What is ductus venosus and what does it do?

Oxygen to brain. In the fetus, the ductus venosus shunts approximately half of the blood flow of the umbilical vein directly to the inferior vena cava. Thus, it allows oxygenated blood from the placenta to bypass the liver. In conjunction with the other fetal shunts, the foramen ovale and ductus arteriosus, it plays a critical role in preferentially shunting oxygenated blood to the fetal brain.