KEY FACTS
Terminology
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Umbilical cord with single umbilical artery (SUA) and 1 umbilical vein (UV) instead of 2 UAs and 1 UV
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Also referred to as 2-vessel cord
Imaging
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Free loop of cord with 2 vessels instead of 3 vessels
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Color Doppler shows 1 UA adjacent to bladder
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SUA is most often isolated finding; however, it is associated with placental insufficiency (2x increased risk)
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Fetal growth restriction, maternal hypertension
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Placental anomaly association: Succenturiate lobe, velamentous cord insertion
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1/3 with fetal anomalies: Renal and cardiac most common
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Aneuploid in 10% (trisomy 18 and 13, not trisomy 21)
Clinical Issues
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Common finding: 0.5-5.0% of all pregnancies
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Follow-up for fetal growth in 3rd trimester recommended when isolated SUA diagnosed in 2nd trimester
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Genetic counseling offered if not isolated or if SUA is diagnosed in patient at increased risk for fetus with aneuploidy or genetic syndrome
Scanning Tips
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Look for number of vessels in free loop and on color Doppler bladder view
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Sometimes, 3 vessels present in free cord, but UAs fuse before entering fetus
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Look for SUA in 1st trimester if ↑ nuchal translucency
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Increases risk of aneuploidy
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Consider diagnosis if 1 UA is smaller than the other
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Hypoplastic UA is variant of SUA
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Carries same risks and associations
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SUA is often larger than UA in a 3-vessel cord
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Carries all fetal blood to placenta
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has a thicker wall than the umbilical vein (UV) 
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. No other anomalies were seen, and fetal growth was normal. Isolated SUA is a common finding. Note that the SUA is almost the same diameter as the UV. This is not surprising, since the SUA is carrying all the fetal blood to the placenta.Related posts:
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