Factors associated with the outcome of TOLAC after one previous caesarean section: a retrospective cohort study

Abstract

The factors associated with the outcome of trial of labour after one previous Caesarean Section; a retrospective cohort study. A retrospective observational study was performed on all eligible consecutive singleton pregnancies planned for trial of labour after one previous Caesarean Section (TOLAC) over a period of 18 months to study the success rate of vaginal birth after Caesarean Section (VBAC) and to find out the factors associated with successful and failed TOLAC. All of the data were entered in electronic format and the data was analysed in detail. Of the 1324 women studied, the VBAC rate was 65.3% and the incidence of scar rupture was 0.5%. The composite adverse maternal (postpartum haemorrhage and intensive care admission) and foetal outcome (still birth, 5–minute APGAR <7 and NICU admission) was more in the failed TOLAC group. Various demographic, clinical and obstetric factors were studied in detail between the successful and failed TOLAC groups. The favourable Bishop Score (>4) was independently associated with successful TOLAC (OR 4.3; 95% CI 3.3–5.6 p < .001). Maternal age of >30 years, (OR 0.57; 95% CI 0.41–0.79; p = .001), labour induction (OR 0.43; 95% CI 0.33–0.56; p < .001) and estimated foetal weight of >3500 g (0.31; 95% CI 0.14–0.6; p = .002) were the factors independently associated with failed TOLAC. Previous indication for a Caesarean Section and previous vaginal delivery were not found to be independently associated with the outcome of TOLAC. The predictive models for TOLAC need to be used cautiously and the risk assessment should be done on an individual basis. IMPACT STATEMENT What is already known on this subject? TOLAC is a reasonable strategy in Obstetrics especially after one Caesarean Section to minimise the morbidity associated with rising Caesarean Section. However, the maternal and foetal morbidity are more following unsuccessful TOLAC. The factors which predict the outcome of TOLAC are multifactorial which include maternal demographic factors, previous obstetric factors like indication for Caesarean Section, intraoperative complications, inter-pregnancy interval, current obstetric factors such as gestational age, Bishop Score before delivery, labour factors and foetal factors, e.g. sex and foetal size. What do the results of this study add? We tried to include all the possible factors which probably influence TOLAC and found only Bishop Score, maternal age, foetal size and labour induction were the factors independently associated with the outcome of TOLAC. A Bishop Score of >4 admission was the greatest predictor of successful TOLAC (OR 4.3). Similarly, labour induction and foetal size of >3.5 kg were associated with 60% and 70% less chance of VBAC, respectively. What are the implications of these findings for clinical practice and/or further research? The factors found to be associated with successful and failed TOLAC may be utilised to develop a predictive model. More so, prospective studies are needed to test such predictive models.