Umbilical vessels are arteries and veins in the umbilical cord that transfer blood, oxygen and nutrients between the fetus and its mother. Blood-borne waste removed from the fetus also travels out of the fetus through the umbilical vessels. These vessels are attached to the membrane of the placenta, enabling them to absorb nutrition from the placenta through the process of diffusion. Once the placenta is expelled from the mother after birth, the vessels stop working within minutes, but the red and purple arteries and veins can still be seen in the thin membrane surrounding the umbilical cord. After expulsion, the vessels constrict to prevent massive blood loss from the baby.
The developing fetal circulatory system works in conjunction with the umbilical vessels until the baby is fully able to handle blood circulation independently. Once a woman becomes pregnant, the umbilical vessels begin forming within the first three weeks. By the fifth week, the vessels are fully developed and surrounded by a budding umbilical cord. The blood they carry is more oxygen-rich than typical human blood. Medical books suggest the vessels carry blood with as much as 50 percent more oxygen than the gestating mother’s blood.
Typically, only one umbilical vein carries this highly-concentrated oxygen and other nutrition from the placenta to the growing baby, while two umbilical arteries carry the blood back to the placenta where it can become reoxygenated. Before these fetal vessels are formed, the baby must remain attached directly to the developing placenta to survive. A small stalk on the placenta is the place where the mesh of fetal blood vessels begins to develop and eventually become enveloped by the umbilical cord. Since the vessels are so essential to the baby’s survival, the cord forms during the same developmental phase as the umbilical vessels for the sole purpose of protecting these fragile, nutritious pathways. If circulation through the fetal blood vessels is hampered in any way, developmental problems and permanent baby defects can occur.
The umbilical vessels are cushioned by a viscous environment known as Wharton’s Jelly. This jelly protects the vessels against breakage as the umbilical cord undergoes twisting and turning as the fetus develops. Occasionally, problems can occur during the formation of umbilical blood vessels. For example, sometimes one artery forms instead of two; this happens in less than 1 percent of babies and is frequently linked to pregnant women who are smokers, according to medical reports. Hernias at the site where the umbilical cord attaches can also occur, affecting the function of vessels.