Two Vessel Cord: Causes, Risk Factors and Diagnosis


In the womb, a baby is connected to the mother through an umbilical cord and placenta. Oxygen, nutrients, and essential blood supply reach the baby through the umbilical cord. Normally there are three blood vessels in an umbilical cord, two arteries, and one vein.

The following article explains the causes, risk factors, diagnosis, and treatment of a two-vessel cord.

What is a normal umbilical cord?

A normal umbilical cord forms a three-vessel cord containing two arteries and a vein. An umbilical cord is covered by a gelatinous substance known as Wharton’s jelly and its length is about 50-60 cms at birth. The functions of these blood vessels are as follows:

  • Deoxygenated impure blood and carbon dioxide from the fetus to the mother’s bloodstream is carried by the arteries.
  • Nutrients and oxygen from the mother to the fetus are carried by the veins.

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

What is a two-vessel umbilical cord?

There are several abnormalities of umbilical cord including an umbilical cord that’s too short or long. Sometimes an abnormality occurs during the development of the baby, in which only one artery and a vein are present. This is known as a two-vessel umbilical cord or single artery umbilical cord (SUA).

Two Vessel Cord: Causes, Risk Factors and Diagnosis


How common is it?

This is more common in multiple pregnancies, in single pregnancy chances are less than 1% whereas in multiple pregnancies chances are 6-11%. The exact cause of this condition is not known but the condition could occur due to a variety of causes, which are as follows:

  • When there is primary agenesis of one umbilical artery.
  • When there is secondary atresia or atrophy of a previously normal umbilical artery.
  • If there is the persistence of the original allantoic artery of the body stalk.

Causes and risk factors of single umbilical artery (SUA)

As mentioned above the exact cause of SUA is not known, it depends on the way arteries spit and form during pregnancy. Some theories explain the cause of SUA. According to one theory, an artery doesn’t grow properly in the womb and another suggests that the artery doesn’t divide in two as it divides normally.

Risk factors of the two-vessel cord are as follows:

  • Being a caucasian female
  • Pregnancy after 35 years of age
  • Pregnancy with a girl
  • History of diabetes or high blood sugar levels during pregnancy
  • Multiple pregnancies like twins or triplets
  • Use of medications which affect fetal growth, like phenytoin

These risk factors don’t guarantee that a mother will surely have a baby that has a two-vessel cord.

Diagnosis of two-vessel cord

Doctors assess the risk of this condition through an ultrasound, especially the Doppler ultrasound. The tests which are carried out to diagnose the condition are as follows:

  • A fetal echocardiogram (in which the chambers and working of the fetal heart is viewed)
  • Colour Flow Doppler Ultrasound
  • Screening tests are done for genetic abnormalities in pregnancy, like an aneuploidy screening

If a baby is affected then these tests can detect the problem. Around the 14th week of pregnancy mothers who are at risk of developing a two-vessel cord, an abnormality is asked to undergo a color flow Doppler ultrasound scan. The position of a baby makes it hard for the doctor to fully view the cord.


Can a Single Umbilical Artery Affect a Baby?

In some cases, no complications are there, but on the other hand, there are some risks involved. This can affect fetal development and lead to birth abnormalities. Complications of this do not necessarily harm the baby. But, certain risks that the baby is exposed to are:

  • There can be preterm labor
  • Growth of the central nervous system is restricted
  • Congenital heart problems
  • Kidney problems
  • Gastrointestinal problems
  • Intrauterine growth restrictions
  • High risk of VATER which is a genetic abnormality and which stands for vertebral defects, anal atresia, transoesophageal fistula with oesophageal atresia, and radial dysplasia.

Treatment of Single Umbilical Artery (SUA)

Baby’s growth is monitored by the doctor through ultrasound scans, even if there are no complications. A high-speed ultrasound will be done when the low-speed ultrasound findings indicate the possibility of SUA. An amniocentesis is done if the baby is diagnosed to have a single umbilical artery or other abnormalities. In amniocentesis, the fetus is tested for congenital abnormalities using a sample of amniotic fluid. To view the baby’s development high-speed Doppler ultrasound scans and color flow scans could also be scheduled. Additional monitoring is performed in NICU if the baby is born with organ dysfunction.

Prevention of Single Umbilical Artery

There is no way to prevent single umbilical artery, but the risk factors that increase its possibilities can be reduced, for this, a mother should :

  • Quit smoking
  • She should discuss the risk factors that may lead to SUA with her doctor
  • Regularly attend all the appointments
  • She should report to her doctor if she notices any untoward symptoms
  • Educate herself

A mother should remember that the complications of a two-vessel umbilical cord are rare. And if present, it may not affect the baby. A mother should always discuss her fears and concerns with her doctor and make an informed decision.


Some more tests are required if the doctor has diagnosed the baby with a two-vessel cord. In some babies, there are no complications as a side effect of a two-vessel cord.


A doctor and possibly a genetic specialist can help to determine the steps and diagnose the baby and should start treatment as soon as possible. So, a woman should not fear anything and she should consult her doctor immediately if she notices some unusual symptoms.