This document discusses anomalies of the fetal venous system. It begins with a classification system that expands on the four major embryonic venous systems (umbilical, vitelline, cardinal, pulmonary). It then reviews etiology and sonographic appearance of anomalies in these systems. Specifically it discusses heterotaxy syndromes affecting the cardinal veins, anomalies of the umbilical veins including agenesis of the ductus venosus and persistent right umbilical vein, and classification of these anomalies. Outcomes are discussed for different venous anomalies depending on associated malformations. Precise prenatal diagnosis of venous anomalies is possible using ultrasound.