Two-Vessel Cord (Single Umbilical Artery) – Diagnosis and Treatment

When in the womb, your baby is connected to you through the umbilical cord and placenta. Oxygen, nutrients and essential blood supply reach the baby’s bloodstream through the umbilical cord, which normally has three blood vessels; two arteries and one vein. However, sometimes, there are abnormalities in the umbilical cord. They can be shorter than the normal or longer, and at times, there could be a two-vessel umbilical cord instead of a normal one. Understanding the abnormality that occurs in this important link between you and the baby can help you take steps to prevent or handle it efficiently. In this article, we shall talk about the two-vessel umbilical cord abnormality and also look into its possible causes, risks and diagnosis. But first, let’s understand what a normal umbilical cord is and what its functions are.

What Is a Normal Umbilical Cord?

A normal umbilical cord will have two arteries and a vein forming a three-vessel cord. It is covered with Wharton’s Jelly, which is a gelatinous substance and is about 20 cms in length.  The important functions of these blood vessels are as follows:

• The arteries carry the waste products like deoxygenated impure blood and carbon dioxide from the foetus to the mother’s bloodstream, which is then eliminated through the mother’s kidneys.
• The vein carries nutrients and oxygen from the mother to the foetus.

Now, let’s understand what a two-vessel umbilical cord is and the factors associated with this condition.

What Is a Two-Vessel Umbilical Cord?

Sometimes during the development of the baby, an abnormality occurs, and only one artery and a vein are present. The umbilical cord is then called a two-vessel umbilical cord or single artery umbilical cord (SUA).

How Common Is It?

Less than 1% of single pregnancies and about 6-11% of multiple pregnancies have this condition. Although the exact cause is unknown, the condition could occur either due to the improper splitting of cells when forming the umbilical cord (around the 5th week of pregnancy) or due to improper formation of the second artery.

Causes and Risk Factors of Single Umbilical Artery (SUA)

As explained above the exact cause of SUA is unknown, and depends on the way the arteries split and form during pregnancy.

The risk factors contributing to the formation of SUA are:

• Being a Caucasian woman
• Becoming pregnant after 40 years of age
• Having had diabetes or high blood sugar levels during the timeline of the pregnancy
• Multiple pregnancies
• Being pregnant with a girl child

How Is a Single Umbilical Artery (SUA) Diagnosed?

The attending doctors assess the risks for this condition through an ultrasound, especially the Doppler ultrasound. In most cases, the medical history of the mother and the family, and prenatal tests help the doctor deduce the possibility of or presence of an SUA.  Here are the tests carried out to diagnose the condition:

• Foetal echocardiogram
• Genetic abnormality screening or aneuploidy screening
• Colour Flow Doppler Ultrasound

These tests can detect the problem and determine if your baby will be affected. Mothers who are at risk of developing a two-vessel umbilical cord abnormality are asked to undergo a colour flow Doppler ultrasound scan around the 14th week of pregnancy. Ultrasound scans are normal in the 18th week of gestation to help detect a two-vessel cord.

Can a Single Umbilical Artery (SUA) Affect Your Baby?

While in some cases there are no complications, in others there are risks involved. The condition could affect foetal development and lead to birth abnormalities. Single umbilical artery complications do not necessarily harm your baby.  However, certain risks that the baby is exposed to are:

• Preterm labour
• Restricted growth of the central nervous system
• Congenital heart problems in the baby
• Kidney problems in the baby
• Gastrointestinal problems in the baby
• Intrauterine growth restriction (IUGR)
• High risk of the genetic abnormality known as VATER – vertebral defects, anal atresia, trans-oesophageal fistula with oesophagal atresia, and radial dysplasia.

How Is a Single Umbilical Artery (SUA) Cord Treated?

The doctor will monitor the baby’s growth through ultrasound scans, even if there are no complications. When the low-speed ultrasound findings indicate the possibility of SUA, a high-speed ultrasound will be done. If the baby is diagnosed to have a single umbilical artery or other abnormalities, an amniocentesis, where the foetus is tested for congenital abnormalities using a sample of amniotic fluid, is done. High-Speed Doppler Ultrasound scans and colour flow scans could also be scheduled to view the baby’s development. If the baby is born with organ dysfunction, additional monitoring is performed in the NICU.

Can You Prevent Single Umbilical Artery?

So far, there is no way to prevent single umbilical artery, but since there are certain risk factors that increase its possibilities and associated anomalies, a mother-to-be should:

• Quit smoking
• Discuss risk factors that may lead to SUA with the doctor
• Regularly attend appointments with the doctor
• Report any untoward symptoms to the doctor
• Educate herself and take an informed decision on her delivery

Educating yourself and being able to make an informed decision is the best way to go for mothers. Remember that the phenomenon of two-vessel umbilical cord complications is rare. Even if present, it may not affect your baby. Always discuss your fears and concerns with your doctor and make an informed decision.

References and Resources:

• Wikipedia
• Healthline