Risk factors associated with uterine rupture during trial of labor after cesarean delivery: a case-control study

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.

Trial of labor after cesarean delivery for estimated large for gestational age fetuses: A retrospective cohort study

OBJECTIVE

Although ultrasonographic estimation of fetal weight ≥90th percentile is not associated with a greater risk for uterine rupture, trial of labor after cesarean delivery (TOLAC) is considered relatively contraindicated for macrosomic fetuses. Hence, when an estimated fetal weight of 4000 g is detected, TOLAC is usually avoided.Our aim was to evaluate the obstetrical outcome and safety of TOLAC in women with estimated large for gestational age fetuses (eLGA) (≥90th percentile).

STUDY DESIGN

Our retrospective cohort study encompassed all pregnant women with an estimated fetal weight ≥90th percentile for gestational age, admitted to a single tertiary care center between January 2012-July 2017 for TOLAC.

RESULTS

1949 women met the inclusion criteria; 78 (4%) eLGA and 1871 (96%) controls. Fifty-five (70.5%) women in the study group had experienced a successful vaginal delivery compared to 1506 (80.5%) of the controls (p = 0.03). The rate of obstetrical complications, including scar dehiscence, uterine rupture, a 3rd/4th degree perineal tear or shoulder dystocia were comparable. The rate of post-partum hemorrhage (PPH) increased in the study group compared to the controls (7.7 % vs.1.7%; p = 0.001).

CONCLUSION

TOLAC for eLGA fetuses can be considered safe, however, lower successful rates of vaginal births after a cesarean delivery and an increased PPH rate, may be expected.

Trial of labor after cesarean in primiparous women with fetal macrosomia

KEY MESSAGE

Spontaneous labor onset, epidural anesthesia and prior cesarean for non-arrest disorders are strong predictors of successful vaginal birth after cesarean in women delivering a macrosomic fetus.

PURPOSE

Lower rates of successful vaginal birth after cesarean in association with increasing birthweight were previously reported. We aimed to determine the factors associated with successful trial of labor after cesarean (TOLAC) among primiparous women with fetal macrosomia.

METHODS

A retrospective cohort study conducted during 2005-2019 at two university hospitals, including all primiparous women delivering a singleton fetus weighing ≥ 4000 g, after cesarean delivery at their first delivery. A multivariate analysis was performed to evaluate the characteristics associated with TOLAC success (primary outcome).

RESULTS

Of 551 primiparous women who met the inclusion criteria, 50.1% (n = 276) attempted a TOLAC and 174 (63.0%) successfully delivered vaginally. In a multivariate analysis, spontaneous onset of labor (aOR [95% CI] 3.68 (2.05, 6.61), P < 0.001), epidural anesthesia (aOR [95% CI] 2.38 (1.35, 4.20), P = 0.003) and history of cesarean delivery due to non-arrest disorder (aOR [95% CI] 2.25 (1.32, 3.85), P = 0.003) were the only independent factors associated with TOLAC success. Successful TOLAC was achieved in 82.0% (82/100) in the presence of all three favorable factors, 61.3% (65/106) in the presence of two factors and 38.6% (27/70) in the presence of one or less of these three factors (P < 0.001).

CONCLUSION

Spontaneous onset of labor, epidural anesthesia and prior cesarean delivery due to non-arrest disorders were independently associated with higher vaginal birth after cesarean rate among women with fetal macrosomia, with an overall favorable success rate in the presence of these factors. These findings should be implemented in patient counseling in those contemplating a vaginal birth in this setting.

Risk management of vaginal birth after cesarean section (Review)

The increasing number of patients who desire to experience vaginal birth after cesarean (VBAC) and the optimized protocols for trial of labor after cesarean (TOLAC) has led to a shift of old obstetrical paradigms. The VBAC trend is accompanied with numerous challenges for healthcare professionals, from establishing suitability of each pregnant patient profile for TOLAC to active labor management, and ethical or legal issues, which occasionally are not included in specific guidelines. That is why an individualized risk assessment and management can serve obstetricians as a useful tool for improving outcomes of patients, satisfaction, and also for avoiding legal or moral liabilities. The risk management concept aims to reduce foreseen risks and to emulate strategies for prediction and prevention of unwanted events. In obstetrics, and particularly for the VBAC topic, this concept is relatively new and undefined, and thus its features are disparate between guideline recommendations and clinical studies. This narrative review intends to offer a new and organic perspective over clinical aspects of TOLAC and VBAC risk management.

Time matters-a Swedish cohort study of labor duration and risk of uterine rupture

INTRODUCTION

Uterine rupture is an obstetric emergency associated with maternal and neonatal morbidity. The main risk factor is a prior cesarean section, with rupture occurring in subsequent labor. The aim of this study was to assess the risk of uterine rupture by labor duration and labor management.

MATERIAL AND METHODS

This is a Swedish register-based cohort study of women who underwent labor in 2013-2018 after a primary cesarean section (n = 20 046). Duration of labor was the main exposure, calculated from onset of regular labor contractions and birth; both timepoints were retrieved from electronic medical records for 12 583 labors, 63% of the study population. Uterine rupture was calculated as events per 1000 births at different timepoints during labor. Risk estimates for uterine rupture by labor duration, induction of labor, use of oxytocin and epidural analgesia were calculated using Poisson regression, adjusted for maternal and birth characteristics. Estimates were presented as adjusted rate ratios (ARR) with 95% confidence intervals (CI).

RESULTS

The prevalence of uterine rupture was 1.4% (282/20 046 deliveries). Labor duration was 9.88 hours (95% CI 8.93-10.83) for women with uterine rupture, 8.20 hours (95% CI 8.10-8.31) for women with vaginal delivery, and 10.71 hours (95% CI 10.46-10.97) for women with cesarean section without uterine rupture. Few women (1.0/1000) experienced uterine rupture during the first 3 hours of labor. Uterine rupture occurred in 15.6/1000 births with labor duration over 12 hours. The highest risk for uterine rupture per hour compared with vaginal delivery was observed at 6 hours (ARR 1.20, 95% CI 1.11-1.30). Induction of labor was associated with uterine rupture (ARR 1.54, 95% CI 1.19-1.99), with a particular high risk seen in those induced with prostaglandins and no risk observed with cervical catheter (ARR 1.19, 95% CI 0.83-1.71). Labor augmentation with oxytocin (ARR 1.60, 95% CI 1.25-2.05) and epidural analgesia (ARR 1.63, 95% CI 1.27-2.10) were also associated with uterine rupture.

CONCLUSIONS

Labor duration is an independent factor for uterine rupture among women attempting vaginal delivery after cesarean section. Medical induction and augmentation of labor increase the risk, regardless of maternal and birth characteristics.

Oxytocin use in trial of labor after cesarean and its relationship with risk of uterine rupture in women with one previous cesarean section: a meta-analysis of observational studies

BACKGROUND

Trial of labor after a previous cesarean delivery (TOLAC) has reduced the rate of cesarean sections (CS). Nevertheless, the widespread use of TOLAC has been limited by an increase in adverse outcomes, the most serious one being the risk of symptomatic uterine rupture, which is possibly associated with oxytocin. In this meta-analysis, we explored the risk association between oxytocin use and uterine rupture in TOLAC.

METHODS

Multiple electronic databases (PubMed, Embase, Web of Science, and Google Scholar) were searched for cross-sectional studies reporting on TOLAC, oxytocin and uterine rupture, which were published between January 1986 and October 2019. The bias-corrected Hedge's g was calculated as the effect size using the random-effects model. A two-sample Z test was used to compare the differences in synthetic rates between groups. The Newcastle-Ottawa Scale (NOS) was used to evaluate the risk of bias. Quality of the evidence was assessed with the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) certainty ratings system.

RESULTS

A total of 14 studies, which included 48,457 women who underwent TOLAC, met the inclusion criteria. The pooled rate of vaginal birth after a cesarean section (VBAC) and the rate of uterine rupture in spontaneous labor were 74.3 and 0.7%, respectively. In addition, the pooled rate of VBAC and the rate of uterine rupture in the induction labor group was 60.7 and 2.2%, respectively. The women who had spontaneous labor had a significantly higher rate of VBAC (p = 0.001) and a lower rate of uterine rupture (p = 0.0003) compared to induced labor. The pooled rates of uterine rupture in women using oxytocin and women not using oxytocin in TOLAC were 1.4% and 0.5%, respectively, and the difference was significant (p = 0.0002). Also, the synthetic rate of uterine rupture in oxytocin augmentation among women with spontaneous labor and women who had a successful induction of labor were 1.7% and 2.2%, respectively, without significant difference (p = 0.443).

CONCLUSIONS

Women with induced labor had a higher risk of uterine rupture compared to women with spontaneous labor following TOLAC. Oxytocin use may increase this risk, which could be influenced by the process of induction or individual cervix condition. Consequently, simplified and standardized intrapartum management, precise protocol, and cautious monitoring of oxytocin use in TOLAC are necessary.

ACOG Practice Bulletin No. 205: Vaginal Birth After Cesarean Delivery

Trial of labor after cesarean delivery (TOLAC) refers to a planned attempt to deliver vaginally by a woman who has had a previous cesarean delivery, regardless of the outcome. This method provides women who desire a vaginal delivery the possibility of achieving that goal-a vaginal birth after cesarean delivery (VBAC). In addition to fulfilling a patient's preference for vaginal delivery, at an individual level, VBAC is associated with decreased maternal morbidity and a decreased risk of complications in future pregnancies as well as a decrease in the overall cesarean delivery rate at the population level (). However, although TOLAC is appropriate for many women, several factors increase the likelihood of a failed trial of labor, which in turn is associated with increased maternal and perinatal morbidity when compared with a successful trial of labor (ie, VBAC) and elective repeat cesarean delivery (). Therefore, assessing the likelihood of VBAC as well as the individual risks is important when determining who is an appropriate candidate for TOLAC. Thus, the purpose of this document is to review the risks and benefits of TOLAC in various clinical situations and to provide practical guidelines for counseling and management of patients who will attempt to give birth vaginally after a previous cesarean delivery.

Practice Bulletin No. 184: Vaginal Birth After Cesarean Delivery

Trial of labor after cesarean delivery (TOLAC) refers to a planned attempt to deliver vaginally by a woman who has had a previous cesarean delivery, regardless of the outcome. This method provides women who desire a vaginal delivery the possibility of achieving that goal-a vaginal birth after cesarean delivery (VBAC). In addition to fulfilling a patient's preference for vaginal delivery, at an individual level, VBAC is associated with decreased maternal morbidity and a decreased risk of complications in future pregnancies as well as a decrease in the overall cesarean delivery rate at the population level (1-3). However, although TOLAC is appropriate for many women, several factors increase the likelihood of a failed trial of labor, which in turn is associated with increased maternal and perinatal morbidity when compared with a successful trial of labor (ie, VBAC) and elective repeat cesarean delivery (4-6). Therefore, assessing the likelihood of VBAC as well as the individual risks is important when determining who is an appropriate candidate for TOLAC. Thus, the purpose of this document is to review the risks and benefits of TOLAC in various clinical situations and to provide practical guidelines for counseling and management of patients who will attempt to give birth vaginally after a previous cesarean delivery.

The importance of clinically and ethically fine-tuning decision-making about cesarean delivery

In obstetric practice, each pregnant woman presents with a composite of maternal and fetal characteristics that can alter the risk of significant harm without cesarean intervention. The hospital's availability of resources and the obstetrician's training, experience, and skill level can also alter the risk of significant harm without cesarean intervention. This paper proposes a clinical ethical framework that takes these clinical and organizational factors into account, to promote a deliberative rather than simplistic approach to decision-making and counseling about cesarean delivery. The result is a clinical ethical framework that should guide the obstetrician in fine-tuning his or her evidence-based, beneficence-based analysis of specific clinical and organizational factors that can affect the strength of the beneficence-based clinical judgment about cesarean delivery. We illustrate the clinical application of this framework for three common obstetric conditions: Category II fetal heart rate tracing, prior non-classical cesarean delivery, and breech presentation.

Practice Bulletin No. 173: Fetal Macrosomia

Suspected fetal macrosomia is encountered commonly in obstetric practice. As birth weight increases, the likelihood of labor abnormalities, shoulder dystocia, birth trauma, and permanent injury to the neonate increases. The purpose of this document is to quantify those risks, address the accuracy and limitations of methods for estimating fetal weight, and suggest clinical management for a pregnancy with suspected fetal macrosomia.

Do Women Have a Choice? Care Providers' and Decision Makers' Perspectives on Barriers to Access of Health Services for Birth after a Previous Cesarean

BACKGROUND

Repeat cesarean delivery is the single largest contributor to the escalating cesarean rate worldwide. Approximately 80 percent of women with a past cesarean are candidates for vaginal birth after a cesarean (VBAC), but in Canada less than one-third plan VBAC. Emerging evidence suggests that these trends may be due in part to nonclinical factors, including care provider practice patterns and delays in access to surgical and anesthesia services. This study sought to explore maternity care providers' and decision makers' attitudes toward and experiences with providing and planning services for women with a previous cesarean.

METHODS

In-depth, semi-structured interviews were conducted with family physicians, midwives, obstetricians, nurses, anesthetists, and health service decision makers recruited from three rural and two urban Canadian communities. Constructivist grounded theory informed iterative data collection and analysis.

RESULTS

Analysis of interviews (n = 35) revealed that the factors influencing decisions resulted from interactions between the clinical, organizational, and policy levels of the health care system. Physicians acted as information providers of clinical risks and benefits, with limited discussion of patient preferences. Decision makers serving large hospitals revealed concerns related to liability and patient safety. These stemmed from competing access to surgical resources.

CONCLUSIONS

To facilitate women's increased access to planned VBAC, it is necessary to address the barriers perceived by care providers and decision makers. Strategies to mitigate concerns include initiating decision support immediately after the primary cesarean, addressing the social risks that influence women's preferences, and managing perceptions of patient and litigation risks through shared decision making.

A randomised controlled trial comparing 30 mL and 80 mL in Foley catheter for induction of labour after previous Caesarean section

Inducing labour with a Foley balloon catheter rather than using oxytocin or prostaglandins is considered to be less risky if the uterus is scarred.¹ It is not known if more fluid in the balloon is more effective without being more dangerous. Volumes of 80 mL and 30 mL were compared in 154 eligible women. Mode of delivery, duration of labour and delivery within 24 h were similar in both groups. However, the second group required oxytocin more frequently. Though more scar dehiscences occurred in the first group, the difference was not significant.

Amniotic Sac Herniation Through a Prior Cornual Scar in The Third Trimester

Introduction Uterine rupture occurs in less than 0.1% of pregnancies. This complication can be detrimental to mother and fetus if not detected and managed in a timely manner. We report an unusual presentation of uterine scar rupture that was diagnosed on ultrasound in a completely stable patient with reassuring fetal status. Case Report A 24-year-old Gravida 5, Para 3 with history of cornual resection for ectopic pregnancy and two previous uterine ruptures presented at 30 weeks' gestation with worsening abdominal pain. Ultrasound identified herniation of the amniotic sac with fetal parts. The patient underwent cesarean delivery and cornual defect repair. Conclusion Close observation and early delivery remain vital to the patient's management.

High prevalence of maternal hypothyroidism despite adequate iodine status in Indian pregnant women in the first trimester

BACKGROUND

Iodine requirements are increased during pregnancy to maintain maternal and fetal euthyroidism. There have been recent improvements in iodized salt coverage in India, but whether iodized salt is sufficient to sustain iodine requirements during pregnancy remains uncertain. Our aims were to measure thyroid status in first trimester pregnant women in southern India and assess potential determinants of thyroid function, including iodine status, thyroid autoimmunity, dietary patterns, body weight, and anemia.

METHODS

This was a cross-sectional study among 334 pregnant women of ≤ 14 weeks' gestation, in Bangalore, India. We measured anthropometrics, urinary iodine concentration (UIC), maternal thyroid volume (by ultrasound), and thyroid function. We applied a thyrotropin (TSH) upper limit of 2.5 mIU/L to classify thyroid insufficiency. Using a questionnaire, we obtained sociodemographic and dietary data, obstetric history, and use of iodized salt and iodine supplements.

RESULTS

Among the women, the mean (standard deviation) gestational age was 10.3 (2.5) weeks, 67% were nulliparous, 21% were vegetarian, 19% were anemic, and 23% were overweight or obese. Iodized salt was used by 98% of women, and they were iodine sufficient: median UIC (range) was 184.2 μg/L (8.1-1152 μg/L) and all had a normal thyroid volume. However, 18% of the women had thyroid insufficiency: 3.7% had overt hypothyroidism (83% with positive TPO-Ab), 9.2% had subclinical hypothyroidism, and 5.2% had hypothyroxinemia. Women consuming vegetarian diets did not have significantly lower iodine intakes or higher risk of hypothyroidism than those consuming mixed diets, but overweight/obesity and anemia predicted thyroid insufficiency.

CONCLUSION

In this urban population of southern India, pregnant women have adequate iodine status in the first trimester. Despite this, many have thyroid insufficiency, and the prevalence of overt hypothyroidism is more than fivefold higher than reported in other iodine sufficient populations of pregnant women.

Pregnancy outcome in women with previous one cesarean section

OBJECTIVE

The purpose of this study was to determine the outcome of pregnancy in women with previous one cesarean section in relation to vaginal delivery and maternal and perinatal complications. It also aimed at identifying the factors, which can influence the outcome of trial of scar (TOS).

MATERIALS AND METHODS

A retrospective analysis of medical records of 151 women with previous one cesarean section who delivered at the Mafraq Hospital, Abu Dhabi between January-August 2011was carried out. Those women with previous classical cesarean section and those with extreme prematurity were excluded. The collected data were analyzed using SPSS software version 20. Continuous and categorical data were presented in the form of mean, standard deviation and percentage, while proportions were analyzed using the chi-square test. A p-value ≤0.05 was considered statistically significant.

RESULTS

Of the 151 women, 115 were candidates for TOS. Of them, 96 (83.47%) had vaginal birth after cesarean (VBAC) and 19 (16.5%) had a repeat cesarean section. There were four cases of primary postpartum hemorrhage (PPH) and two cases of scar dehiscence in the study group. No significant perinatal morbidity was observed. VBAC rate was significantly more in women who had prior vaginal deliveries, especially in those with previous VBAC.

CONCLUSION

In carefully selected cases, trial of labour (TOL) after a prior cesarean is safe and often successful. A prior vaginal delivery, particularly, a prior VBAC are associated with a higher rate of successful TOL.

Vaginal birth after cesarean and trial of labor after cesarean: what should we be recommending relative to maternal risk:benefit?

Trial of labor after cesarean (TOLAC) delivery is currently a hot obstetrical topic owing to the acute rise in the rate of cesarean deliveries, both primary and repeat. When the physician and patient are considering TOLAC, several factors should be considered: risk of uterine rupture, contraindications, minimizing risk and morbidity, choosing the appropriate candidate and whether or not to induce. Each patient has her own set of individual risk factors that may decrease her chance of successful vaginal birth after cesarean delivery or increase her risks with TOLAC. Once all things are considered, the risk:benefit of TOLAC should be weighed up before a decision is reached. Each of these factors is discussed in respect to maternal risk:benefit, with the focus on evidence presented in the current literature.

Ultrasound evaluation of uterine scar after cesarean section

INTRODUCTION

The rate of attempted vaginal birth after previous cesarean delivery has decreased, while the success rate of such births increased. Advances in surgical techniques, the development of anesthesiology services, particularly endotracheal anesthesia, very quality postoperative care with cardiovascular, respiratory and biochemical resuscitation, significantly reduce maternal mortality and morbidity after cesarean section. Progress and development of neonatal services, and intensive care of newborns is enabled and a high survival of newborn infants. Complications after cesarean section were reduced, and the introduction of prophylaxis and therapy of powerful antibiotics, as well as materials for sewing drastically reduce all forms of puerperal infection.

GOAL

Goal was to establish a measurement value of the parameters that are evaluated by ultrasound.

MATERIAL AND METHODS

Each of the measured parameters was scored. The sum of points is shown in tables. Based on the sum of points was done an estimate of the scar on the uterus after previous caesarian section and make the decision whether to complete delivery naturally or repeat cesarean section. We conducted a prospective study of 108 pregnant women. Analyzed were: shape scar thickness (thickening), continuity, border scar out, echoing the structure of the lower uterine segment and scar volume

RESULTS

The study showed that scar thickness of 3.5 mm or more, the homogeneity of the scar, scar triangular shape, qualitatively richer perfusion, and scar volume verified by 3D technique up to10 cm are attributes of the quality of the scar.

CONCLUSION

Based on the obtained results we conclude that ultrasound evaluation of the quality of the scar has practical application in the decision on the mode of delivery in women who had previously given birth by Caesarean section.

Risk of uterine rupture in women undergoing trial of labour with a history of both a caesarean section and a vaginal delivery

PURPOSE

To determine the risk of uterine rupture for women undergoing trial of labour (TOL) with both a prior caesarean section (CS) and a vaginal delivery.

METHODS

A systematic literature search was performed using keywords for CS and uterine rupture. The results were critically appraised and the data from relevant and valid articles were extracted. Odds ratios were calculated and a pooled estimate was determined using the Mantel-Haenszel method.

RESULTS

Five studies were used for final analysis. Three studies showed a significant risk reduction for women with both a previous CS and a prior vaginal delivery (PVD) compared to women with a previous CS only, and two studies showed a trend towards risk reduction. The absolute risk of uterine rupture with a prior vaginal delivery varied from 0.17 to 0.46%. The overall odds ratio for PVD was 0.39 (95% CI 0.29-0.52, P < 0.00001).

CONCLUSION

Women with a history of both a CS and vaginal delivery are at decreased risk of uterine rupture when undergoing TOL compared with women who have only had a CS.

Can a vaginal birth after cesarean delivery be a normal labor and birth? Lessons from midwifery applied to trial of labor after a previous cesarean delivery

Women who undergo a trial of labor after a previous cesarean delivery (TOLAC) have special needs prenatally and during the intrapartum period. Counseling about the choice of TOLAC versus an elective repeat cesarean delivery involves complex statistical concepts. Prenatal counseling that is patient centered, individualized, and presented in a way that addresses the health literacy and health numeracy of the recipient encompasses best practices that support patient decision making. Evidence-based practices during labor that support vaginal birth and increase patient satisfaction are of special value for this population.

Uterine Rupture and Septic Peritonitis Following Dystocia and Assisted Delivery in a Great Dane Bitch

A Great Dane bitch was treated for presumed primary uterine inertia with repeated doses of oxytocin and manually assisted whelping. She was diagnosed with uterine rupture and septic peritonitis the following day. The uterine rupture is hypothesized to have occurred as a result of the management strategy used to treat dystocia. The dog underwent ovariohysterectomy, and the septic peritonitis was managed with open peritoneal drainage. The dog recovered well and was discharged 5 days later. No previous reports of canine uterine rupture associated with manual intervention appear to have been published. This report highlights the potential dangers involved in such an approach.

Predicting uterine rupture in women undergoing trial of labor after prior cesarean delivery

Uterine rupture is the most serious complication for women undergoing trial of labor (TOL) after prior cesarean delivery. While rates of uterine rupture vary significantly according to a variety of clinically associated risk factors, the absolute risk for this complication ranges between 0.5 and 4 percent. Previous vaginal delivery and prior successful vaginal birth after cesarean delivery confer the lowest risk of rupture on women attempting TOL. In contrast, multiple prior cesareans, short interpregnancy interval, single layer uterine closure, prior preterm cesarean, labor induction and augmentation have all been suggested in some studies as factors which may increase the rate of uterine rupture. While considering these risk factors is important in counseling women regarding childbirth following cesarean delivery, the infrequency of uterine rupture coupled with relatively weak associations for most risk factors has prevented the development of an accurate prediction tool for uterine rupture. Preliminary studies suggest that sonographic evaluation of the uterine scar may hold some promise for identifying women at risk.

Vaginal birth after cesarean delivery

By 2004, only 9.2% of women in the United States with prior cesareans underwent a term of labor (TOL), although nearly two thirds of these women are actually candidates for a TOL. In this article, the author notes that the principal risk associated with vaginal birth after cesarean delivery (VBAC)-TOL is uterine rupture, which can lead to perinatal death, fetal hypoxic brain injury, and hysterectomy. Risk factors for uterine rupture include number of prior cesareans, prior vaginal delivery, interdelivery interval, and uterine closure technique. The author concludes by noting that a pregnant woman with prior cesarean delivery is at risk for maternal and perinatal complications, whether undergoing TOL or choosing elective repeat operation. Complications of both procedures should be discussed and an attempt made to individualize the risk for uterine rupture and the likelihood of successful VBAC.

Prediction of uterine rupture associated with attempted vaginal birth after cesarean delivery

OBJECTIVE

The purpose of this study was to develop a model that predicts individual-specific risk of uterine rupture during an attempted vaginal birth after cesarean delivery.

STUDY DESIGN

Women with 1 previous low-transverse cesarean delivery who underwent a trial of labor with a term singleton were identified in a concurrently collected database of deliveries that occurred at 19 academic centers during a 4-year period. We analyzed different classification techniques in an effort to develop an accurate prediction model for uterine rupture.

RESULTS

Of the 11,855 women who were available for analysis, 83 women (0.7%) had had a uterine rupture. The optimal final prediction model, which was based on a logistic regression, included 2 variables: any previous vaginal delivery (odds ratio, 0.44; 95% CI, 0.27-0.71) and induction of labor (odds ratio, 1.73; 95% CI, 1.11-2.69). This model, with a c-statistic of 0.627, had poor discriminating ability and did not allow the determination of a clinically useful estimate of the probability of uterine rupture for an individual patient.

CONCLUSION

Factors that were available before or at admission for delivery cannot be used to predict accurately the relatively small proportion of women at term who will experience a uterine rupture during an attempted vaginal birth after cesarean delivery.

Advanced abdominal pregnancy resulting from late uterine rupture

BACKGROUND

Advanced abdominal pregnancy is rare, and one that occurs after uterine rupture with delivery of a viable fetus is exceptional.

CASE

A multiparous patient was admitted at 29 weeks of gestation for conservative management of placenta previa. She complained of intermittent abdominal pain, but repeated assessment suggested that both the patient and the fetus were doing well. At 36 weeks, an abdominal pregnancy was diagnosed with radiological features suggestive of uterine rupture. Laparotomy was performed and a healthy infant was delivered.

CONCLUSION

Fetal viability was achieved in this case of abdominal pregnancy secondary to uterine rupture after close maternal and fetal surveillance.

Risk factors for uterine rupture and neonatal consequences of uterine rupture: a population-based study of successive pregnancies in Sweden

OBJECTIVE

Uterine rupture is a rare but a catastrophic event. The aim of the present study was to explore the risk factors for uterine rupture and associated neonatal morbidity and mortality among a cohort of Swedish women attempting vaginal birth in their second delivery.

DESIGN

Population-based cohort study.

SETTING

Sweden.

POPULATION

A total of 300,200 Swedish women delivering two single consecutive births between 1983 and 2001.

METHODS

Swedish population-based registers were used to obtain information concerning demographics, pregnancy and birth characteristics, and neonatal outcomes. Logistic regression was used to analyse potential risk factors for uterine rupture and risk of neonatal mortality associated with uterine rupture. Odds ratios were used to estimate relative risks using 95% CI.

MAIN OUTCOME MEASURE

Uterine rupture and neonatal mortality in the second pregnancy.

RESULTS

Compared with women who delivered vaginally in their first birth, women who underwent a caesarean delivery were, during their second delivery, at increased risk of uterine rupture (adjusted OR 41.79; 95% CI 29.73-57.00). Induction of labour, high (> or = 4000 g) birthweight, postterm (> or = 42 weeks) births, high (> or = 35 years) maternal age, and short (< or = 164 cm) maternal stature were also associated with increased risk of uterine rupture. Uterine rupture was associated with a substantially increased risk in neonatal mortality (adjusted OR 65.62; 95% CI 32.60-132.08).

CONCLUSION

The risk of uterine rupture in subsequent deliveries is not only markedly increased among women with a previous caesarean delivery but also influenced by induction of labour, birthweight, gestational age, and maternal characteristics.

Can uterine rupture in patients attempting vaginal birth after cesarean delivery be predicted?

OBJECTIVE

This study was undertaken to use multivariable methods to develop clinical predictive models for the occurrence of uterine rupture by using both antepartum and early intrapartum factors.

STUDY DESIGN

This was a planned secondary analysis from a multicenter case-control study of uterine rupture among women attempting vaginal birth after cesarean (VBAC) delivery. Multivariable methods were used to develop 2 separate clinical predictive indices--one that used only prelabor factors and the other that used both prelabor and early labor factors. These indices were also assessed with the use of Receiver operating characteristic curves.

RESULTS

We identified 134 cases of uterine rupture and 665 noncases. No single individual factor is sufficiently sensitive or specific for clinical prediction of uterine rupture. Likewise, the 2 clinical predictive indices were neither sufficiently sensitive nor specific for clinical use (receiver operating characteristic curve [area under the curve] 0.67 and 0.70, respectively).

CONCLUSION

Uterine rupture cannot be predicted with either individual or combinations of clinical factors. This has important clinical and medical-legal implications.

Is gestational age an independent variable affecting uterine scar rupture rates?

OBJECTIVE

To evaluate the influence of gestational age on uterine scar rupture.

METHODS

This was a population-based study of data from Cardiff Births Survey over a 10-year (1990-1999) period. Women with only one previous lower segment caesarean section with singleton uncomplicated pregnancy of 37 or more week's gestation, undergoing trial of vaginal delivery were included. SPSS version 10 was used for statistical analysis. Mann-Whitney, Fisher's exact test and Chi-square tests were used wherever appropriate. Odds ratio (OR) with confidence intervals (CI) was used to quantify the risk. Potential confounding by other factors was controlled using logistic regression and corrected odds ratios with 95% confidence intervals were calculated. The data was analysed separately for induced and spontaneous labours. Primary outcome measure assessed was uterine scar rupture rate. Secondary outcome measures were repeat caesarean section rates, maternal and perinatal mortality and morbidity.

RESULTS

Total sample number was 1620. Eighty percent (n = 1301) of the population went into spontaneous labour and 20% (n = 319) were induced. Successful trial of vaginal birth was accomplished in 60% and trial of scar after estimated date of delivery did not alter this outcome significantly (39.1% versus 43.6%, p > 0.05). We noted an overall scar rupture rate of 0.9% (n = 14) and caesarean section rate of 40.4% (n = 654). Scar rupture rates significantly increased in women who underwent trial of labour after estimated date of delivery (p < 0.001, OR 6.3, CI 1.9-20.2) without a corresponding increase in caesarean section, maternal and perinatal morbidity figures. The influence of gestational age on scar rupture persisted even after controlling for other confounding factors such as birth weight, induction of labour and BMI (corrected OR 1.9, CI 1.1-3.5).

CONCLUSIONS

The overall incidence of scar rupture and success of trial of scar after previous caesarean section in our population was similar to that quoted in the literature. Previous evidence has suggested that it is safe for these women to exceed 40 weeks gestation but our data do not support this.

Vaginal birth after one previous caesarean section in a tertiary institution in Nigeria

Vaginal birth after one previous lower segment caesarean section represents one of the most significant and challenging issues in obstetric practice. A 5-year retrospective study was carried out at the University of Benin Teaching Hospital between January 1999 and December 2003, to determine the incidence, the maternal and fetal outcome following vaginal delivery after one previous caesarean section with a view to evaluating its safety and efficacy. There were 5234 deliveries, with 395 cases of one previous caesarean section, giving an incidence of 7.5%. The incidences of emergency caesarean section, elective caesarean section and spontaneous vaginal delivery following trial of vaginal delivery were 34.7%, 9.4% and 48.1%, respectively. During the study period there were 1317 cases of caesarean section, giving an incidence of 25.2% caesarean section rate. The incidence of one previous section among all caesarean section births was 30%. The major morbidity following vaginal delivery was uterine rupture with an incidence of 1.5% and hysterectomy of 0.8%. Three of the uterine ruptures occurred before admission because the patients laboured at home. One maternal death occurred as a result of uterine rupture and postpartum haemorrhage, giving a maternal mortality ratio of 19/100,000 and a case fatality rate of 0.3%. The corrected perinatal mortality rate was 15.2/1000, mainly from obstructed labour, abruptio placenta and fetal distress. Both maternal and fetal mortalities from vaginal birth after one previous section were significantly less than the respective overall maternal and fetal mortality from the institution. The 1-minute apgar score of babies delivered by elective section was significantly (P < 0.001) higher than the apgar score of babies delivered by emergency section and vaginally. There was only one patient with wound dehiscence at elective section without associated perinatal death. Vaginal delivery following caesarean section is relatively safe. However, women in developing countries will continue to require counselling to counter the myths of aversion to operative delivery even at the expense of losing their lives. Our hospitals should have adequate monitoring equipment for high-risk pregnancies so that patients and their babies can be assured of survival.

Uterine rupture after induction of labour in women with previous caesarean section

BACKGROUND

The issues related to safety of induction of labour in women with previous caesarean section remain controversial. The main adverse outcome fuelling this debate is a "small" risk of uterine rupture that is potentially devastating for both the mother and the fetus.

OBJECTIVE

To estimate the risk of uterine rupture or dehiscence in women who require induction of labour with previous caesarean sections.

DESIGN

Five year retrospective review of computerised hospital records and case note review of index cases.

SETTING

Large inner city teaching hospital.

POPULATION

Two hundred and five women who had their labour induced with history of one lower segment caesarean section.

METHODS

This study was conducted at Liverpool Women's Hospital, a tertiary referral centre, with approximately 6000 births per annum. We searched the hospital's computerised records of deliveries from June 1997 to June 2002 and reviewed all indications and outcomes of induction of labour in women with one previous caesarean section. Women with singleton pregnancy and cephalic presentation were then divided into three groups: those with one previous caesarean section and no previous vaginal deliveries, those whose last delivery was a caesarean section but had delivered vaginally before and those whose last delivery was by vaginal route, but had had one caesarean section in the past.

MAIN OUTCOME MEASURES

Uterine rupture or dehiscence, adverse neonatal outcome.

RESULTS

Two hundred and five women were included. There were four cases of uterine rupture and one dehiscence (2.4%, 95% CI 0.8-5.6%). Two babies were profoundly acidotic at birth, but all five neonates were healthy when discharged from hospital with no long term morbidity. All five cases occurred in the group of women with no previous vaginal deliveries. The intrauterine pressure catheter recordings had contributed to the diagnosis of uterine rupture/dehiscence in three out of five cases.

CONCLUSION

In women with previous caesarean section and no vaginal deliveries, induction of labour carries a relatively high risk of uterine rupture/dehiscence despite all precautions, including intrauterine pressure monitoring.

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.

Modified Bishop's score and induction of labor in patients with a previous cesarean delivery

OBJECTIVES

The purpose of this study was to evaluate the association between preinduction modified Bishop's score and obstetric outcome, including successful vaginal birth after prior cesarean (VBAC) and uterine rupture in patients with a previous cesarean undergoing induction of labor.

STUDY DESIGN

Medical records of all patients who had an induction of labor after a previous cesarean in our institution between 1988 and 2002 were reviewed. Patients were divided into 4 groups according to the modified Bishop's score (0 to 2, 3 to 5, 6 to 8, and 9 to 12). The rates of successful VBAC, symptomatic uterine rupture, and other obstetric outcomes were evaluated in each group. Multivariate regression analyses were performed to adjust for confounding factors.

RESULTS

Out of 685 women included in the study, 187 (27.3%) had a modified Bishop's score <2, 276 (40.3%) of 3 to 5, 189 (27.6%) of 6 to 8, and 33 (4.8%) of 9 to 12. The rate of successful VBAC significantly correlated with the modified Bishop's score (57.5%, 64.5%, 82.5%, and 97.0%, respectively, P < .001). However, the rate of uterine rupture was not statistically significant between the groups (2.1%, 1.8%, 0.5%, 0.0%, P=.48). After adjusting for confounding variables, a modified Bishop's score >/=6 remained associated with successful VBAC (odds ratio [OR] 2.07, 95% CI 1.28-3.35, P < .001).

CONCLUSION

The modified Bishop's score before induction of labor is an independent factor associated with successful VBAC.

Results of the National Study of Vaginal Birth After Cesarean in Birth Centers

OBJECTIVE

Some women wish to avoid a repeat cesarean delivery and believe that a midwife-supported vaginal birth after cesarean (VBAC) in a nonhospital setting represents their best chance to do so; there is a small, persistent demand for out-of-hospital VBACs. We conducted a study to obtain the data necessary to formulate an evidence-based policy on this practice.

METHODS

We prospectively collected data on pregnancy outcomes of 1,913 women intending to attempt VBACs in 41 participating birth centers between 1990 and 2000.

RESULTS

A total of 1,453 of the 1,913 women presented to the birth center in labor. Twenty-four percent of them were transferred to hospitals during labor; 87% of these had vaginal births. There were 6 uterine ruptures (0.4%), 1 hysterectomy (0.1%), 15 infants with 5-minute Apgar scores less than 7 (1.0%), and 7 fetal/neonatal deaths (0.5%). Most fetal deaths (5/7) occurred in women who did not have uterine ruptures. Half of uterine ruptures and 57% of perinatal deaths involved the 10% of women with more than 1 previous cesarean delivery or who had reached a gestational age of 42 weeks. Rates of uterine rupture and fetal/neonatal death were 0.2% each in women with neither of these risks.

CONCLUSION

Despite a high rate of vaginal births and few uterine ruptures among women attempting VBACs in birth centers, a cesarean-scarred uterus was associated with increases in complications that require hospital management. Therefore, birth centers should refer women who have undergone previous cesarean deliveries to hospitals for delivery. Hospitals should increase access to in-hospital care provided by midwife/obstetrician teams during VBACs.

LEVEL OF EVIDENCE

III.

Systematic review of the incidence and consequences of uterine rupture in women with previous caesarean section

OBJECTIVE

To evaluate the incidence and consequences of uterine rupture in women who have had a delivery by caesarean section.

DESIGN

Systematic review.

DATA SOURCES

Medline, HealthSTAR, Cochrane Database of Systematic Reviews, Cochrane Controlled Trials Register, National Centre for Reviews and Dissemination, reference lists, and national experts. Studies in all languages were eligible if published in full.

REVIEW METHODS

Methodological quality was evaluated for each study by using criteria from the United States Preventive Services Task Force and the National Health Service Centre for Reviews and Dissemination. Uterine rupture was categorised as asymptomatic or symptomatic.

RESULTS

We reviewed 568 full text articles to identify 71 potentially eligible studies, 21 of which were rated at least fair in quality. Compared with elective repeat caesarean delivery, trial of labour increased the risk of uterine rupture by 2.7 (95% confidence interval 0.73 to 4.73) per 1000 cases. No maternal deaths were related to rupture. For women attempting vaginal delivery, the additional risk of perinatal death from rupture of a uterine scar was 1.4 (0 to 9.8) per 10,000 and the additional risk of hysterectomy was 3.4 (0 to 12.6) per 10 000. The rates of asymptomatic uterine rupture in trial of labour and elective repeat caesarean did not differ significantly.

CONCLUSIONS

Although the literature on uterine rupture is imprecise and inconsistent, existing studies indicate that 370 (213 to 1370) elective caesarean deliveries would need to be performed to prevent one symptomatic uterine rupture.

Vaginal birth following two cesarean deliveries--are the risks exaggerated?

BACKGROUND

Prior to 1996, most women who had undergone two previous cesarean deliveries were offered only cesarean delivery at Al-Hasa Health Centre. A policy of trial of labor was instituted in 1996. We compared the outcome of trial of labor versus cesarean delivery in women with a history of two previous cesarean deliveries who delivered between 1997 and 2002.

PATIENTS AND METHODS

All patients with a history of two previous lower segment cesarean deliveries were included in the study. Those considered suitable were permitted a trial of labor that was neither induced nor augmented at any stage.

RESULTS

Of the 205 patients in the study, 66 delivered vaginally (32.2%), 68 had an emergency cesarean delivery (33.2%), and 71 an elective cesarean delivery (34.6%). No scar dehiscence was observed, nor was hysterectomy performed in either group. The rate of complications was lower in the vaginal delivery group (4.5%) than in the cesarean delivery group (19.4%).

CONCLUSION

Trial of labor in women with a history of two cesarean deliveries is a reasonable consideration, and when carried out without the use of oxytocics or prostaglandins, is associated with reduced maternal morbidity with no difference in perinatal morbidity.

Twin-to-twin transfusion syndrome complicated by spontaneous mid-trimester uterine rupture

Twin-to-twin-transfusion syndrome (TTS) is a serious complication in about 15% of monochorionic twin pregnancies. In severe TTS, the anemic pump twin (donor) develops anhydramnios and the hypervolemic recipient tense polyhydramnios, which often first calls attention to the condition. The most common problems of TTS are fetal complications such as single or double intrauterine demise, spontaneous abortion, prematurity due to uterine distension leading to contractions, preterm rupture of membranes and ultimately neurological impairment. We report a pregnancy with TTS in which rapid development of polyhydramnios led to rupture of a scarred uterus at 19 weeks' gestation. To the best of our knowledge, this is the first report of a potentially lethal maternal complication of TTS.

Fetal Heart Rate Changes Associated With Uterine Rupture

OBJECTIVE

To identify fetal heart rate characteristics of patients with uterine rupture compared with successful vaginal birth after cesarean (VBAC) controls.

METHODS

This is a case-control study. Obstetric records of patients at the University of Washington Medical Center and Swedish Medical Center were reviewed for cases of uterine rupture. Entry criteria included operative confirmation of the diagnosis, gestational age beyond 24 weeks, presence of one or more prior low transverse uterine incisions, and availability of fetal heart tracings. Each case was matched with 3 controls randomly selected from a pool of successful VBAC deliveries at the same institution within 1 year. Three blinded independent examiners then examined fetal heart tracings. Each tracing was rated for the presence of fetal tachycardia, mild or moderate variable decelerations, severe variable decelerations, late decelerations, prolonged decelerations, fetal bradycardia, and loss of uterine tone in both the first and second stages of labor separately.

RESULTS

Of the 48 uterine ruptures identified, 36 met inclusion criteria. These were matched with 100 controls. Cases showed significantly increased rates of fetal bradycardia than controls in the first stage (P <.01) and second stage (P <.01). No significant differences were noted in rates of mild or severe variable decelerations, late decelerations, prolonged decelerations, fetal tachycardia, or loss of uterine tone.

CONCLUSION

Fetal bradycardia in the first and second stage is the only finding to differentiate uterine ruptures from successful VBAC patients.

LEVEL OF EVIDENCE

II-2

VBAC: safety for the patient and the nurse

During the 1970s and 1980s, some women fought for the opportunity to deliver vaginally after a cesarean birth (VBAC). The American College of Obstetricians and Gynecologists initially supported VBAC for many low-risk women. Interventions increased and complications of VBAC were reported, however, and recommendations changed. VBAC should be performed in hospitals equipped to care for women at high risk. Nurses caring for patients undergoing VBAC should be able to recognize and respond to the signs and symptoms of uterine rupture, including the most common symptom, which is a nonreassuring fetal monitor tracing. Nurses also should be aware of the necessity for 24-hour blood banking, electronic fetal monitoring, on-site anesthesia coverage, and continuous presence of a surgeon.

[Perinatal mortality associated factors in a general hospital of Chiapas, Mexico]

OBJECTIVE

To identify socioeconomic, gynecological-obstetric and fetal factors associated with perinatal mortality.

METHODS

A matched case-control study was carried out. Cases were newborns (born live or dead) that were born and died between 28 weeks gestation and 7 days of life. Controls were live newborns between 28 weeks gestation and 7 days of life. A total of 99 cases and 197 controls were studied. Data were obtained from the corresponding medical charts. Statistical analysis was performed using Stata 6.0 software.

RESULTS

Mean maternal age was 24.82 years and mean newborn age was 37.78 weeks gestation with an average birth weight of 2,760 grams. Factors associated with perinatal mortality were: father's occupation as a farmer (adjusted odds ratio (OR)=3.31; 95% CI=1.26-8.66); high obstetric risk index (adjusted OR=10.57; 95% CI=2.82-39.66), cesarean birth (adjusted OR=2.75; 95% CI=1.37-5.51), five or more prenatal visits (adjusted OR=4.43; 95% CI=1.86-10.54) and preterm fetal maturity indices (PEG, APG, GEG) (adjusted OR=9.20; 95% CI=4.39-19.25).

CONCLUSIONS

The risk factors associated with perinatal mortality found in the study are consistent with the findings reported in the international literature. These results show that prevention and control measures should be implemented to identify at risk pregnant women in order to lower perinatal mortality.

Trial of labour after two or three previous caesarean sections

OBJECTIVE

To investigate the safety of a trial of labour (TOL) after two or three previous caesarean sections.

STUDY DESIGN

Retrospective analysis of medical records of women with a history of more than one previous caesarean section who gave birth during a 10-year period (1988-1997) in two large university hospitals in The Netherlands.

RESULTS

Women numbering 30,132 gave birth with a hospital caesarean birth rate of 14.8%. There were 246 women with a history of more than one previous caesarean section: 187 (76%) delivered by elective repeat caesarean section (ERCS); 59 (24%) had a trial of labour, of whom 49 (83%) had a vaginal birth. Three uterine ruptures occurred after previous lower segment caesarean sections without maternal or perinatal mortality related to the uterine rupture; only one rupture was during a trial of labour. In the study group there was no maternal mortality. Maternal morbidity did not differ between women with an elective repeat caesarean or a failed trial of labour. Perinatal mortality was not related to the mode of delivery.

CONCLUSION

Elective repeat caesarean section is not the only answer to a woman with two or three previous caesarean sections. A trial of labour can be a safe option for a selected group of women.

Maternal and perinatal complications with uterine rupture in 142,075 patients who attempted vaginal birth after cesarean delivery: A review of the literature

OBJECTIVE

The purpose of this study was to determine the rate of uterine rupture and its complications as the result of trial of labor after previous cesarean delivery.

STUDY DESIGN

PubMed was searched from 1989 to 2001, with the terms "VBAC, uterine rupture," "trial of labor, uterine rupture," "cesarean delivery, uterine rupture," and "scarred uterus, rupture." For inclusion, reports had to contain data from at least 100 patients with trials of labor that included a description of adverse outcomes. Duplicate reporting from a single institution was excluded. Odds ratios and 95% CIs were calculated.

RESULTS

Seventy-two of the 361 articles (20%) that were identified met the inclusion criteria. A 6.2 per 1000 trial of labor rate of uterine rupture (total=880 uterine ruptures in 142,075 trials of labor) was determined. For every 1000 trials of labor the uterine rupture-related complication rate was 1.8 for packed red blood cell transfusion, 1.5 for pathologic fetal acidosis (cord pH<7.00), 0.9 for hysterectomy, 0.8 for genitourinary injury, 0.4 for perinatal death, and 0.02 for maternal death. The perinatal mortality rate was significantly lower among studies from the United States versus other countries (0.3 vs 0.6; odds ratio, 0.50; 95% CI, 0.26-0.94) and in series that exceeded 1000 patients (0.2 vs 1.7; odds ratio, 7.34; 95% CI, 3.94-13.69).

CONCLUSION

Although relatively uncommon, uterine rupture is associated with several adverse outcomes, depending on the time of the publication and the site and size of the population that was studied.

Uterine rupture during VBAC trial of labor: risk factors and fetal response

For the woman with a prior uterine scar, neither repeat elective cesarean birth nor vaginal birth after cesarean birth (VBAC) trial of labor (TOL) is risk-free. When VBAC-TOL is successful, it is associated with less morbidity than repeat cesarean birth. However, when VBAC-TOL fails due to uterine rupture, severe consequences often ensue. The challenge for clinicians today is to provide women who desire TOL after cesarean birth, a more individualized risk assessment of uterine rupture, thereby enhancing success and optimizing outcome. This article examines major risk factors for uterine rupture during VBAC-TOL. In addition, fetal response to uterine rupture and neonatal outcomes are reviewed.

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.