Q: What are the risks of having a Single Umbilical Artery (SUA)?

A: There are usually three vessels in the umbilical cord: two arteries and one vein. Having one, rather than two, arteries (Single umbilical artery = SUA or two-vessel cord) is the most common malformation of the umbilical cord and is seen in between 0.5% and 7% of all pregnancies. Not all studies agree on the significance of this phenomenon.

There is an about four-fold increased risk of a chromosome (gene) and other abnormalities (for example, heart, bowel, kidney, CNS) in babies with SUA. If SUA is present, the next step is usually to do a thorough ultrasound scanning to see if there are other abnormalities. An otherwise normal ultrasound is very reassuring. Some doctors suggest doing an amniocentesis to rule out a chromosome problem. Even without other abnormalities, there is an association with low birthweight and early delivery later on in pregnancy and many doctors would check the fetal growth in the latter part of the pregnancy.