Blood flow and the degree of shunting through the ductus venosus in the human fetus.

Abstract

Our goal was to determine the degree of shunting through the ductus venosus in the human fetus and its possible association with fetal growth. Blood flow in the umbilical vein and the fetal ductus venosus was measured in 197 low-risk pregnancies in a cross-sectional ultrasonographic study at a gestational age of 18 to 41 weeks. The degree of shunting was compared to birth weight and ponderal index. The average fraction shunted through the ductus venosus was 28% to 32% at 18 to 20 weeks, decreased to 22% at 25 weeks, and reached 18% at 31 weeks (with wide ranges expressed in the 10th and 90th percentiles). Fetuses <10th percentile for birth weight had significantly more shunting (1.4%) than those >90th percentile (95% confidence interval, 0.1%-2.7%; P =.04). In the human fetus a higher proportion of umbilical blood is directed to the liver and less is shunted through the ductus venosus, in comparison with what has previously been shown in animal experiments.