Objective:To explore the method of ultrasonography for detecting the fetal umbilical vein diameter, blood flow volume and normalized volume blood flow and establish normal reference ranges with umbilical vein diameter, blood flow volume and normalized blood flow and Z-scores for umbilical vein diameter and blood volume flow.Methods:This was a prospective study on 907 normal fetuses in the Second Xiangya Hospital, Central South University and Women and Children Healthcare Hospital of Zhuzhou from March 2019 to December 2020. The umbilical vein diameter (Duv), umbilical vein blood flow volume (Quv) and normalized volume blood flow (nQ = Quv/estimated fetal weight) of the free loop of umbilical vein (FUV) and fetal intra-abdominal umbilical vein (IUV) were collected. And the mean values and 90% confidence intervals of Duv, Quv and nQ in two segments of umbilical veins at different gestational ages were calculated. Regression analysis of Duv, Quv and nQ were performed with gestational age (GA), and the parameters of umbilical vein in different segments were compared. Finally, with gestational age (GA) as the independent variable, Z-scores of the Duv and Quv were built.Results:The mean values and 90% confidence intervals of Duv, Quv, and nQ in 858 (94.6%) normal fetal umbilical veins were successfully obtained. The Duv, Quv of the FUV and IUV increased as pregnancy progressed. The Quadratic curve of Duv and Linear curve of Quv were of the highest fitnesses, respectively( r=0.951, 0.941, 0.986, 0.982; all P<0.001). While nQ increased with GA followed by a decreased trend, and the Quadratic curve was the highest fitting curve of nQ( r=0.610, 0.611; all P<0.001). Duv-FUV was greater than Duv-IUV( P<0.001), nQ-FUV was bigger than Quv-IUV( P=0.001), and he difference was not statistically significant between Quv-FUV and Quv-IUV( P=0.133). Z-scores models of Duv and Quv were successfully established, and all Z-scores were Gaussian distribution. Conclusions:The normal ranges and Z-scores of umbilical vein parameters are useful to improve the evaluation of placental circulation and provide a strong basis for the monitoring of fetus-related diseases and the evaluation of pregnancy prognosis. The choice of FUV or IUV umbilical vein to evaluate placental circulation may depend on the actual situation in clinical application.