Twin-reversed arterial perfusion sequence

Definition

A rare disorder related to monochorionic twin pregnancy characterized by complete or partial absence of cardiac development in one twin (''acardiac twin'') and blood supply of both circulations by the morphologically normal co-twin (''pump twin'') via an arterioarterial anastomosis. In most cases, the acardiac twin has well developed legs and pelvis but no cephalic pole, thoracic organs, and upper extremities. The condition is associated with a high risk of perinatal death of the pump twin due to a combination of high-output cardiac failure and polyhydramnios-related pre-term birth. Hypoxia and intrauterine growth restriction are also seen in the pump twin.