What is a 3 Vessel Cord?

A Tour of the Umbilical Cord

Doctor holding a placenta
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Question: What is a three vessel cord?

Answer: Let's start with the basics of the umbilical cord. The umbilical cord is the connection between your baby and the placenta. A normal umbilical cord has two arteries and one vein, this is known as a 3 vessel cord. It is covered by a thick gelatinous substance known as Wharton's Jelly. The vein brings in oxygen and nutrients to the baby from the mother. The arteries are used to transport waste away from the baby to the mother via her kidneys.

The umbilical cord starts to form early in pregnancy, around the fifth week of gestation. It will get longer and take the famous coil shape as it does. The average length of an umbilical cord is about 22 to 24 inches.

Placental Exam and Umbilical Cord Via Ultrasound

If you are having a mid-pregnancy ultrasound, also known as a fetal anatomy survey, your ultrasonagrapher will examine the placenta. They are looking for many things. They will try to see both the arteries and vein during your exam. This is easier done with color Doppler ultrasounds, but can be done with your average ultrasound machine. They may or may not say anything with the exam. The size and location of the placenta and umbilical cord will be noted.

Wharton's Jelly and Knots in the Umbilical Cord

The Wharton's Jelly is very thick and helps protect the arteries and vein from being compressed during your pregnancy as your baby grows and the cord gets pressed and even potentially knotted in about 1% of all births.

This is more common in identical twin pregnancies or if your baby's umbilical cord is longer than normal. Most knots remain loose and do not pose a threat to your baby, but it is believed to be the cause about 5% of stillbirths. Fetal monitoring is one method used to look for cord anomalies, and when certain heart rate changes occur, a cesarean birth may be the best option for your baby.

Umbilical Cord Cysts

Umbilical cord cysts found in only about 3 percent of cords. There are two main types: true cysts and false cysts. False cysts are related to the Wharton's Jelly and filled with fluid. True cysts contain what's left over from early parts of the pregnancy. Since the cysts can be associated with birth defects, your doctor or midwife may recommend further testing including an amniocentesis to check for a cause. Many times these are not found until after birth.

Single Umbilical Artery

About 1% of all babies will have a two vessel umbilical cord, which is a single artery (Single Umbilical Artery) rather than two. You will also see this in about 5% of pregnancies where there is more than one baby (twins, triplets, etc.). When this is found, you should be referred for a more detailed ultrasound. The reason that another ultrasound is done is to double check the findings and to ensure that your baby does not have any abnormalities. About 20% of babies who only have one artery in the umbilical cord will have malformations.

Vasa Previa

This is where a blood vessel from the cord is not protected by the Wharton's Jelly and actually cross the cervix. This can lead to the tearing of the vessel during birth, dilation, or even simply pressure at the end of pregnancy. It is a very serious complication. Thankfully it is fairly rare occurring only 1 in 2500 births. Early diagnosis via ultrasound is the key to safe birth for this pregnancy. When diagnosed earlier in pregnancy, and a cesarean is typically done around week 35 to prevent damage to the vessel. Typically you may see painless bleeding in the second or third trimesters or it is picked up at a routine ultrasound.

Velamentous Insertion

A velamentous insertion of the cord means that it inserts into the actual membranes rather than the center of the placenta. This leaves the vessels exposed in places, making it possible for them to become compressed as the baby gets bigger.

The good news is that the vast majority of the time there are no complications with the umbilical cord. It is a fascinating structure that works with the placenta and baby.


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