Objective To investigate the incidence rates of different fetal variations of inferior vena cava, and to compare the diameters and peak velocity of blood in the inferior vena cava between the normal and changed inferior vena cava. Methods Prenatal ultrasound data of 37 448 fetuses were retrospectively analyzed. We screened out the cases with variation of inferior vena cava,and calculated related incidence. Then the diameters and S-wave peak velocity of the inferior vena cava in fetuses of the two groups were measured and compared. Results We found 54 (1.44‰) cases of left inferior vena cava and 14 (0.37‰) cases of double inferior vena cava. The diameter of normal fetal inferior vena cava was (2.71±0.42) mm and the peak velocity was (36.25±6.30) cm/s, the diameter of the left inferior vena cava was (2.70±0.45) mm and the peak velocity was (36.55±7.53) cm/s, both showing no significant difference when compared with the normal group (t=6.78, P>0.05; t=3.56, P>0.05). The diameter of double inferior vena cava was (2.72±0.50) mm and the peak velocity was (36.18±7.49) cm/s, showing no significant difference when compared with the normal group (t=10.43, P>0.05; t=7.01, P>0.05). Conclusion The incidence rates of left inferior vena cava and double inferior vena cava in fetuses have been found to be 1.44‰ and 0.37‰, respectively, and they have similar diameters and velocity with normal inferior vena cava.