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Isolated Single Umbilical Artery (SUA)

A two-vessel umbilical cord

The umbilical cord carries blood between your baby and the placenta. The placenta gives oxygen and food to your baby.

Most cords have one large vein and two small arteries.

With SUA, the cord has one vein and one artery.

Isolated means the detailed ultrasound did not find another problem, poor growth, or another soft marker.

Comparison of a normal three-vessel umbilical cord with one vein and two arteries and a two-vessel cord with one vein and one artery.
A normal cord has three vessels. An SUA cord has two vessels.

What happens first?

  • a detailed ultrasound checks your baby from head to toe
  • the heart, kidneys, spine, arms, legs, stomach, bladder, and growth are checked
  • if another finding is seen, your care plan may change

Chromosome testing

  • SMFM does not advise more testing for chromosome problems just because isolated SUA is found
  • this is true if an earlier screening test was low risk or if you chose no screening
  • testing may still be offered for another reason or because you want it

Special heart scan?

  • usually not, if clear heart pictures looked normal on the detailed ultrasound
  • a fetal echo is a special ultrasound of the baby's heart
  • it may be advised if the heart was not seen well, looks different, or there is another reason

Growth check

  • SMFM advises an ultrasound in the last three months of pregnancy
  • this scan checks how your baby is growing
  • your care team will choose the best time

Checks near the due date

  • starting at 36 weeks, your care team may check your baby's well-being once a week
  • this may be a heart-rate test or an ultrasound test
  • your plan may differ if another pregnancy problem is present

What should I remember?

SUA is an ultrasound finding. It is not a diagnosis.

If poor growth or another problem is found later, your care plan may change.

Educational use only. This handout does not replace advice from your pregnancy care team.
Medical references used for this handout
  1. Society for Maternal-Fetal Medicine; Prabhu M, Kuller JA, Biggio JR. Consult Series #57: Evaluation and management of isolated soft ultrasound markers for aneuploidy in the second trimester. Am J Obstet Gynecol. 2021;225:B2-B15. Reaffirmed 2025. SMFM guideline.
  2. Carvalho JS, et al. ISUOG Practice Guidelines (updated): fetal cardiac screening. Ultrasound Obstet Gynecol. 2023;61:788-803. ISUOG guideline.
  3. Moon-Grady AJ, et al. Guidelines and Recommendations for Performance of the Fetal Echocardiogram: An Update from the American Society of Echocardiography. J Am Soc Echocardiogr. 2023;36:679-723. ASE guideline.
  4. Solomon BD. VACTERL/VATER Association. Orphanet J Rare Dis. 2011;6:56. Open-access review.