The relationship between Doppler indices from inferior vena cava and hepatic veins in normal human fetuses.

This study was conducted to determine the gestational age-related reference range of the preload index [peak velocity during atrial contraction (A)/peak velocity during ventricular systole (S)] for the inferior vena cava (IVC), the right hepatic vein, the middle hepatic vein and the left hepatic vein. The slope and the intercept of the regression line for each preload index were compared among the 4 veins using analysis of covariance. Doppler measurements were obtained for the 4 veins of 316 normal fetuses at 22-40 weeks of gestation. A and S values were measured from the recorded flow velocity waveform of each vein and the A/S ratio was calculated as the preload index. The regression lines for the preload index of the 4 veins decreased gradually throughout gestation. Analysis of covariance revealed no significant differences in the slopes of the regression lines for the 4 veins. However, the intercepts of the regression lines for all hepatic veins were significantly higher than that of the regression line for the IVC (P<0.0001), with the difference ranging from 0.024 to 0.033. There were no significant differences among the intercepts of the regression lines for different hepatic veins. We concluded that the relationship between the preload index and the duration of gestation was statistically similar for all hepatic veins, and strongly resembled that for the IVC.