Absence of the ductus venosus.

Absence of the ductus venosus is a rare vascular anomaly, but clinicians should be aware that it can be diagnosed antenatally and the prognosis is dependent on the type of associated malformation of the fetal vascular system. Antenatal detection of a single umbilical artery and unexplained cardiomegaly should prompt detailed examination of the umbilical and portal veins. Absent ductus venosus is associated with three main patterns of abnormal venous circulation, the worst prognosis being seen when the umbilical vein bypasses the liver and connects to the right atrium. Fetuses with absence of the ductus venosus are at risk of other congenital anomalies including facial clefts, hemivertebrae, cardiac, genitourinary, gastrointestinal anomalies; affected infants also have a poorer prognosis. In conclusion, fetuses with features suggestive of absence of ductus venosus require referral to a tertiary perinatal center.