (II-2B). 11. Prostaglandin E1 (misoprostol) is associated with a high risk of uterine rupture and should not be used as part of a TOL after Caesarean section (II-2A). 12. A foley catheter may be safely used to ripen the cervix in a woman planning a TOL after Caesarean section (II-2A). 13. The available data suggest that a trial of labour in women with more than 1 previous Caesarean section is likely to be successful but is associated with a higher risk of uterine rupture (II-2B). 14. Multiple gestation is not a contraindication to TOL after Caesarean section (II-2B). 15. Diabetes mellitus is not a contraindication to TOL after Caesarean section (II-2B). 16. Suspected fetal macrosomia is not a contraindication to TOL after Caesarean section (II-2B). 17. Women delivering within 18 to 24 months of a Caesarean section should be counselled about an increased risk of uterine rupture in labour (II-2B). 18. Postdatism is not a contraindication to TOL after Caesarean section (II-2B). 19. Every effort should be made to obtain the previous Caesarean section operative report to determine the type of uterine incision used. In situations where the scar is unknown, information concerning the circumstances of the delivery is helpful in determining the likelihood of a low transverse incision. If the likelihood of a low transverse incision is high, a TOL after Caesarean section can be offered (II-2B).

VALIDATION

These guidelines were approved by the Clinical Practice Obstetrics and Executive Committees of the Society of Obstetricians and Gynaecologists of Canada.

Vaginal birth after Caesarean section: review of antenatal predictors of success

OBJECTIVE

To determine antenatal factors that may predict successful vaginal birth after Caesarean (VBAC).

DATA SOURCES

The MEDLINE database was searched for all English-language articles describing the impact of various factors on outcomes when VBAC is attempted. Articles reviewed included published abstracts, retrospective and prospective studies, and meta-analyses. CRITERIA FOR STUDY SELECTION: Studies were included if they reported both a control group of pregnant women without the factor under evaluation and a study group with this factor, both undergoing a trial of labour (TOL). Other criteria included accountability for all individuals enrolled at study outset, and vaginal delivery rates in both study and control groups stated or easily calculated.

RESULTS

A nonrecurrent indication for previous Caesarean section (CS), such as breech presentation or fetal distress, is associated with a much higher successful VBAC rate than recurrent indications, such as cephalopelvic disproportion (CPD). Even with a history of CPD, two-thirds of women will have successful VBAC, though rates decrease with increasing numbers of prior CS. Prior vaginal deliveries are excellent prognostic indicators of successful VBAC, especially if the vaginal delivery follows the prior CS. A low vertical uterine incision does not seem to adversely affect VBAC success rates as compared to a low transverse incision. Maternal obesity and diabetes mellitus adversely affect VBAC outcomes. Fetal macrosomia does not appear to be a contraindication to VBAC, as success rates exceeding 50% are achieved and uterine rupture rates are not increased. Twin gestation does not preclude VBAC. Post-dates pregnancies may deliver successfully by VBAC in greater than two-thirds of cases.

CONCLUSION

There are few absolute contraindications to attempted VBAC. Attempted VBAC will be successful in the majority of attempted cases.

Risk factors for uterine rupture during a trial of labor after cesarean

The rate of vaginal birth among women with a previous cesarean increased from 18.9% in 1989 to 28.3% in 1996. By 1998, the rate had decreased to 26.3% and preliminary data from 1999 suggest that the rate for that year would be even lower (23.4%). It is not known whether that decrease represents a trend related to increasing concern by providers and women about the risk of uterine rupture. Whereas the overall risk of rupture is 1%, our review demonstrates that there is considerable variation of that risk. More than one previous scar, induction of labor, a short interdelivery interval, or a history of postpartum fever during a previous cesarean may increase the risk of a uterine rupture during a trial of labor. However, there does not appear to be an increase in risk associated with low-vertical scars, and a previous vaginal delivery may be somewhat protective. Further delineation of the factors that increase the risk of uterine rupture will permit better prediction of individualized risk and identification of women for whom attempting a vaginal delivery after cesarean represents a safe option.

Elective repeat cesarean delivery versus trial of labor: a meta-analysis of the literature from 1989 to 1999

OBJECTIVE

The aim of this study was to compare a trial of labor with elective repeat cesarean delivery among women with previous cesarean delivery.

STUDY DESIGN

We searched MEDLINE and EMBASE databases from 1989 through 1999 with the following terms: vaginal birth after cesarean delivery, trial of labor, trial of scar, and uterine rupture. We included all controlled trials from developed countries in which the control group had been eligible for a trial of labor. Outcomes of interest were uterine rupture, hysterectomy, maternal febrile morbidity, maternal mortality, 5-minute Apgar score <7, and fetal or neonatal mortality. We computed pooled odds ratios for each outcome.

RESULTS

The search strategy identified 52 controlled studies, 37 of which were excluded because many of the control subjects were not eligible for a trial of labor. Fifteen studies with a total of 47,682 women were included. Uterine rupture occurred more frequently among women undergoing a trial of labor than among those undergoing elective repeat cesarean delivery (odds ratio, 2.10; 95% confidence interval, 1.45-3.05). There was no difference in maternal mortality risk between the 2 groups (odds ratio, 1.52; 95% confidence interval, 0.36-6.38). Fetal or neonatal death (odds ratio, 1.71; 95% confidence interval, 1.28-2.28) and 5-minute Apgar scores <7 (odds ratio, 2.24; 95% confidence interval, 1.29-3.88) were more frequent in the trial of labor group than in the control group. Mothers undergoing a trial of labor were less likely to have febrile morbidity (odds ratio, 0.70; 95% confidence interval, 0.64-0.77) or to require transfusion (odds ratio, 0.57; 95% confidence interval, 0.42-0.76) or hysterectomy (odds ratio, 0.39; 95% confidence interval, 0.27-0.57).

CONCLUSION

A trial of labor may result in small increases in the uterine rupture rate and in fetal and neonatal mortality rates with respect to elective repeat cesarean delivery. Maternal morbidity, including febrile morbidity, and the need for transfusion or hysterectomy may be reduced with a trial of labor.

Vaginal birth after cesarean

Vaginal birth or trial of labor after previous cesarean delivery represents one of the most significant changes in obstetric practice. There are numerous reasons that influence the decision to proceed with either a trial of labor after previous cesarean delivery or elective repeat cesarean delivery. For the majority of women with a previous cesarean delivery, a trial of labor should be encouraged. There are few absolute contraindications. Women with a previous classical uterine incision should not undergo a trial of labor and should be delivered once fetal lung maturity is documented. An attempted trial of labor should not be discouraged in women with a previous low vertical uterine incision, although the patient should be counseled that the evidence as to the risks and benefits of a trial of labor is limited. In those situations where the previous uterine incision is unknown, but suggestive of a classical uterine incision, an argument can be made for elective repeat cesarean delivery once fetal lung maturity is documented. When the history of a uterine incision is unknown and unlikely to be classical, a trial of labor can be attempted after counseling. Close intrapartum management is warranted in this situation. The optimal management of labor in women with a previous low transverse uterine incision who desire a trial of labor with a breech presentation, multiple gestation, orin whom induction of labor is necessary is uncertain; the evidence as to the risks and benefits of a trial of labor is limited and obstetric management should be individualized after counseling. Uterine rupture represents the most catastrophic complication of a trial of labor after previous cesarean delivery. In women suspected of having a uterine scar injury, prompt intervention is necessary to minimize both maternal and neonatal complications. Women who are not successful with a trial of labor require repeat cesarean delivery and appear to be at greatest risk for maternal complications. Identifying those women most likely to be successful with an attempted trial of labor after previous cesarean while also incurring the least maternal and perinatal morbidity and mortality would be ideal. At present, however, there is no sufficiently predictive method to identify those women most likely to benefit from an elective repeat cesarean delivery. The management of labor in women with a previous uterine scar is not low risk. As the number of women who attempt vaginal birth after previous cesarean delivery increases, we should focus on trying to develop reliable methods of identifying women who should and should not undertake a trial of labor after cesarean delivery.

The case for trial of labor in the patient with a prior low-segment vertical cesarean incision

OBJECTIVE

Our purpose was to review recent obstetric literature detailing the subsequent delivery experience of patients with a prior low-segment vertical cesarean incision and to derive recommendations for practice on the basis of this information.

STUDY DESIGN

Ten studies that included information about pregnancy outcome in patients with prior low-segment vertical cesarean operations were retrieved and reviewed from the American obstetric literature since 1981 and from a review of all abstracts presented annually since 1981 to the Society of Perinatal Obstetricians.

RESULTS

Altogether, information about subsequent pregnancy outcome for 382 patients with prior low-segment vertical cesarean delivery was available for analysis. Among the 372 patients with complete patient population information, vaginal delivery was safely accomplished in 306 (82%). Four uterine ruptures (1.05%) have been reported, only one of which occurred after a single prior unextended low-segment vertical cesarean incision. Two ruptures occurred elsewhere on the lateral or posterior aspect of the uterus in subsequent pregnancies, and the fourth rupture occurred at the juncture of prior low vertical and transverse incisions. No perinatal mortality or permanent perinatal morbidity was encountered with these pregnancies.

CONCLUSIONS

In the otherwise uncomplicated pregnancy the patient with one previous nonextended low-segment vertical cesarean incision should be considered to have a prior low-segment scar and as such be a candidate for trial of labor in her current singleton pregnancy. The same care, counseling, and caution should be exercised for this patient as for one with a prior low-segment transverse incision.