What is Twin Reversed Arterial Perfusion Sequence (TRAP)?
With Twin Reversed Arterial Perfusion Sequence (TRAP), one twin, lacking a functioning cardiac system, receives blood from the normally developing twin called the “pump twin.” This places an enormous demand on the heart, essentially representing a “parasite” tissue mass, putting the pump twin at risk for cardiac failure. Left untreated, the pump twin will die in 50 to 75 percent of cases. The risk to the pump twin rises proportionately to the increasing size of the abnormally developing twin. Twin Reversed Arterial Perfusion Sequence (TRAP) is also associated with excess amniotic fluid, which may lead to premature rupture of the fetal membranes and preterm labor. “Reversed arterial perfusion” is used to describe this condition because blood enters the abnormal twin through the umbilical artery (which usually carries blood away from the fetus back to the placenta) and exits through the umbilical vein, which normally carries blood from the placenta to the fetus.
