Umbilical cord carries oxygenated, nutrient-rich blood to the fetus, and two arteries that carry deoxygenated, nutrient-depleted blood away. Occasionally, only two vessels (one vein and one artery) are present in the umbilical cord. This is sometimes related to fetal abnormalities, but it may also occur without accompanying problems. It is unusual for a vein to carry oxygenated blood and for arteries to carry deoxygenated blood (the only other examples being the pulmonary veins and arteries, connecting the lungs to the heart). However, this naming convention reflects the fact that the umbilical vein carries blood towards the fetus's heart, while the umbilical arteries
Umbilical vein Umbilical vein The umbilical vein is a vein present during fetal development that carries oxygenated blood from the placenta into the growing fetus. The umbilical vein provides convenient access to the central circulation of a neonate for restoration of blood volume and for administration of glucose and drugs. The blood pressure inside the umbilical vein is approximately 20 mmHg. The unpaired umbilical vein carries oxygen and nutrient rich blood derived from fetal-maternal blood exchange at the chorionic villi. More than two-thirds of fetal hepatic circulation is via the main portal vein, while the remainder is shunted from the left portal