How many vessels are in the umbilical cord?
Normally, the umbilical cord is comprised of three vessels (two arteries and one vein). A two-vessel cord (one artery and one vein) in isolation does not always imply a fetal abnormality, and in multiple gestations is a more common normal variant. However, detection of a two-vessel umbilical cord should prompt a search for other fetal structural abnormalities including those related to the heart. A two-vessel cord can also be associated with growth retardation and fetal aneuploidies.