The umbilical cord is the all-important lifeline between mother and baby during pregnancy. Together with the placenta, the umbilical cord is the pathway through which the mother supplies her baby with the oxygen and nutrients that support life and facilitate fetal growth. When problems involving the umbilical arise during pregnancy or during labor and delivery they can present very real dangers. This page will review some of the various umbilical cord problems that can sometimes develop.
The length of an umbilical cord is not something that people often think about but it is often a key factor in the development of umbilical cord issues later on. Problems can arise from a cord that is too short or a cord that is too long. At 20 weeks the umbilical cord should be around 32 cm long on average. From the point forward the cord should grow at a steady rate and by week 40 it should be about twice as long (60 cm). The diameter of the cord can also be important.
Normal umbilical cord lengths will somewhat vary depending on the height, size, and weight of the mother. Umbilical cords that are too short have been associated with various issues including lack of oxygen and nutrients and complications such as placental abruption. Short umbilical cords have also been associated with decreased utero fetal movement, fetal distress, depressed Apgar scores, low birth weight, umbilical cord abnormalities, fetal distress, and psychomotor abnormalities. If the umbilical cord is too long, it can lead to other problems and complications particularly during delivery. Long umbilical cords are more likely to result in emergency events such as fetal entanglement, cord prolapse, and true cord knots (as opposed to false knots, which are nothing). All of these events can deprive the baby of oxygen during delivery and result in serious brain injuries.
There is no question that a short umbilical cord makes the child more susceptible to a cord injury. That said, doctors are often too quick to blame a short cord for any problem the baby might have. But often a short cord is just one problem during delivery and not necessarily the sole cause of the complications or even a cause at all. There is also a tendency to exaggerate the shortness of the cord or to make assumptions about how much of the cord was cut and discarded that are not grounded in fact.
Funic presentation refers to the abnormal positioning of the umbilical cord. In funic presentation the umbilical cord is pointing down toward the cervical opening and lower segment of the uterus. The position of the umbilical cord tends to change throughout pregnancy so funic presentation is not considered a problem unless it persists after week 32 and is present when labor begins. Funic presentation at the onset of labor is considered a precursor to umbilical cord prolapse. It is a potentially serious situation that often warrants a preemptive C-section.
When the placenta and umbilical cord are first forming, it is possible for the umbilical cord to attach to the placenta in the wrong location. This condition is called abnormal cord insertion. The placenta and umbilical cord are together responsible for transporting nutrients between the mother and child. When this happens, there is sometimes an increased risk of vasa previa. The placenta may develop abnormally as well, which can be an issue for the developing fetus. High blood pressure is one possible complication.
Nuchal cord is the medical term for the situation in which the umbilical cord becomes wrapped 360 degrees around the neck of the baby inside the uterus. So there is a loop or loops of the umbilical cord around the fetal neck. When the cord wraps around the baby’s neck it usually occurs below the nuchal notch on the back of the head which is where the name comes from. Nuchal cord occurs when the baby moves around inside the uterus causes the cord to loop around the neck one or possibly more times. If a nuchal cord is too tight to be reduced, it should be clamped and cut. Struggling to attempt other maneuvers may prolong delivery and lead to birth injuries. A tight nucal cord increases the risk of spastic cerebral palsy by 300%.
The good news, however, is that nuchal cord is fairly common (10% to 29% of pregnancies) and it is usually not a dangerous condition. The umbilical cord can get wrapped around the baby’s neck several times without causing any harm at all. In fact, most babies with nuchal cord are delivered normally without any problems and the doctors simply remove the cord from around their neck after delivery. In some cases, however, nuchal cord can cause cord compression and restrict oxygen and nutrient supply to the baby. If nuchal cord complications are identified a preemptive C-section can usually avoid any potential harm to the baby.
A knot in the umbilical cord is exactly what the name implies – the cord twists around and interweaves itself into a knot. Umbilical cord knots are reported in less than 2% of all pregnancies. Most knots in the cord turn out to be relatively loose and come undone easily. However, some umbilical knots can become very tight and problematic. A particularly tight umbilical knot may prevent oxygen and nutrients from reaching the baby. A tight knot may even restrict blow flow and cause death. The infant mortality rate for a true umbilical cord knot is around 10% which means 1 in 10 babies affected by a true cord knots will die from perinatal hypoxia.
Just like nuchal cord, knots in the umbilical cord are caused by fetal movement inside the womb. Although an umbilical knot can potentially form at any time during pregnancy, there are 2 recognized danger periods during which the majority of cord knots form. The first danger period for cord knot formation is between 9-16 weeks gestation. The second danger period for knot formation is actually during the early stages of labor. There is no reliable way to predict knots in the umbilical cord but there are certain known factors that increase the risk of a knot: long umbilical cord; very active baby; older mothers; and very small baby.
Cord prolapse is the most dangerous type of complication or problem that can arise with the umbilical cord. Cord prolapse occurs with the umbilical cord drops down into the cervical opening in front of the baby instead of behind the baby. In other words, the umbilical cord comes out of the uterus and into the vagina before the fetus does. When the cord comes down first it creates a very dangerous situation because as the baby comes down behind the head of the baby will invariably compress the umbilical cord. As the baby’s head or body compresses the prolapsed cord it restricts or in some cases completely cuts off oxygen delivery to the baby through the cord. This sort of acute oxygen deprivation during childbirth can have devastating consequences for the baby. Oxygen deprivation during childbirth, even for a short time, can cause permanent brain injury resulting in lifelong disabilities such as cerebral palsy.