Introduction
It is uncommon for a knot to form in the umbilical cord during pregnancy or delivery, and it often goes unnoticed as there are usually no symptoms. Fortunately, most babies are born without any issues. However, there is a risk of complications such as brain damage or stillbirth. The umbilical cord knots are usually harmless and can untangle on their own. However, if the knot becomes too tight (true knots), it can block oxygen and nutrients from reaching the fetus, causing complications during pregnancy and delivery. While true knots are rare, they can be serious and require medical attention. In most cases, babies are born healthy despite knots in the umbilical cord.
What Is an Umbilical Cord?
The placenta, which forms during pregnancy, connects to the umbilical cord. It transfers blood, oxygen, and nutrients from the mother to the baby. Inside the womb, the baby relies on the umbilical cord for breathing since their lungs are not yet functional. The umbilical cord carries deoxygenated blood from the baby to the placenta.
The baby's umbilical cord consists of three layers of muscle:
-
The outer layer (tunica externa) is elastic and dense, protecting the cord.
-
The middle layer (tunica media) contains most of the blood vessels and helps regulate the baby's blood flow and blood pressure.
-
The inner layer (tunica internal) is composed of connective tissue, this layer is at the core of the cord. It contains valves that control blood flow, ensuring deoxygenated blood goes to the placenta and oxygenated blood returns to the baby.
What Is an Umbilical Cord Knot?
An umbilical cord knot is a knot in the baby's umbilical cord. Most knots do not harm the baby and are formed during pregnancy or delivery. Wharton's jelly protects the blood vessels in the cord, reducing the chances of a tight knot. If the knot remains loose, it does not harm the baby. However, if it becomes tight, it can interfere with blood circulation and cause oxygen deprivation, although this is rare.
Pregnancy care providers are aware of the factors that increase the risk of a true knot and the signs to look out for. They also understand that some knots occur naturally due to fetal movement. Additionally, the pressure from labor and delivery can further tighten a knot.
While small knots are usually not a cause for concern, if a knot tightens into a true knot, it can lead to complications as it compresses the umbilical cord tightly and deprives the fetus of oxygen.
Umbilical cord knots (entanglements) have the potential to cause a decrease in blood and oxygen supply to the fetus, leading to fetal distress, growth limitations, or even stillbirth in severe instances. However, numerous pregnancies with umbilical cord entanglements have favorable outcomes.
What Causes an Umbilical Cord Knot?
During pregnancy, the baby's movements can be felt throughout the day. As they stretch and explore their confined space in the womb, the cord can become tangled. Cord knots are more likely to occur in the early stages of pregnancy when the baby is smaller and has more space to maneuver. Certain factors can also increase the likelihood of a cord knot. They are:
-
Two babies in a single sac (identical twins).
-
Insufficient amniotic fluid in the womb.
-
An umbilical cord longer than normal.
-
Baby is smaller than the average size, providing extra space for movement.
-
Male fetuses.
-
Gestational diabetes mellitus.
-
Monoamniotic twins (twins with the same amniotic sac).
How Common Is an Umbilical Cord Knot?
Approximately one out of every 100 pregnancies experience the presence of a knot in the umbilical cord. It is important to note that not all of these knots are considered to be "true" knots. True knots are a rare occurrence, happening in less than one percent of all pregnancies.
Who Is at Risk for Developing Umbilical Cord Knots?
Babies who have long umbilical cords or are small for their gestational age have a higher risk of developing true knots. Some umbilical cord knots occur naturally and may have no known risk factors. However, certain factors can increase the likelihood of a true knot. Factors that can contribute to this, include the fetus being smaller than expected for its gestational age, having an unusually long umbilical cord, carrying identical twins that share an amniotic sac, having an excessive amount of amniotic fluid, having had two or more pregnancies, or being over the age of 35.
How Are Umbilical Cord Knots Managed in Pregnancy?
-
Doctors cannot treat an umbilical cord knot, and there is not anything one can do to prevent it from happening. However, identifying a knot and closely monitoring the baby can aid in a healthy delivery and avoid potential injury to the baby.
-
If a knot is detected on an ultrasound before delivery, closer monitoring may be necessary in the third trimester. If a knot is detected during delivery, the fetus must be closely monitored for distress, as contractions can make the knot tighter. In rare cases, an emergency C-section may be necessary. However, true knots are rare and typically do not cause permanent harm.
-
If a doctor identifies a knot on an ultrasound, they may ask the mother to come in for more frequent ultrasounds and monitoring. They will check for adequate growth and a strong heartbeat, both signs that the baby is thriving in the womb.
Conclusion
Not all umbilical cord knots have complications, and many pregnancies with this condition proceed without complications. Healthcare providers will monitor the pregnancy and take appropriate measures to ensure the well-being of both the baby and the mother. The management of umbilical cord knots will vary depending on individual circumstances. Since knots are uncommon, it is not necessary to worry about them during pregnancy. If the healthcare provider confirms a healthy pregnancy and normal fetal growth, the chances of experiencing a complication like a true knot are very low.
