What Happens to the Umbilical Cord during Pregnancy?

During pregnancy, the umbilical cord connects the fetus to the placenta and is comprised of two arteries and one vein. The arteries carry blood to the placenta while the vein takes it to the growing fetus. Cord lengths can vary quite a lot, but the average length is 60 cm (23.6 in), and most cords exhibit a twisting, helical shape. When the umbilical cord grows normally, a healthy baby is delivered with the cord intact. Since it is no longer needed, the cord is cut after birth. The spot where the umbilical cord used to be turns into the belly button. There are cases where the umbilical cord during pregnancy has defects, indicating other congenital problems in the baby or leading to difficult deliveries or even fetal mortality in some situations.

An umbilical cord during pregnancy that grows too long can be risky for the baby, as long cords are more prone to becoming knotted. True knots can restrict the flow of blood to the fetus and lead to significant health problems. The cord might also loop around the fetus in a condition called "nuchal cord. Fetuses wrapped in an umbilical cord in this manner tend to exhibit irregular heartbeats during delivery. Both true knots and nuchal cord can be detected in utero. Both are caused by the fetus’s movement, usually in the early stages of pregnancy when it has more room to move. It is also important to note that the umbilical cord during pregnancy frequently twists or creates false knots without harming the fetus at all.

Some umbilical cords will only have one artery instead of two. While a rare condition, single umbilical artery tends to lead to fetal demise. Infants born with an umbilical cord that has only one artery have higher rates of cardiovascular problems, gastrointestinal defects, kidney issues and other anomalies. Single umbilical artery can be detected during pregnancy and, if discovered, will likely lead to a number of other tests to check for any abnormalities in the fetus’s development.

Other conditions such as hematomas, cysts, or cord prolapse are quite rare, occurring in less than 1% of all births. For women carrying multiples, the risks associated with the umbilical cord during pregnancy do increase somewhat, especially if the fetuses are sharing the same amniotic fluid. With less room for the fetuses to maneuver, it is easier for them to become tangled in the cord. Single umbilical artery is also more common with twins. Most umbilical problems can be identified during pregnancy, and the health care provider should have recommendations about possible courses of action to minimize the risk of fetal demise.