To explore the feasibility of prenatal ultrasound in predicting delivery mode of full-term primipara.

The study prospectively enrolled primiparas with gestational age ≥37 weeks, singleton, cephalic and no contraindications to vaginal delivery who underwent routine prenatal examination in the Third Affiliated Hospital of Sun Yat-sen University from September 2020 to February 2021.In addition to routine fetal ultrasound examination, the transperineal ultrasound examination was performed to assess the angle of progression (AOP), head perineum distance (HPD), the angle of pubic arch and the anteroposterior diameter, left and right diameter, area and perimeter of levator ani hiatus of pregnant women in different states were measured; Cervical length (CL) was examined by transvaginal ultrasound. The delivery mode was tracked, and the indicators related to natural delivery were screened out. Receiver operating characteristic (ROC) curve was used to evaluate the effectiveness of relevant indicators in predicting natural delivery.

A total of 142 cases were included in this study, including 112 cases of natural delivery and 30 cases of manual intervention delivery. There were no significant differences in age, gestational weeks, biparietal diameter, head circumference, body mass index (BMI) and neonatal weight between the natural delivery group and the manual intervention delivery group (all P>0.05). Multivariate regression analysis showed that AOP was associated with natural delivery(OR=1.048, P=0.008). ROC curve analysis showed that the area under the curve was 0.648 with AOP 96.92° as the node, and the specificity and positive predictive values were 83.33% and 0.909 1 respectively.

It is feasible to predict the mode of delivery by prenatal ultrasound in full-term primiparas. AOP is related to the mode of delivery, which can provide more reference information for clinical practice.

Ultrasonography, prenatal; Pelvic floor; Prediction; Mode of delivery; Angle of progression