A 2-day-old infant boy has been diagnosed with an atrial septal defect due to a persistent patent foramen ovale. When explaining the diagnosis to the mother, the nurse includes in the discussion the function of the foramen ovale. In fetal circulation, the foramen ovale allows a portion of the blood to bypass the:

The foramen ovale permits a percentage of the blood to shunt from the right atrium to the left atrium. The blood then goes to the left ventricle, permitting systemic fetal circulation with blood containing a higher O2 saturation. As the blood shunts from the right atrium to the left atrium, the pulmonary system is bypassed. The fetus receives O2 from the maternal circulation, thereby permitting the partial bypass of the pulmonary system. The foramen ovale is located in the atrial septum of the heart and does not affect the liver. The superior vena cava returns blood to the heart, bringing blood to the location of the foramen ovale.