The infrahepatic IVC develops from three paired embryonic veins at around 6-8 weeks of embryogenesis:
Absence of the entire IVC would result from failure of all three embryonic veins to develop properly.
Absence of the infrarenal IVC would be the result of failure of the posterior cardinal and supracardinal veins to develop.
Controversy exists as to whether these conditions are the result of true anomalies or perinatal IVC thrombosis. Patients usually present with multiple DVTs, often at a young age.