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ORIGINAL ARTICLE Table of Contents  
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Vaginal birth after cesarean score for the prediction of successful vaginal birth after cesarean section – A prospective observational study

1 Department of Obstetrics and Gynaecology, All India Institute of Medical Sciences, New Delhi, India
2 Department of Obstetrics and Gynaecology, Hamdard Institute of Medical Sciences and Research, New Delhi, India
3 Department of Preventive and Social Medicine, Hamdard Institute of Medical Sciences and Research, New Delhi, India

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Date of Submission25-Jun-2022
Date of Decision16-Jul-2022
Date of Acceptance16-Jul-2022
Date of Web Publication31-Oct-2022


Aim: The aim of this study was to evaluate the demographic and obstetrical factors affecting the chances of vaginal birth after cesarean (VBAC) delivery and to develop a scoring system for the prediction of same. Materials and Methods: It was a prospective observational study done over a period of 1 year. A total of 100 term pregnant women with previous one lower-segment cesarean section (LSCS) fulfilling the criteria for a trial of labor were recruited for the study. As 23 patients refused to undergo trial of labor after cesarean (TOLAC) in early labor, 77 women formed the study group. Parameters assessed to predict successful TOLAC were maternal age, body mass index (BMI), history of prior vaginal delivery, interdelivery interval, indication of previous cesarean section, gestational age, type of labor, Bishop's score, and expected baby weight. Scores 0–2 were given, and the mean score obtained was correlated with the outcome of TOLAC. Results: Successful vaginal delivery occurred in 57.14% (44/77) of women. BMI ≤30 kg/m2 (P = 0.004), parity ≤ 3 (P = 0.005), Bishop's score >4 (P = 0.000), spontaneous onset of labor at the time of admission (P = 0.001), and nonrecurrent indication of previous LSCS (P = 0.029) were found to be significantly associated with the VBAC. The probability of having a successful VBAC was 83.3% and 100%, with the VBAC score value of more than 18 and 20, respectively. Conclusion: The mean VBAC score of 18–20 by the current scoring system is beneficial in predicting the outcome. This can help in counseling the patient, relatives as well as health professionals to undergo labor trial to decrease the cesarean section rate in the current era.

Keywords: Lower-segment cesarean section, scoring, trial of labor, vaginal birth after cesarean

How to cite this URL:
Varun N, Nigam A, Gupta N, Mazhari F, Kashyap V. Vaginal birth after cesarean score for the prediction of successful vaginal birth after cesarean section – A prospective observational study. Indian J Med Spec [Epub ahead of print] [cited 2023 Feb 1]. Available from: http://www.ijms.in/preprintarticle.asp?id=360049

  Introduction Top

The ever-increasing rate of cesarean delivery all over the world has focused the attention on the vaginal birth after cesarean (VBAC). Chief concerns during trial of labor after cesarean (TOLAC) are the risk of uterine rupture, fetal demise, and maternal morbidity. The fear of these complications had contributed to the increased cesarean section rates as well as decreased TOLAC section. There is a general consensus among various associations including the National Institute for Health and Care Excellence, Royal College of Obstetricians and Gynaecologists, American College of Obstetricians and Gynecologists, and National Institutes of Health that a well-planned VBAC is a safe choice for the patients with single previous lower-segment cesarean section (LSCS).[1] This strategy is supported by the health economic modeling.[2] It can also limit the rate of repeat cesarean sections and the maternal morbidity associated with multiple cesarean deliveries.[3],[4],[5]

There are several factors that predict the chances of successful TOLAC, which include age, gestational age, Bishop's score, body mass index (BMI), type of labor, prior vaginal delivery, and expected fetal weight, but their importance becomes very less if considered in isolation. Therefore, there is a felt need to develop a score considering all these parameters together to predict the success of TOLAC.

Most of the studies on the success or failure rate of TOLAC are from developed countries[6] and that data cannot be extrapolated in developing countries like India having a different ethnicity, body constitution, and health facilities. Thus, the present study was done to find out the various factors affecting the TOLAC outcome in isolation as well as in combination and to develop a predictive scoring system to assess the success rate of TOLAC.

The aim of this study was to evaluate the demographic and obstetrical factors affecting the chances of VBAC and to develop a specific prediction score for the same.

  Materials and Methods Top

Type of study

This was a prospective observational study.


The study duration was 1 year.


All pregnant women with one previous LSCS at more than 36 weeks of gestation, who fulfilled the inclusion criteria, were recruited from the antenatal outpatient department after detailed history and examination. Ethical clearance was taken from the institutional ethics committee. Written informed consent was obtained from all the subjects before their participation in the study. Inclusion criteria included singleton pregnancy, cephalic presentation, and no cephalopelvic disproportion. Exclusion criteria included previous two LSCS, malpresentation, previous myomectomy, placenta previa (antepartum hemorrhage), previous classical cesarean section, and women not willing for TOLAC.

A predesigned pretested proforma for data collection was used where demographic and clinical data were recorded for all the participants. A specific scoring table [Table 1] was made in the proforma having 11 demographic and obstetrical variables. VBAC score for each participant was calculated from these variables. To calculate the score, all these variables were assigned a score ranging between 0 and 2, where 0 was the lowest and 2 was the highest probability. Correlation between VBAC score and the outcome in the form of mode of delivery was taken out. The calculated probabilities for successful TOLAC were given a maximum score of 22.
Table 1: Vaginal birth after cesarean delivery scoring system

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All the women for TOLAC were monitored during labor for:

  1. Maternal vital charting every half hour, i.e., pulse rate (PR) and blood pressure
  2. Fetal heart rate (FHR) monitoring (intermittent auscultation every 15 min in the first stage and every 5 min after a contraction in the second stage of labor) as per recent World Health Organization recommendations on intermittent FHR auscultation during labor[7]
  3. Every auscultation lasted for 1 min, and if FHR was not within the normal range (110–160 beats per min), then auscultation was prolonged and covered at least 3 uterine contractions
  4. Patients were monitored for uterine contractions, cervical dilatation, and effacement, the status of liquor and scar tenderness
  5. Whenever needed cardiotocography was used for monitoring

Scar dehiscence was suspected in the presence of maternal tachycardia, scar tenderness, hematuria, or fetal distress or vaginal bleeding. TOLAC was abandoned if there was any suspicion of scar dehiscence, unsatisfactory progress of labor, or fetal distress.

Statistical analysis

All the data were entered in a Microsoft Excel worksheet, and SPSS version 20 (Armonk, NY: IBM Corp). was used for analysis. Data were analyzed descriptively and Chi-square test was used to know the association between dependent and independent variables. In this study, 95% confidence interval and P < 0.05 were considered statistically significant.

  Results Top

The total number of deliveries during the study period of 1 year was 1973. Out of this, there were 536 cesarean sections, making a cesarean section rate of 27.16%. A total of 100 patients were enrolled in the present study and out of that 23 patients refused to undergo VBAC in early labor, so finally 77 were included in the study. The study group was further divided into two groups according to the mode of delivery:

  • Group 1: Vaginal delivery group (44/77)
  • Group 2: Cesarean group (33/77).

The success rate for TOLAC was 57.14% (44/77). Demographic profiles of both the groups were comparable regarding age (21–40 years), parity (1–3), period of gestation (35–41 weeks), birth weight (2.2–4.8 kg), interconceptional period (4–10 years), and history of postoperative fever in the previous pregnancy.

In Group 1, 90.90% (40/44) were spontaneous vaginal delivery and the remaining 9.09% (4/44) were assisted vaginal delivery. In Group 2, the main indication of LSCS was scar tenderness 36.36% (12/33), but only 3 patients had evidence of scar dehiscence intraoperatively. The remaining were in view of fetal distress (24.24%), failed induction (15.15%), meconium-stained liquor (9.09%), abruption (9.09%), and nonprogress of labor (6.06%).

[Table 2] delineates the relationship of demographic parameters in two groups, and BMI <30 kg/m2 and low parity had a significant association with successful TOLAC.
Table 2: Relationship of demographic parameters with vaginal birth after cesarean delivery

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We have found that the chances of VBAC increase in patients who had previous LSCS in view of nonrecurrent indications such as fetal distress, meconium-stained liquor in early labor, and breech presentation (P = 0.029). 84.09% (37/44) of patients in the vaginal delivery group had previous LSCS in view of nonrecurrent indications.

Only 16.8% (13/77) of women had a history of previous vaginal delivery, and out of these, 76.13% (10/13) of women had VBAC and only 23.07% (3/13) had repeat LSCS.

Among Group 1, 88.63% (N = 39/44) of patients had Bishop's score of more than 4 as compared to 30.30% (N = 10/33) of women in Group 2. This finding was clinically significant (Chi-square statistic 27.72 and P < 0.001).

A significant correlation was found between the mode of delivery and the spontaneous onset of labor (Chi-square statistic 18.9887, P < 0.001). In Group 1, 75% (33/44) of patients had spontaneous labor at the time of admission as compared to only 27.27% (n = 9/33) of patients in Group 2. Nine patients in Group 1 were induced and 2 received oxytocin augmentation in Group 1, whereas 23 patients were induced and 1 received augmentation in Group 2.

Five variables were found to be independently associated with successful TOLAC, i.e., BMI, type of labor, parity, an indication of previous LSCS, and Bishop's score.

Among the complications encountered, there was no statistically significant association found. In Group 1, the following complications were seen postpartum hemorrhage (PPH) (2/44), postoperative fever (2/44), and wound sepsis (1/44) and two patients required blood transfusion. In Group 2, there were three cases of scar dehiscence, all were partial, and baby outcome was favorable in all the patients. Other complications included PPH (1/33), postoperative fever (3/33), and wound sepsis (1/33) and two patients received blood transfusion.

After studying all the parameters independently, VBAC score was calculated with 11 parameters in consideration as discussed for all the subjects. The mean total score for patients in Groups 1 and 2 was 17.13 ± 2.35 and 14.30 ± 2.77, respectively. The mean total score for Group 1 was significantly higher than Group 2 and was found to be significantly correlated with the outcome in the form of mode of delivery (P < 0.00001).

The probability of having successful VBAC according to the VBAC score is delineated in [Figure 1]. The probabilities of VBAC success increase with the increasing total score value; women with a score value >14 had a probability of 66.1% to deliver vaginally (VBAC), while women with a score value >20 had a probability of 100% to deliver vaginally (VBAC).
Figure 1: Successful VBAC rate according to the score value. VBAC: Vaginal birth after cesarean

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The present study found no association between the interdelivery interval (P = 0.251), expected birth weight (P = 0.853), gestational age (P = 0.198), history of vaginal delivery (P = 0.285), and history of postoperative fever (P = 0.529) with the mode of present delivery.

  Discussion Top

Cesarean section is one of the most common major surgical procedures performed all over the world. Its incidence is continuously rising because of various reasons, but the primary reason is the increasing rate of primary cesarean section and decreased subsequent TOLAC.[8] According to NFHS-4,[9] the cesarean section rate in India is 28.2% in urban areas and 12.8% in rural areas. The overall cesarean section rate has doubled in the last one decade, i.e., 8.5% in 2005–2006 (NFHS-3) to 17.2% in 2015–2016.[9] It has also been observed that cesarean section rate has a regional bias in India, i.e., 5.8% in Nagaland to 58% in Telangana.[9]

VBAC is the safest option in the properly selected patients to reduce the rising rate of cesarean section.[10] VBAC is associated with shorter hospital stay, less blood loss, less infections, and less thromboembolic events.[11]

The TOLAC success rate was 57.14% in this study which is comparable to other studies. Madaan et al.[1] reported a TOLAC success rate of 53.6% from a tertiary care center from Delhi. The majority of studies from the developed world have shown a 60%–80% success rate of TOLAC as compared to studies from the developing world which have shown a varied success rate of TOLAC, i.e., 42.4% in South Africa, 41.7% in Saudi Arabia, and 60% in India.[2],[4],[12]

Various demographic and obstetric variables affect the successful outcome of TOLAC as evident from the current study. BMI is one of the significant parameters to assess the success of TOLAC. 58.82% of patients with BMI ≤30 kg/m2 had successful TOLAC in our study which is comparable to the results published by Bangal et al.[8] The reason of obese patients having less success rate may be the increased association of other comorbidities with raised BMI, i.e., diabetes and hypertension.

Chances of successful TOLAC increase with previous cesarean section done for nonrecurring indication as evident from the current study (66.1%). Similar results were shown by Madaan et al.,[1] where the success rate ranging from 61 to 67% was reported for various nonrecurring indications, thus emphasizing that one must counsel the women to undergo TOLAC in presence of nonrecurrent indications. Narang et al.[13] showed a success rate of 86.9% when previous LSCS was done for nonrecurrent indication other than cephalopelvic disproportion or dystocia.

VBAC group was more likely to have low parity (≤3) as compared to repeat LSCS group. 97.7% of patients in a VBAC group had low parity (≤3). Similar results were shown by Zaitoun et al.;[11] 90.2% of patients in a VBAC group had low parity (≤3).

Higher Bishop's score (>4) has been found to be the best predictor of the successful TOLAC in the current study which was shown by various other authors also. Zaitoun et al.[11] showed an 88.1% success rate with Bishop's score ≥ 4 (2013). Narang et al.[13] showed a success rate of 53.4% with Bishop's score of more than 7. Contrary to the above studies, Bangal et al.[8] showed a success rate of 94% with Bishop's score between 10 and 13 as compared to a 61.25% success rate with Bishop's score 6–9.

In the present study, success of TOLAC was quite high (78.6%) in women presenting with spontaneous labor as compared to lower success rate (57.8%) shown by Madaan et al.[1] and Narang et al.[13] (54.54%).

This study found no association between the maternal age, interdelivery interval, birth weight, gestation, and history of vaginal delivery with the mode of present delivery, but in many previous studies, they have been shown as a significant parameter. Reason can be the small sample size of the study population.[1],[11],[12],[13] In the previous studies, it has been shown that the history of previous vaginal delivery is a significant parameter to assess the success of VBAC, but in our study, 83.11% (64/77) of patients had no history of previous vaginal delivery, and therefore, it is very difficult to comment on the relationship between mode of present delivery and history of previous vaginal delivery before or after previous LSCS.

Five variables were found to be independently associated with the successful VBAC, Bishop's score (≥4), BMI (≤30 kg/m2), type of labor (spontaneous labor), indication of previous cesarean section (nonrecurrent indication), and parity (≤3). Results were comparable with other studies.[1],[8],[10],[11],[12],[13]

The present study has devised a scoring system that could predict the chances of successful VBAC with reasonable accuracy. The score was developed on the basis of the success rate of variables in predicting successful VBAC. This predictive model can be applied at the time of admission to labor room. Each of the 11 variables was assigned a score from 0 to 2 and maximum score was 22. The probabilities of VBAC success increase with increasing total score value; women with a score >14 and 20 have a probability of 66.1% and 100%, respectively, to deliver vaginally. This VBAC scoring if properly implemented will increase the VBAC rates in clinical practice.

Multiple researchers have devised various prediction models based on different clinical factors that can help the obstetrician to improve the accuracy to predict the likelihood of VBAC. These predictive models can be applied during early pregnancy, late pregnancy, or during labor to predict the birth outcome. We have compared all the available prediction models [Table 3], with our model in terms of advantages, disadvantages, and feasibility of application. VBAC scoring table developed by the current study is accurate and simple to use and included all the parameters of significance. Application of scoring system can reduce the increasing cesarean section rates in the current clinical practice.[22]
Table 3: Comparison of various available vaginal birth after cesarean delivery scoring models with the present study model

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The limitations of the current study are small sample size and the single-center study. This can be done at multiple centers for further validity and feasibility of the scoring system.

  Conclusion Top

VBAC scoring system is a potential and a useful predictive tool during antenatal counseling. The use of such a scoring system may enable the obstetricians to predict the chances of successful VBAC in the individual patient and it also evaluates the risks and benefits associated with VBAC, thus improving the outcome of VBAC. Favorable Bishop's score, indication of previous cesarean section, and spontaneous onset of labor are important prognostic factors for a successful VBAC.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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Correspondence Address:
Aruna Nigam,
Department of Obstetrics and Gynaecology, Hamdard Institute of Medical Sciences and Research, Jamia Hamdard, New Delhi
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/injms.injms_77_22


  [Figure 1]

  [Table 1], [Table 2], [Table 3]


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