A nuchal cord occurs when the umbilical cord wraps around a baby's neck while they are still in the womb. This can occur during pregnancy, labor, or delivery. It can be detected via ultrasound with relative accuracy, although this condition is rarely serious and typically requires no intervention other than additional fetal heart rate monitoring during labor. Nuchal cords are not without risk, however. While type A nuchal cords, occurring in 37% of pregnancies, are common and typically harmless, type B nuchal cords can cause a knot to form in the umbilical cord, which can restrict blood flow to the baby, thereby restricting oxygen.
As a fetus grows larger inside the womb, space eventually becomes very limited. This, coupled with the common gymnastics that unborn babies like to perform, can cause the umbilical cord to wrap around the baby's neck. While some may believe this could potentially choke the baby, this is generally not the case. Babies receive oxygen through the cord itself and do not breath through the nose or mouth until after they have left the womb.
The only concern with a nuchal cord is the cord itself being stretched too far, thus limiting blood flow and oxygen. Umbilical cords are structured to withstand this type of stretching, however, making complications from a nuchal cord extremely rare. The only time excessive stretching of the cord is concerning is when the cord is wrapped multiple times around the neck. This, however, only occurs in less than 5% of all nuchal cord cases. A ultrasound can detect a nuchal cord that develops during pregnancy in 90% of cases, although it is difficult to tell how many times the cord is wrapped around the baby's neck.
A nuchal cord can also develop during early labor when the baby moves through a loop in the cord to make its way to the birth canal. In the same manner, this can also occur during labor when the baby is exiting the birth canal. As most women with low risk pregnancies seldom undergo an ultrasound prior to delivery, doctors and soon-to-be moms typically do not know the cord is around the baby's neck until after it is born. In this case, it can simply be unwrapped and, in most cases, business proceeds as usual.
The main complication of a nuchal cord is when the wrapping of the cord turns into a knot. This is known as a type b nuchal cord, and can cause blood flow restriction if it is tight enough to cut off the circulation in the cord. If it develops early enough in pregnancy, and again is tight enough, it can also cut off the baby's food supply. While a knot becoming tight enough to cause these complications is rare, it is a concern and may require early delivery of the baby if the pregnancy is far enough along. Nuchal cords are nonetheless a common part of pregnancy, is of no fault of the mother, and rarely causes fetal death or any other health complications for the baby.