Umbilical blood flow during pregnancy: evidence for decreasing placental perfusion

Due to the growth of the umbilical vein, UmbBF increases over the last weeks of gestation. The ratio UmbBF/FW is reduced in FT. Despite a constant O2 content, the continuous weight-related decrease in UmbBF results in a reduction of the fetal O2 transport capacity per unit that may contribute to an adverse intrauterine environment at the end of gestation, especially in postterm pregnancies.