The sono-predict study ultrasound prediction of delivery mode: can the first stage prediction model be further improved?

Background: This study aimed to develop a predictive model for intrapartum Caesarean delivery (ICD) in nulliparous women during the active first stage of labour using clinical and ultrasound parameters. Methods: SONO-PREDICT is a prospective longitudinal observational cohort study conducted at Queen Charlotte’s and Chelsea Hospital from 2021 to 2023, including nulliparous women with singleton, cephalic pregnancies at term. Trans-abdominal ultrasound assessed fetal head position, amniotic fluid volume, and fetal Doppler measurements. Transperineal ultrasound measured head-perineum distance (HPD), caput succedaneum, and moulding. Ultrasounds were conducted following digital vaginal examinations. Results: Out of 241 participants, 239 were evaluable, 202 (85%) underwent second assessments. ICD was necessary for 84 (35%). The interval from the onset of active labour to delivery was significantly shorter in participants who delivered vaginally compared to those who required ICD (median duration: 11.8 hours vs. 14.6 hours; p < 0.001). The primary predictors at the first labour assessment were HPD and cervical dilatation (p = 0.003 and p = 0.015, respectively). In the context of repeat assessments, HPD at both assessments and its changes, changes in caput succedaneum, and cervical dilatation at both evaluations and its changes were key variables (p = 0.023, p < 0.001, p = 0.012, p = 0.007, p = 0.015, p < 0.001, and p < 0.001, respectively). Multivariate logistic regression analysis of the single assessment model (n = 239) included HPD and cervical dilatation, yielding an AUC of 0.68. For the repeat assessments model (n = 202), incorporating initial HPD and caput succedaneum and cervical dilatation and its changes, achieved an AUC of 0.89. Conclusion: Single-assessment model demonstrates feasibility and provides reasonable accuracy in predicting intrapartum caesarean delivery. However, incorporating repeat clinical and ultrasound assessments significantly enhances predictive value. HPD, caput succedaneum, and cervical dilatation emerge as the most predictive parameters for ICD.