Objective:To investigate the predictive value of cerebroplacental ratio (CPR) for adverse perinatal outcomes of induction of labor in prolonged pregnancy.Methods:This retrospective study recruited 315 singleton pregnant women who had induced labor due to prolonged pregnancy (≥41 gestational weeks) in the First Affiliated Hospital of Chongqing Medical University from January 1, 2019 to April 30, 2020. Based on the occurrence of adverse perinatal outcomes (emergency delivery due to persistent abnormal fetal heart rate monitoring, umbilical artery blood pH at birth <7.2, 5 min Apgar scores<7, transferring to neonatal intensive care unit after birth, chorioamnionitis and vaginal delivery converted to cesarean section), they were divided into two groups: case group ( n=76) and normal group ( n=239). Clinical features and umbilical artery blood flow, middle cerebral artery (MCA) flow and CPR measured in the last ultrasound scan before induction were compared between the two groups using student's t-test, Mann-Whitney U test and Chi-square test. Receiver operating characteristic (ROC) curve was used to analyze the predictive values of umbilical artery blood flow, MCA flow and CPR for the adverse perinatal outcomes. Multivariate logistic regression analysis was used to screen the meaningful predictors. Results:Compared with the normal group, the umbilical artery pulsatility index (PI) (0.9±0.1 vs 0.8±0.1, t=-5.458, P<0.001) and the percentage of abnormal CPR (<1.0) increased significantly [21.1%(16/76) vs 6.3%(15/239), χ2=14.190, P<0.001] in the case group, while the MCA-PI and CPR decreased significantly (1.1±0.2 vs 1.3±0.3, t=5.658, P<0.001; 1.2±0.3 vs 1.6±0.5, t=8.940, P<0.001). The areas under the ROC curves of umbilical artery PI, MCA-PI and CPR for predicting adverse perinatal outcomes were 0.71, 0.71 and 0.77, respectively. CPR had the highest sensitivity (0.74) compared with umbilical artery PI (0.68) and MCA-PI (0.71), but the specificity of them were similar (0.67, 0.66 and 0.66). Multivariate logistic regression analysis showed that only CPR was the independent risk factor for adverse perinatal outcomes ( OR=0.028, 95% CI: 0.010-0.080, P<0.001). Conclusions:As an indicator for early prediction of adverse perinatal outcomes of induction of labor in prolonged pregnancy, CPR was more sensitive but less specific.