Vaginal birth after cesarean section and its associated factors in Ethiopia: a systematic review and meta-analysis

The prevalence of cesarean sections is rising rapidly and is becoming a global issue. Vaginal birth after a cesarean section is one of the safest strategies that can be used to decrease the cesarean section rate. Different fragmented primary studies were done on the success rate of vaginal birth after cesarean section and its associated factors in Ethiopia. However, the findings were controversial and inconclusive. Therefore, this meta-analysis was intended to estimate the pooled success rate of vaginal birth after cesarean section and its associated factors in Ethiopia. Pertinent studies were searched in PubMed, Google Scholar, ScienceDirect, direct open-access journals, and Ethiopian universities' institutional repositories. The data were analyzed using Stata 17. The Newcastle–Ottawa quality assessment tool was used to assess the quality of the studies. I squared statistics and Egger’s regression tests were used to assess heterogeneity and publication bias, respectively. A random effects model was selected to estimate the pooled success rate of vaginal birth after cesarean section and its associated factors. The PROSPERO registration number for this review is CRD42023413715. A total of 10 studies were included. The pooled success rate of vaginal birth after a cesarean section was found to be 48.42%. Age less than 30 years (pooled odds ratio (OR) 3.75, 95% CI 1.92, 7.33), previous history of vaginal birth (OR 3.65, 95% CI 2.64, 504), ruptured amniotic membrane at admission (OR 2.87, 95% CI 1.94, 4.26), 4 cm or more cervical dilatation at admission (OR 4, 95% CI 2.33, 6.8), a low station at admission (OR 5.07, 95% CI 2.08, 12.34), and no history of stillbirth (OR 4.93, 95% CI 1.82, 13.36) were significantly associated with successful vaginal birth after cesarean section. In conclusion, the pooled success rate of vaginal birth after a cesarean section was low in Ethiopia. Therefore, the Ministry of Health should consider those identified factors and revise the management guidelines and eligibility criteria for a trial of labor after a cesarean section.

(Preferred Reporting Items for Systematic Reviews and Meta-analyses) guideline 26 (Table S1). The protocol was registered in PROSPERO. The PROSPERO registration number for this review is CRD42023413715. We used PubMed, Google Scholar, ScienceDirect, and direct open-access journal (DOAJ) databases to find relevant studies. Initially, studies were exhaustively searched by using the full title ("Vaginal birth after cesarean section and its associated factors in Ethiopia") and keywords ("success rate," "successful," "vaginal birth after a cesarean section", "vaginal delivery after the cesarean section", "trial of labor after the cesarean section", "determinants", "associated factors", "predictors", "Ethiopia"). These keywords were connected using the Boolean operators ("OR" and/or "AND"). Besides this, reference lists of all included studies were assessed to find missed studies. Moreover, unpublished studies were searched in Ethiopian universities' institutional repositories, mainly at the University of Gondar, Jimma, Addis Ababa, and Haramaya. The search details for PubMed were as follows: ( (Table S2).
Eligibility criteria. The authors followed CoCoPop approaches (condition, context, and population) to establish search strategies and identify eligible studies.
Inclusion criteria: This systematic review and meta-analysis included articles that fulfilled the following criteria: • Condition (Co): We included studies that examined at least one or more of the following key outcomes: (1) success rate of vaginal birth after cesarean section; (2)  Outcome measurement. This meta-analysis study has two outcomes, namely, the success rate of vaginal birth after cesarean section and its associated factors.
Station: It refers to the relationship of the fetal head's lowermost portion in the pelvic canal with the ischial spines or indicates the degree of engagement of the presenting part. The station above the ischial spine was categorized as high (0), and the station below the ischial spine was categorized as low (> 0) in the pelvic examination 24 .
Heterogeneity: We used the following cut points to define the level of heterogeneity: When I-squared (I 2 ) is zero, there is no heterogeneity; if the value is 25%, there is mild heterogeneity; if the value is 50%, there is The pooled success rate of vaginal birth after cesarean section in Ethiopia. Five primary studies were included to determine the pooled success rate of vaginal birth after a cesarean section 24,25,34,36,38 . The pooled success rate of vaginal birth after a cesarean section was 48.42 with a 95% CI of 35.72 to 61.1. A marked type of heterogeneity was detected across the studies (I 2 = 95.7%). The highest rate of successful vaginal birth after a cesarean section was reported by Misgan et al. 25 , while the lowest success rate of VBAC was reported by Derebe et al. 24 (Fig. 2). Subgroup analysis. Subgroup analysis was done to identify the source of heterogeneity and minimize the random variations between the point estimates of primary studies and pooled success rate of VBAC by using sample size, publication status, and study period. However, heterogeneity was still observed between the studies. The overall success rate of VBAC was found to be 54.22% in published studies, 55.57% in studies with a sample size of less than 300, and 48.45% in studies conducted after 2018 (Table 2). Sensitivity analysis. Sensitivity analysis was done to check the influences of individual studies on the overall success rate of VBAC. There was no significant influence of individual studies on the pooled success rate of VBAC. When Derebe et al. and Misgan et al. were excluded from the analysis, the pooled success rate of VBAC was found to be high and low, with success rates of 51.82% and 42.67%, respectively (Table 3).
Publication bias. Publication biases were assessed objectively by using Egger's regression test, and the results indicated that there was no publication bias or small study effect between the studies (p-value = 0.683).
Factors associated with successful vaginal delivery after cesarean section. A total of nine studies reported one or more associated factors for successful VBAC. The most common factors reported by the majority of studies were a history of vaginal birth, a ruptured amniotic membrane at admission, and a cervical dilatation of four or more centimeters at admission ( Table 4).
The relationship between cervical dilation at admission and vaginal birth after cesarean section: The effect of cervical dilation at admission on successful vaginal birth after a cesarean section was evaluated using six studies 24,25,31,[34][35][36] . In this study, cervical dilation of more than or equal to 4 cm at admission was found to be significantly associated with a successful vaginal birth after a cesarean section. Those mothers with cervical dilation ≥ 4 cm at admission were four times more likely to have a successful VBAC (pooled odds ratio 4, 95% CI 2.33, 6.8) (Fig. 3).
The association between ruptured amniotic membrane at admission and VBAC: Three primary studies were used to determine the relationship between ruptured membranes and successful VBAC 24 (Fig. 4).
The association between having a low station at admission and successful VBAC: The association between having a low station at admission (station ≥ 0) and successful VBAC was examined using three studies 24    www.nature.com/scientificreports/ who had a low station at admission were 5.11 times more likely to have a successful VBAC than mothers with a high station (pooled odds ratio 5.07, 95% CI 2.08, 12.34) (Fig. 5).
The association between previous history of vaginal delivery and successful VBAC: Five studies were used to investigate the relationship between previous vaginal delivery history and successful VBAC 24,[32][33][34][35] . This study discovered that a previous history of vaginal birth was significantly associated with a successful VBAC. Those mothers with a previous history of vaginal delivery were 3.65 times more likely to have a successful vaginal birth after a cesarean section (pooled odds ratio 3.65, 95% CI 2.64, 504) (Fig. 6).
The association between no history of stillbirth and successful VBAC: Three primary studies were used to examine the relationship between no history of stillbirth and successful VBAC 31,32,37 . The result showed that mothers     Note: Weights are from random effects analysis www.nature.com/scientificreports/ with no history of stillbirth were 4.93 times more likely to have a successful VBAC than mothers with a history of stillbirth (pooled odds ratio 4.93, 95% CI 1.82, 13.36) (Fig. 7).
The association between maternal age and successful VBAC: Finally, we used two studies to examine the relationship between maternal age below 30 years and successful VBAC 24,35 . This study found that maternal age under 30 years was significantly associated with successful VBAC. Those mothers whose age was less than 30 years were 3.75 times more likely to have a successful VBAC as compared to those with older age (pooled odds ratio 3.75, 95% CI 1.92, 7.33) (Fig. 8).

Discussion
This meta-analysis assessed the pooled success rate of VBAC and its associated factors in Ethiopia. To the best of our knowledge, this research is the first of its type in Ethiopia to examine the overall success rate of VBAC and the contributing factors.
The pooled success rate of VBAC was found to be 48.42% with a 95% CI of 35.72 to 61.1. This finding was lower than a study finding in Australia (64.4%) 39 , the UK (63.4%) 20 , and China (84%) 22 . This finding was also lower than a finding of a meta-analysis study in developed countries 40 . The variation in the success rate of VBAC across countries could be due to differences in hospital settings or eligibility criteria for a trial of labor after a cesarean section. Furthermore, the higher success rate of VBAC in the previous studies might be due to the availability of advanced labor monitoring machines, which might decrease the unnecessary repeated CS. In addition, the discrepancies might be due to the variations in the management modalities for labor abnormalities among those mothers who had TOLAC. In our country, CS is the only treatment option for prolonged labor secondary to poor uterine contractions among those mothers who had a TOLAC.
The finding of this study was also lower than the finding of a meta-analysis study in Sub-Saharan African countries, which has a 69% success rate of VBAC 41  www.nature.com/scientificreports/ disparities in sample size, where the previous study used several primary studies and a large sample size as compared to our study. In addition, discrepancies in the threshold level for TOLAC, intrapartum fetal monitoring, and quality of health services between the countries might contribute to this difference. The finding of this study revealed that having a ruptured amniotic membrane at admission was significantly associated with successful VBAC. This finding was supported by a study finding in China 22 . This could be explained by the release of natural prostaglandins during the rupture of the amniotic membrane. Prostaglandin facilitates the progress of labor and decreases the chance of labor abnormalities, mainly poor uterine contractions 42 .
This study also found a strong association between previous history of vaginal delivery and successful VBAC. This finding is in agreement with a study finding in China 22 , Turkey 23 , and Thailand 14 . This finding is also in agreement with a meta-analysis study, which revealed that the history of previous vaginal deliveries is one of the most important factors for the success of VBAC 40 . The possible reason could be due to good psychological readiness and awareness of the advantage of vaginal delivery in those mothers with a history of vaginal delivery.
This study also found a strong association between a cervical dilatation of four centimeters or more at admission and a successful VBAC. Evidence from Pakistan 13 and Nigeria 6 supports the current finding. This might be because obstetric care providers usually encourage TOLAC when cervical dilatation is more than or equal to 4 cm. Furthermore, those mothers who are in the active phase of labor might have better progress of labor that results in successful VBAC as compared to the latent first stage of labor.
Maternal age below 30 years was also significantly associated with successful VBAC. Evidence from the meta-analysis study supports the present finding and revealed that younger women, especially those 35 years old, are more likely to have a successful and safe VBAC 40 . Another study also reported that maternal age of above 30 years was independently associated with Failed TOLAC 43 . This may be because older mothers are less likely to attempt TOLAC due to a fear of urine rupture.
Furthermore, we found a strong association between a low station at admission and a successful VBAC. This finding was supported by a previous study that reported that women who had a station lower than − 1 were significantly associated with successful VBAC 44,45 .
Lastly, no history of stillbirth was significantly associated with a successful VBAC. Evidence revealed that a history of fetal complications or adverse birth outcomes in the previous pregnancy increased the cesarean delivery rate 46 . Previous history of stillbirth during labor could influence women's preferences on the mode of delivery and the obstetric care provider's decision to halt or continue a vaginal birth in women with a history of cesarean section 1 .
This study has some limitations. The lack of studies from some regions might affect the generalizability of this study. Furthermore, the presence of heterogeneity across the studies might affect the pooled success rate of VBAC.

Conclusion
The overall success rate of VBAC was low in Ethiopia. A successful VBAC was significantly associated with a history of vaginal birth, a ruptured amniotic membrane at admission, a low station at admission, age less than 30 years, cervical dilatation of four or more centimeters at admission, and no history of stillbirth. Therefore, the Ministry of Health should consider those identified factors and revise the management guidelines and eligibility criteria for TOLAC. Moreover, obstetric care providers should prevent repeated CS by providing appropriate antenatal counseling regarding influencing factors for VBAC and the chance of achieving a successful VBAC.