Single umbilical artery refers to a condition in which there is only one artery in the umbilical cord, which can usually be determined during an NT test after 11 weeks of pregnancy. Most cases of single umbilical artery can be detected prenatally with ultrasonography. If ultrasonography reveals only a single umbilical artery without other structural abnormalities, the prognosis for the fetus is usually good. If other ultrasound structural abnormalities are also present, this indicates an increased risk of fetal chromosomal aneuploidy as well as malformations such as renal hypoplasia and vertebral defects. Abnormalities of the umbilical cord can affect the blood supply to the fetus, resulting in growth restriction or even fetal arrest. If a pregnant woman finds a single umbilical artery during a pregnancy test, she is advised to seek prompt medical attention and take appropriate treatment measures under the guidance of her doctor.