Twin pregnancies

Twin reversed arterial perfusion (TRAP) sequence is the most extreme manifestation of twin-to-twin transfusion syndrome, found in about 1% of MZ twin pregnancies.

• The underlying mechanism is thought to be disruption of normal vascular perfusion and development of the recipient twin due to an umbilical arterial-to-arterial anastomosis with the donor or pump-twin.
• At least 50% of donor twins die due to congestive heart failure or severe preterm delivery, due to polyhydramnios.

Prenatal treatment is by ultrasound guided laser ablation of intrafetal vessels within the acardiac twin.