A single umbilical artery is detected during a major screening test, usually between 22 and 24 weeks of pregnancy. The umbilical cord of a normal fetus is composed of one umbilical vein and two umbilical arteries. If only one artery is found inside the umbilical cord, it is known as a single umbilical artery. Single umbilical artery will affect the blood, oxygen, and nutrient metabolism of the fetus, which may result in intrauterine hypoxia and growth restriction. Single umbilical artery is usually detected during the ultrasound examination of the obstetrics department of the major screening, around 22 to 24 weeks of pregnancy. If the single umbilical artery is detected on ultrasound and there are no other structural anomalies, the prognosis is generally good, and the development of the fetus should be reviewed regularly. If there is a combination of other structural anomalies, chromosomal screening and active intervention are required.