Fetal blood is returned to the umbilical aeries and the placenta through the

(Reece, 2/e, pp 54, 119-121.) Fetal blood is returned directly to the placenta through the two hypogastric aeries. The distal poions of the hypogastric aeries atrophy and obliterate within 3 to 4 days after bih; remnants are called umbilical ligaments. Fetal oxygenation is aided by the presence of three vascular shunts: the ductus venosus, foramen ovale, and ductus aeriosus. The ductus venosus shunts oxygenated blood from the umbilical vein into the inferior vena cava. The foramen ovale deflects the more oxygenated blood from the right atrium into the left atrium, thereby bypassing pulmonary circulation. Approximately two- thirds of the blood ejected from the right ventricle is shunted pulmonary circulation through the ductus aeriosus.