Abnormal fetal cardiovascular morphology Ductus venosus agenesis 2022-04-07T14:12:24Z Agenesis of the ductus venosus A developmental defect characterized by lack of formation of the ductus venosus (a shunt that allows oxygenated blood in the umbilical vein to bypass the liver in the fetal circulation). The ductus venosus (DV) plays an essential role in the fetal circulation because it allows the oxygenated placental blood to bypass the liver and enables preferential flow via the right atrium and foramen ovale to the left atrium. Furthermore, normal umbilical flow via DV is involved in the normal development of the intrahepatic portal venous system. The lack of critical anastomoses between the portal and umbilical venous system and hepatic-systemic venous system results in agenesis of ductus venosus and shunting of umbilical blood through an aberrant vessel. Between 1 in 2532 to 1 in 556 fetuses are affected.