Reference ranges of fetal ductus venous and umbilical vein flow during second and third trimester

Objective To establish reference ranges with gestation for blood flow of fetal ductus venosus(DV) and umbilical vein(UV) and determine the fraction of umbilical blood shunted through the DV in the human fetus. Methods Color Doppler flow ultrasound was used to examine 138 normal singleton pregnancies at 16～41 weeks gestation. Flow velocity waveforms were recorded from the DV and UV. Peak velocity during ventricular systole was measured at DV inlet. DV and UV blood flow were calculated. Results The blood flow increased as pregnancy progressed(P 0.01 ), while blood flow per kilogram of estimated body weight calculated for DV decreased as pregnancy progressed(P 0.01 ). The blood velocity, the diameter and the blood flow in UV increased as pregnancy progressed(P 0.05 , P 0.01 , P 0.01 ). Blood flow per kilogram of estimated body weight calculated for UV decreased pregnancy progressed(P 0.01 ). Qdv/Quv ratio decreased as pregnancy progressed(P 0.01 ). The average fraction shunted through the DV was 43 during the second and third trimester. Conclusions The blood flow from UV shunted through the DV decreases as pregnancy progressed during the second and third trimester. DV plays less role in shunting high oxygen blood flow to heart and brain.