Final answer:
The other half of the oxygenated blood bypasses the fetal liver through the ductus venosus, directing it towards the heart.
Step-by-step explanation:
In fetal circulation, approximately half of the oxygenated blood entering from the placenta via the umbilical vein bypasses the liver through the vessel called the ductus venosus. This shunt allows the blood to reach the heart more directly, as the fetal liver only requires a small amount of blood. The other major fetal circulatory shunts include the ductus arteriosus and the foramen ovale; however, these are related to bypassing the nonfunctional lungs rather than the liver.
A shunt called the ductus venosus is necessary for healthy fetal circulation because it permits oxygenated blood in the umbilical vein to avoid the liver. The placenta oxygenates the blood, which subsequently passes through the ductus venosus and the inferior vena cava to reach the right atrium by umbilical veins.