Two-Vessel Cord: What Is It And Does It Pose Any Risk To The Baby?

Umbilical Cord

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It is the source of life for your baby. The umbilical cord is a conduit connecting the fetus to the placenta. It carries oxygen and nutrients from the placenta to the fetus’ bloodstream.

In short, it is the means through which you send your baby the nutrients required for their development. So, what happens if such an important connection between you and your baby turns to be abnormal?

Momjunction explains the most prominent umbilical cord abnormality and how it can affect your baby.

What Is A Normal Umbilical Cord?

The formation of an umbilical cord begins during the fifth week. It measures around 20in (50cm) in length (1).

Normally, an umbilical cord has two arteries and one vein. It is also known as a three-vessel cord, which is covered by a thick gelatinous substance called Wharton’s jelly.

Here’s what the blood vessels in the umbilical cord do:

  • The vein carries nutrients and oxygen from the mother to the fetus.
  • The arteries carry the waste products like carbon dioxide and deoxygenated blood away from the fetus to the mother’s bloodstream, to eliminate them through the mother’s kidneys.

In some cases, complications arise due to a change in the number of blood vessels in the cord. One such abnormality is a two-vessel cord.

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What Is A Two-Vessel Cord?

In a two-vessel cord, there is one vein and just one artery instead of two. It is also called single umbilical artery or SUA. This occurs in less than 1% of singleton pregnancies and 6-11% of multiple pregnancies (2).

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What Causes This Umbilical Cord Abnormality?

Though the exact cause of two-vessel cord is not known, there are two theories around it.

As per one theory, this condition arises because one of the two arteries stops to grow inside the womb, while another theory suggests improper splitting of the artery into two (3).

As mentioned earlier, this condition occurs in less than 1% of singleton pregnancies but some women are at a higher risk than others.

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[ Read: Twin Pregnancy Complications ]

What Are The Risk Factors For A Two-Vessel Cord?

Here are the factors that could make a woman susceptible:

  • Pregnancy after 40 years of age
  • Pregnant with a girl
  • History of diabetes or episodes of high blood sugar
  • Caucasian women
  • Multiple pregnancies
  • Smoking

However, this condition can arise even without any risk factors.

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How Is A Two-Vessel Cord Diagnosed?

The SUA can be detected during an ultrasound scan. Usually, the doctors check for the umbilical arteries during the 18th week of gestation. A color-flow Doppler ultrasound can help detect this abnormality earlier. It is usually done in the 14th week.

The doctors also assess the problem by checking:

  • Your family and personal medical history
  • Fetal echocardiogram to check the functioning of the fetal heart
  • Genetic abnormality screening such as an aneuploidy screening

One or more of these tests will detect the problem and help you know if it is going to affect the baby.

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Does Single Umbilical Artery Pose A Risk To The Baby?

SUA need not necessarily harm your baby. In some cases, it doesn’t result in any complications (4). However, in some cases, there is an increased risk of birth defects, which include (5):

  • Intrauterine growth restriction
  • Congenital heart problems
  • Kidney problems
  • Restricted growth of the central nervous system
  • Preterm labor
  • Gastrointestinal problems

If the doctor finds no adverse effects of the two-vessel cord on the baby, then it is called an isolated single umbilical artery. In such a case, another ultrasound is recommended in the later weeks to see if the baby is growing in proportion to their gestational age.

[ Read: Preterm Labor: Causes, Signs ]

If the ultrasound findings indicate other abnormalities, the doctor suggests an amniocentesis (a sample of amniotic fluid is tested for congenital abnormalities in the fetus). If the baby is born with organ dysfunction, then extra care is provided in the NICU.

What is reassuring about SUA is that most babies are born healthy. If the doctor tells you that there is no complication, then stay relaxed. However, if there are complications, you can rely on the medical advancements to have your little one safely in your hands.

Do you have any experience to share? Let us know about it in the comment section below.

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shreeja pillai

Postgraduate in Chemistry and content writer. She has worked as a research analyst with a leading multinational pharmaceutical company and also holds a diploma in pharmaceutical regulatory affairs. Her interest in the field of medical research has developed her passion for writing research-based articles. She is a writer for MomJunction and aims at providing informative articles based on health and wellness. Apart from writing, she takes a great interest in music and traveling. know more about her at
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