Intrapartum Transperineal Ultrasound Parameters as Predictive Biomarkers for Delivery Mode and Labor Duration in Primiparas: A Prospective Cohort Study

Objective: This study evaluates the utility of intrapartum transperineal ultrasound parameters—angle of progression (AOP), head-perineum distance (HPD), and midline angle (MLA)—as predictors of delivery mode and labor duration in primiparas. Methods: A prospective cohort of 144 primiparas (gestational age: 38–40 weeks) undergoing trial of labor was stratified into vaginal delivery (n = 108) and cesarean section (n = 36) groups. Transperineal ultrasound assessed fetal orientation, cervical metrics, AOP, HPD, and MLA during the first stage of labor. Statistical analyses included receiver operating characteristic (ROC) curves for delivery mode prediction, linear regression and Pearson correlations for labor duration. Results: Vaginal deliveries exhibited significantly higher AOP (136.59° ± 10.24° vs 116.24° ± 6.53°), lower HPD (21.06 ± 3.21 cm vs 24.39 ± 2.14 cm), lower and MLA (11.31° ± 1.33° vs 15.26° ± 2.45°) compared to cesarean deliveries. ROC analysis demonstrated strong predictive efficacy of delivery mode for combined parameters (AUC = 0.884). AOP and MLA negatively correlated with labor duration (r = −0.737, −0.761; p < 0.001), while HPD showed a positive correlation (r = 0.644, p < 0.001). Conclusion: AOP, HPD, and MLA are robust biomarkers for predicting delivery mode and labor progression. Integrating these parameters into clinical practice may enhance decision-making, reduce unnecessary interventions, and improve maternal-neonatal outcomes.