Blood flow through the fetus is actually more complicated than after the baby is born (normal heart). That’s because in the mother, the placenta is doing the work that the baby’s lungs will do after birth. The placenta also functions as the gastrointestinal tract, liver and kidneys for the growing fetus. Oxygenated, nutrient-rich blood from the placenta is carried to the fetus by the umbilical vein. This blood enters through the inferior vena cava (the large vein that carries blood from the lowe