Two-Vessel Cord: Its Causes, Risk Factors And Effects On Baby

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The umbilical cord is a three-vessel cord (having two arteries and one vein) that connects the fetus to the placenta. However, the umbilical cord undergoes irregularity in some women and becomes a two-vessel cord (having one artery and one vein). The exact cause of the formation of a two-vessel cord is unknown, but a few theories try to explain the condition. The presence of this umbilical cord may lead to certain complications, so doctors monitor such pregnancies closely to ensure the baby grows properly. Read the post to get more information on a two-vessel cord, its causes, risk factors, and effects on the 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.

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.

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. It may affect 0.5–6% of all pregnancies worldwide with a higher incidence in twin pregnancies (1).

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 (2).

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

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. In most cases, the baby is normal but in a few cases there could be problems associated with SUA.

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.

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 (3). However, in some cases, there is an increased risk of birth defects, which include (4):

  • Intrauterine growth restriction (requires serial follow-up)
  • Congenital heart problems
  • Kidney problems (postnatal urinary infection)
  • Restricted growth of the central nervous system
  • Preterm labor
  • Gastrointestinal problems
  • Edwards syndrome (Trisomy 18)

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.

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

Frequently Asked Questions

1. Does a two-vessel cord signify Down’s syndrome?

No, your uterus having a two-vessel cord does not necessarily mean your baby has Down’s syndrome. However, note that a two-vessel cord increases the risk of the baby developing Down’s syndrome. Therefore, adequate monitoring and tests are needed to determine the condition and its management (6).

2. What does an infected umbilical cord look like?

An infected umbilical cord will have the following symptoms (7):

  • Red and inflamed cord
  • Cloudy and foul-smelling discharge
  • Minor bleeding
  • Swelling in the area around the cord.

Some women may have a missing artery in the umbilical cord. If you have two blood vessels instead of three blood vessels in your umbilical cord during pregnancy, your doctor may keep you under observation. The doctor may diagnose the condition in the 18th week of pregnancy during routine scans. The condition may be more common in women carrying multiple babies or above 40 years of age. While most women with a two-vessel cord go on to have normal pregnancies, some might experience complications.

References:

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  1. Homeira Vafaei et al.; (2021); Prevalence of single umbilical artery clinical outcomes and its risk factors: A cross-sectional study.
    ttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC8261099/
  2. Yajuan Xu et al.; (2016); Association Between Isolated Single Umbilical Artery and Perinatal Outcomes: A Meta-Analysis.
    ttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC4913809/
  3. Shilpa Chetty-John et al.; (2010); Long-term physical and neurologic development in newborn infants with isolated single umbilical artery.
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3454509/
  4. Cristina Martínez-Payo et al.; (2014); Detection of Single Umbilical Artery in the First Trimester Ultrasound: Its Value as a Marker of Fetal Malformation.
    https://www.hindawi.com/journals/bmri/2014/548729/

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Subhashis Samajder

( MS, DNB)
Dr. Subhashis Samajder is a consultant Gynecologist-Obstetrician currently practising at Narayana Multispeciality Hospital, Howrah. His area of expertise includes abortion, colposcopy surgery, hysterectomy, hysteroscopy, infertility treatment, and menopausal problems. Dr. Samajder believes in sending his patients back home healthy and satisfied with the treatment. He also takes up women’s health awareness through his YT videos.

shreeja pillai

Shreeja holds a postgraduate degree in Chemistry and diploma in Drug Regulatory Affairs. Before joining MomJunction, she worked as a research analyst with a leading multinational pharmaceutical company. Her interest in the field of medical research has developed her passion for writing research-based articles. As a writer, she aims at providing informative articles on health and pharma, especially related to... more

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