Medical Definition of TRAP sequence

  • Medical Author:
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

Reviewed on 9/7/2018

TRAP sequence: Twin-reversed arterial perfusion sequence. TRAP sequence, sometimes referred to as TRAP syndrome, is a condition that occurs only in identical twin pregnancies that share a placenta (known as monochorionic twins). In this condition, one twin is typically healthy, while the other has a serious condition that prevents it from surviving on its own, such as a missing heart (acardiac fetus) or head (anencephaly). This abnormal twin is kept alive because blood is pumped from the normal twin through the placenta, via arteries that pump blood in a 'reversed' direction to the abnormal twin. Because of the extra workload on the healthy twin's heart, the healthy twin is at risk for developing heart failure. TRAP sequence occurs in approximately 1% of monochorionic twin pregnancies and 1 in every 35,000 live births. Also sometimes referred to as acardiac twinning.

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Reviewed on 9/7/2018
Children's Hospital of Philadelphia. "Twin Reversed Arterial Perfusion Sequence (TRAP Sequence)."