Foetal intra-abdominal umbilical vein varix is rare. Colour Doppler ultrasonography helps distinguish this vascular anomaly. A detailed anatomic scan must be performed to exclude associated anomalies: forms associated with additional complications are found in 29 to 35% of the cases. Intra-uterine foetal demise (IUFD) is a complication of umbilical vein varix. However, recent studies are more reassuring. When foetal intra-abdominal umbilical vein varix is isolated, there is no reason to change the management of the pregnancy. Foetal sonographic follow-up is recommended, focusing on an increase in the size of the varix and the appearance of a clot. A particular clinical form, connecting the umbilicus to the extra-hepatic portal vein should be known, because of a high risk of thrombosis. On the basis of this finding, postnatal monitoring by ultrasound is necessary.