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A true knot in the umbilical cord is a rare complication of pregnancy or delivery. Typically, there are no symptoms and most people aren’t aware there’s a knot in their umbilical cord. In most cases, your baby is born healthy. But complications like brain damage or stillbirth are possible.
Knots in the umbilical cord are similar to knots in your shoelace. Just like your shoelaces can become knotted, the umbilical cord can knot. Small knots usually don’t pose a threat to the fetus and often “unknot” on their own. They happen naturally from the fetus moving around. A gel-like substance called Wharton’s jelly prevents small knots from getting tight.
But, sometimes, the knot gets very tight, and healthcare providers call this a true knot. Unlike a small knot that loosens easily, a true knot is so tight that it can block oxygen and nutrients from reaching the fetus. It can cause complications during pregnancy and delivery because it deprives the fetus of these vital substances.
True knots are rare and don’t usually cause pregnancy complications. In most instances, your baby is born healthy.
The umbilical cord goes from the placenta to the fetus and is vital to the growth of the fetus. The cord is the vessel that gets the oxygen and nutrients from the placenta to the fetus. The cord also transfers waste from the fetus back into the placenta.
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About 1 in 100 pregnancies have some type of knot in the umbilical cord. Not all knots are “true” knots. True knots occur in less than 1% of all pregnancies.
Pregnancy care providers don’t know the exact cause, but they do know what factors increase a person’s risk of a true knot and what signs to look for. They also know that some knots happen naturally because the fetus moves around. Additionally, the pressure from labor and delivery can further tighten a knot.
Small knots aren’t usually a cause for worry. But if the knot tightens into a true knot, it has the potential to cause complications because it’s compressing the umbilical cord so tightly and depriving the fetus of oxygen.
Your provider watches for signs of a true knot, especially when you have one or more risk factors. It’s important to note that you didn’t cause a knot to form and it’s not your fault.
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Some umbilical cord knots happen naturally and you may have no known risk factors. But healthcare providers know that the following factors may increase your chances of getting a true knot:
A true knot can prevent oxygen and nutrients from reaching the fetus, which it needs to survive.
The best way to think of a true knot is to imagine a garden hose with a knot in it. Knots restrict the water from flowing out of the hose. This is what can happen with a true knot. In both cases, the substance you need to pass through doesn’t flow freely.
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True knots in the umbilical cord can cause serious complications because they cut off a fetus’s oxygen supply. The long-term effects of a knot depend on how tight it was. A tight knot could cause severe hypoxia or become fatal to the fetus. A looser knot may cause mild hypoxia and not cause long-term damage.
Some of the long-term effects of umbilical cord true knots include:
Yes, a true knot can cause stillbirth. But, most pregnancies and deliveries end in a healthy baby.
You often don’t know you have a true knot until delivery. But, some people notice less movement in the third trimester, which can be a risk factor for a true knot. This is one of the reasons why it’s important to let your provider know if you don’t feel the fetus move.
Pregnancy care providers can diagnose a true knot through ultrasound during pregnancy after noticing a decrease in the fetus’s heart rate or movement patterns. But seeing a true knot on a prenatal ultrasound is very difficult, which is why a diagnosis often comes after your baby is born.
Sometimes, a provider detects a true knot during labor and delivery when there’s a sudden change in the fetus’s heart rate. In these cases, your provider must act quickly and decide whether vaginal delivery is still safe.
Pregnancy care providers can’t treat true knots by loosening them. The key to managing a true knot is to be aware of the risk factors and watch for complications if a person has a risk factor.
If your provider notices a knot on an ultrasound before delivery, they’ll monitor your pregnancy more closely, especially in the third trimester. This could include additional ultrasounds, Doppler studies and assessments of fetal growth and fetal movement.
But, if your provider detects a knot in the umbilical cord during delivery due to changes in fetal heart rate, they’ll need to monitor the fetus very closely to watch for fetal distress. If you have a true knot in the umbilical cord, the contractions from childbirth can actually make the knot even tighter. This is why your provider needs to watch the fetus’s heart rate closely as your labor progresses. An emergency C-section may be necessary if the fetus appears to be in distress or without oxygen.
While it can be a scary situation, true knots are rare and shouldn’t cause permanent harm if they do happen.
A note from Cleveland Clinic
True knots in the umbilical cord are rare. While they may lead to complications, they usually don’t, and most babies are born healthy. Since knots don’t happen often, try not to worry about them throughout your pregnancy. If your pregnancy care provider says your pregnancy is healthy and the fetus is growing, the chances of you having a complication like a true knot are very low. Try to focus on taking care of yourself. Talk to your provider if you do have questions or concerns about your pregnancy.
Last reviewed on 05/09/2023.
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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy