A case of TRAP sequence: acardiac twin.

Monochorionic twinning contributes significantly to neonatal morbidity and mortality. The twin-twin transfusion syndrome complicates 5-35% of monozygotic twin pregnancies with monochorionic placentation. The most severe and a rare manifestation of this condition is acardiac twinning which is seen in 1 in 35,000 pregnancies. The acronym TRAP (Twin Reversed Arterial Perfusion) sequence is used to describe this condition. The acardiac twin does not survive while the mortality for the normal twin is about 50%. Proper timing of the delivery is of prime importance to survival of the normal fetus for which emphasis is placed on close sonographic monitoring for early antenatal diagnosis. We present such a case of TRAP sequence because of its rarity.