Clinical studies linking fetal velocimetry, blood flow and placental transport in pregnancies complicated by intrauterine growth retardation (IUGR).

Our research has focused on two aspects of IUGR pregnancies: first, the changes in the fetal circulation which progress to fetal circulatory failure, and second, to reduced placental transport for amino acid and carbohydrate. There are sequential changes in fetal velocimetry for 8 different velocimetric indices. Measurements of blood flows in the fetal ductus venosus and in the umbilical vein have identified a subset of IUGR fetuses with significantly reduced umbilical blood flow, increased ductal shunt and reduced hepatic flow. Studies of placental amino acid transport in vivo have shown differences between normal and IUGR pregnancies which can be related to the velocimetry data. Clinical severity in FGR pregnancies can be related to 2 different sets of metabolic data. One is that of the glucose gradients across the placenta and another is the fetal/maternal enrichment ratios for amino acids. The implication and extension of these studies will be discussed.