Twin reversed arterial perfusion sequence: a rare entity.

Twin reversed arterial perfusion (TRAP) sequence is an extremely rare complication of monochorionic multi-fetal pregnancy, occurring once in 35,000 births. This condition is characterized by a malformed fetus without a cardiac pump being perfused by a structurally normal (pump) twin via an artery-to-artery anastomosis in a reverse direction. We report a case of a primigravida, who came for routine antenatal checkup to our hospital at 31 weeks gestational age. Ultrasound imaging and magnetic resonance imaging revealed twin monochorionic intrauterine pregnancy with a viable, normal-appearing first twin and amorphous structured second twin connected by umbilical vessels. The patient was monitored with weekly ultrasonography, echocardiography, and Doppler ultrasound examination to ascertain the well-being of the pump twin. She delivered successfully at term a normal live baby and an acardius acephalus fetus. Plain X-ray of the acardius acephalus fetus confirmed the absence of cephalic structures. The perinatal mortality of the pump twin ranges from 35 to 55%; hence, it is essential to diagnose the presence of a pump twin at an early gestational age through improved imaging techniques, so that intervention can be planned early in the pregnancy for a better outcome of the pump twin.