Fetal circulation — the circulatory system of a fetus — enables gas and nutrient exchange between the developing fetus and the mother through the placenta. Two umbilical arteries transport blood to the placenta for oxygenation, nutrient enrichment, and waste removal. This enriched blood returns to the fetus via the umbilical vein, which splits into the hepatic portal vein and the ductus venosus. The hepatic portal vein feeds the liver, while the ductus venosus joins the inferior vena cava, where this oxygenated blood mixes with deoxygenated blood from the lower half of the fetal body. Simultaneously, the superior vena cava drains the upper body. Together, these vessels feed into the right atrium. The foramen ovale directs blood from the right atrium to the left atrium, bypassing the fetal lungs. After birth, this opening closes, and blood from the right atrium gets redirected to the lungs for oxygenation. Some blood from the right ventricle enters the pulmonary trunk but gets redirected through the ductus arteriosus to the aorta that feeds the systemic circulation.