Twin Reversed Arterial Perfusion Sequence Malformation

**Semantic type:** Congenital Abnormality

**Definition:** A severe form of twin-twin transfusion syndrome that occurs in monochorionic pregnancies. The normal twin (pump twin) supplies the blood flow to its sibling that lacks heart or brain or both (acardiac/acephalic twin). Untreated, it may lead to the demise of the pump twin in some cases.

**Synonyms:** - Acardiac Malformation - Acardiac Malformation - Acardiac Twin - Acardiac Twin - TRAP Sequence - TRAP Sequence