Development and internal validation of a model predicting successful trial of labour among pregnant individuals with previous one caesarean section: A cohort study (DEVI-CS model)

Objective: To develop and internally validate a model predicting successful trial of labour among pregnant women with previous caesarean scar. Design: Cohort study. Setting: Tertiary care and teaching hospital. Participants: All pregnant women with one previous caesarean delivery, presenting with singleton pregnancies in cephalic presentation at a gestation age of 37 weeks or more between 2018 and 2022. Main outcome measures: A stepwise multivariable logistic regression, followed by bootstrapping, was used to develop and validate the model. Success was defined as vaginal birth after caesarean section (VBAC) without complications for the mother and baby. Result: Out of 4515 cases of TOLAC, 39.8 % had a successful trial of labour. Maternal age (OR = 0.950, 95 %CI: 0.927-0.974), previous baby weight (OR = 1.000, 95 %CI: 1.000-1.001), indication of previous caesarean section such as breech presentation (OR = 0.453, 95 %CI: 0.315-0.652), failed induction (OR = 0.346, 95 %CI: 0.267-0.447), BISHOP score (OR = 1.725, 95 %Cl: 1.673-1.774) and induction of labour (OR = 0.587, 95 %CI: 0.466-0.741) were the strongest predictors of successful TOLAC. DEVI-CS model showed good discrimination with an area under the curve (AUC) of 0.928(95 %CI: 0.921-0.936) and good agreement between predicted and observed probabilities. Decision curve analysis showed a net benefit between 5 % and 90 % between the predicted thresholds. Conclusion: The new DEVI-CS prediction model, based on easily captured clinical variables, can quantify the chances of a successful trial of labour after a previous caesarean section. It could aid in shared decision-making regarding the mode of delivery among women with planning the trial of labour after caesarean section.