These are the serial scans of a 28-year-old woman G1,  with no significant past medical history. The finding is a large cystic anterior abdominal structure that fills with Doppler signal:

A diagnosis of Umbilical vein varix was made. This woman had a premature rupture of membranes at 34 weeks. A C-section was performed and a baby boy weighing 2640 gm was delivered.