True Knot in the Umbilical Cord

True Knots in Umbilical Cord
This cord had two true knots in it at placental exam.. Photo © Robin Elise Weiss

The average umbilical cord is about 50-60 centimeters and runs from the baby’s umbilicus (belly button) to the center of the placenta. During pregnancy, the baby’s oxygen, and nutrients are carried through the cord to the baby. The waste products can be carried away from the baby.

The umbilical cord is covered with a substance known as Wharton’s Jelly. The Wharton’s Jelly helps to coat and protect the umbilical cord.

It prevents the compression of the two arteries and vein that run through the cord to allow for the transport of the nutrients described above.

Sometimes the umbilical cord will get a true knot in it. This happens when the baby does its flips and turns in earlier pregnancy, causing a knot to be made in the cord, usually as there is more space to move around. The good news is that the Wharton’s Jelly tends to protect the umbilical cord from compression, even in the presence of a true knot.

True knots occur in about 1 in 2000 pregnancies, and are more common if you have an abnormally long umbilical cord, monochorionic twins, and potentially with advanced maternal age. Many of these knots are not diagnosed until after the birth upon examination of the placenta. Sometimes you will notice, during labor, that the baby is not tolerating labor as well as hoped, this may be because of the true knot or other factors.

True knots can be loose or they may be tight. The tighter the knot is, the more likely there are to be problems. You may also have more than one knot in an umbilical cord.


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Ramon y Cajal CL, Martinez RO. Four-dimensional ultrasonography of a true knot of the umbilical cord. Am J Obstet Gynecol. 10/2006;195:896-8.

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