Objective: To develop and validate a predictive model assessing the risk of cesarean delivery in primiparous women based on the findings of magnetic resonance imaging (MRI) studies. Design: Observational study Setting: University teaching hospital. Population: 168 primiparous women with clinical findings suggestive of cephalopelvic disproportion. Methods: All women underwent MRI measurements prior to the onset of labor. A nomogram model to predict the risk of cesarean delivery was proposed based on the MRI data. The discrimination of the model was calculated by the area under the receiver operating characteristic curve (AUC) and calibration was assessed by calibration plots. The decision curve analysis was applied to evaluate the net clinical benefit. Main Outcome Measures: Cesarean delivery. Results: A total of 88 (58.7%) women achieved vaginal delivery, and 62 (41.3%) required cesarean section caused by obstructed labor. In multivariable modeling, the maternal body mass index before delivery, induction of labor, bilateral femoral head distance, obstetric conjugate, fetal head circumference and fetal abdominal circumference were significantly associated with the likelihood of cesarean delivery. The discrimination calculated as the AUC was 0.845 (95% CI: 0.783-0.908; P < 0.001). The sensitivity and specificity of the nomogram model were 0.918 and 0.629, respectively. The model demonstrated satisfactory calibration. Moreover, the decision curve analysis proved the superior net benefit of the model compared with each factor included. Conclusion: Our study provides a nomogram model that can accurately identify primiparous women at risk of cesarean delivery caused by cephalopelvic disproportion based on the MRI measurements.

Objective: To develop the prediction models for identifying fetal occiput rotation and vaginal delivery based on intrapartum sonographic findings. Design: Prospective observational study. Setting: Hangzhou, China. Population: Nulliparous women with a singleton cephalic presentation at term. Methods: Serial intrapartum ultrasonography were performed in the latent phase (T1) and every three hours after that (T2, T3 and T4). The managing clinicians performed paired digital vaginal examinations to assess labor progress. Main Outcome Measures: Delivery mode and successful internal fetal head rotation to the occiput anterior (OA) position. Results: 614 women were included, of whom 524 underwent vaginal delivery, and 90 required cesarean section. The percentage of women with fetuses in non-occiput anterior position at the latent phase was 53.9% (331 cases), as 257 women underwent spontaneous rotation to OA position before delivery, 74 were with persistent occiput posterior or transverse position. We developed a model on the basis of the maternal height and middle angel to predict the spontaneous fetal occiput rotation, with the area under the receiver operating characteristic curve (AUC) was 0.667 (95%CI 0.583-0.751). Moreover, a prediction model based on the maternal height and angle of progression to evaluate whether women underwent vaginal delivery was also developed, of which the AUC was 0.738(95% CI: 0.763-0.793). Both models showed satisfactory calibration. Conclusion: Simple models based on maternal characteristics and intrapartum ultrasound findings might provide useful information for predicting vaginal delivery and internal fetal occiput rotation.