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Single Umbilical Artery

The umbilical cord usually has three vessels: a two-artery vein supplying the baby with oxygen-rich blood, and one vein returning oxygen-poor blood and waste to the mother's circulation. But up to two percent of unborn babies have a single umbilical artery (SUA, also known as a "two-vessel cord.")

Causes of SUA

  • Another umbilical artery never forms.
  • The umbilical cord initially has two arteries, but one is lost during development.
  • In some babies, SUA can be associated with a chromosome problem, genetic syndrome, or other birth defect.

Impact on unborn babies

  • Most babies with SUA do not have other birth defects or developmental issues, but they may be at higher risk of being born early or having a low birthweight.
  • Some babies with SUA will have other birth defects, such as heart or kidney problems.
  • If SUA is not the only abnormality discovered on an ultrasound, the baby is more likely to have a chromosome problem such as trisomy 18 or Down syndrome.

Further testing

  • You can have a more detailed ultrasound to look for other abnormalities.
  • An amniocentesis can diagnose a chromosome abnormality very accurately. Amniocentesis involves obtaining a sample of the fluid surrounding the baby, which is then used to study the fetal chromosomes. There is a small risk of miscarriage from amniocentesis.
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