ABSTRACT
The normal umbilical cord contains two arteries and one vein. A single umbilical artery occurs in around 1% of cords in singletons. Ante-natal diagnosis can be by examination of a transverse section of the cord using B-mode or by using color flow Doppler imaging of the superior vesical arteries, which are normally visualized on each side of the fetal bladder. About 20%–30% of fetuses with a single umbilical artery have associated abnormalities. The commonly reported defects are cardiovascular abnormalities, abdominal wall defects, and urinary tract abnormalities. A single umbilical artery is more commonly seen in trisomy 18, trisomy 13, and triploidy. Prenatal diagnosis of a single umbilical artery should prompt careful examination for other abnormalities, and, in particular, fetal echocardiography should be performed, as heart defects are more common. Fetal karyotyping should be considered depending on the presence of fetal abnormalities and prior risk. Serial ultrasound examination to ensure linear fetal growth should be performed in ongoing cases.
