There are 4 types of single umbilical artery (SUA), based on pathogenesis. The incidence of SUA is up to 1% of all singleton fetuses, and up to 4.6% of twins. SUA can occur either as an isolated finding or as part of a congenital anomaly syndrome. In this session we will review the pathogenesis, identification of, fetal work-up, and patient management of SUA. Data from the SMFM, and ACOG.