Abstract: Objective  To study placental blood flow status, fetal middle cerebral artery (MCA) blood flow and cerebroplacental ratio (CPR) in predicting late-onset fetal growth restriction. 
Methods  A total of 120 women with limited fetal delivery in our hospital were selected as the case group, while 60 women with normal fetal delivery during the same period were selected as the control group. The placental blood flow status, CPR and MCA blood flow parameters were detected by three-dimensional Doppler ultrasound. The clinical baseline data were analyzed by univariate analysis. The influencing factors of fetal growth were determined by Logistic regression analysis. Receiver operating characteristics (ROC) curve was used to analyze various indicators and Logistic regression analysis was used to analyze the diagnostic efficacy. 
Results  The parameters of placental blood flow state, including blood flow index (FI), vascularization index (VI) and vascularization-blood flow index (VFI), of the pregnant women in the case group were significantly lower than those of control group. Pulsatility index (PI), resistance index (RI) and CPR were significantly lower in the case group than in the control group, while EDV was significantly higher in the case group than in the control group. CPR was positively correlated with FI, VI, VFI, PI and RI (r=0.185, 0.594, 0.854, 0.696, 0.701, P＜0.05), but negatively correlated with EDV (r=-0.452, P＜0.05). Logistic regression analysis showed that FI, VI, VFI, PI, RI, EDV and CPR were the influencing factors of FGR. 
Conclusion  CPR, placental blood flow status and MCA blood flow parameters are abnormal in pregnant women with FGR. CPR, FI, VI, VFI, PI, RI and EDV parameters alone and Logistic regression analysis can be applied to the prediction and diagnosis of FGR.

Key words: fetal growth restriction, cerebroplacental ratio, middle cerebral artery blood flow