Abstract: Objective：To explore the proportion of the absence of umbilical artery (AUA) in singleton pregnancy and its correlation with the fetal malformations of various systems. Methods：Data of 130 cases of singleton pregnancies confirmed as single umbilical artery (SUA) by postpartum pathology were retrospectively analyzed. According to the results of prenatal ultrasound examination, they were divided into the left AUA group and the right AUA group, and the incidence of malformations of different systems between the two groups was compared. Results：The incidence of SUA in singleton pregnancy was 0.59% (130/22 055). Among the 130 cases of SUA, the incidence of isolated SUA was 70% (91/130) and the incidence of non-isolated SUA was 30% (39/130). Among them, 30 cases (30/130, 23.1%) complicated with cardiovascular malformations were the most common. Among the 130 cases of SUA, there were 82 cases of left AUA and 48 cases of right AUA (63.1% vs. 36.9%); The incidence of multiple malformations and complex cardiovascular malformations in the left AUA group was significantly higher than that in the right AUA group (24.4% vs. 8.3%, P=0.023; 23.2% vs. 6.3%, P=0.013). Conclusions：In singleton pregnancy with SUA fetus, the left AUA is more common，and it is more likely to be associated with multiple malformations and complex cardiovascular malformations.

Key words: Single umbilical artery, Pregnant women;, Umbilical arteries, Prenatal diagnosis;, Ultrasonography, prenatal;, Congenital abnormalities