Hepatic artery hemodynamics suggest operation of a buffer response in the human fetus.

After birth, the hepatic artery buffer response helps to maintain liver perfusion. Here, the authors establish a Doppler technique to measure fetal hepatic artery flow velocity and test the hypothesis that the buffer response also operates prenatally. Women with low-risk pregnancies were recruited to a longitudinal study (N = 161). Measurement techniques and reference ranges for hepatic artery velocities and pulsatility index (PI) were established. Ductus venosus peak velocity (V(DVps)) represented the portocaval pressure gradient, and umbilical venous flow (Q(UV)) represented portal flow. Reference ranges were established for the more accessible left hepatic artery branch. Hepatic artery PI was lower in fetuses with V(DVps) <10th centile (P < .05) and in those with Q(UV) <10th centile ( P < .0001). Conversely, hepatic artery PI was higher in those with Q(UV) >90th centile (P < .0001). The authors establish a method for measuring fetal hepatic arterial blood velocity, provide reference ranges, and show that the hepatic artery buffer response operates prenatally.