Abstract: Objective：To evaluate the clinical role and the ultrasonographic features in prenatal diagnosis of single umbilical artery（SUA） in Tianjin. Methods：To review 40 fetuses with SUA found in our hospital from December 2007 to July
2009 in Tianjin. Their clinical manifestation and pregnancy outcome were followed up. Results：In 40 cases，only single umbilical artery could be detected by ultrasonography. Among them，5 cases combined with other abnormalities by ultrasonography，1 case was induced of labor because of intrauterine fetal death. In the cases going on with their pregnancy，12 cases had disorders during the pregnancy course or the labor，7 cases were found to be combined with other abnormalities. Conclusions：Ultrasound-Doppler can diagnose the SUA correctly. When we find a fetus with SUA，we should analyze it from different aspect to except other organic malformations. To the cases going on with their pregnancy，we must pay more attention to the fetuses growth and delivery.

Key words: Ultrasonography, Doppler, color, Single umbilical artery, Fetus, Diagnosis