Single umbilical artery (SUA):

  • In the umbilical cord, there are 2 umbilical arteries and one umbilical vein. The vein carries oxygenated blood and nutrition from the placenta to the baby and the arteries carry deoxygenated blood and metabolic waste from the baby back to the placenta;
  • However, in some fetuses, there is only one umbilical artery and one umbilical vein. It is called ‘single umbilical artery (SUA)’, and sometimes it is labelled as ‘1A1V’;
  • SUA is present in 0.5% of fetuses and can be a normal variant;
  • There is an association with other structural abnormalities in 40% of cases, with defects reported among urogenital, gastrointestinal, cardiovascular, respiratory and central nervous systems;
  • There is also a weak association with chromosomal abnormalities especially Downs and Edwards syndromes;
  • For isolated SUA, antenatal screening with OSCAR or NIPT test is considered adequate. An amniocentesis is not advised, unless the couple wants a 100% certainty on the fetal karyotyping;
This article is contributed by Dr. T.N. Danny Leung
Updated on 25.09.2020