In fetal circulation, which vessel carries oxygenated blood back to the fetal heart?

• A. Pulmonary artery
• B. Umbilical artery
• C. Ductus venosus
• D. Umbilical vein

Answer: (D)

Oxygenated blood returns to the fetus via the umbilical vein. This vessel carries blood rich in oxygen from the placenta into the fetal circulation. As it enters the fetus, much of that blood is routed through the ductus venosus directly into the inferior vena cava, delivering highly oxygenated blood toward the heart and onward to the systemic circulation. The other vessels have different roles: the pulmonary artery carries blood away from the heart to the lungs (which are not used for gas exchange in the fetus), the umbilical artery carries deoxygenated blood from the fetus to the placenta, and the ductus venosus is a shunt that helps move a portion of umbilical venous blood to the heart by bypassing the liver.