TWIN REVERSED ARTERIAL PERFUSION(TRAP) SEQUENCE- A RARE CASE REPORT

Twin reversed arterial perfusion (TRAP) sequence is a rare malformation (1 in 35,000 live births) that occurs in monochorionic twin pregnancies, resulting in coexistence of a normal pump twin and an acardiac twin. The acardiac twin is dependent upon the normal twin for circulation by means of vascular anastomosis. Arterial system of acardiac twin is perfused in reverse with deoxygenated blood from pump twin. Many of the bizarre defects like absence of cranial vault and facial structures, holoprosencephaly, amelia, diaphragmatic defects, ventral vault defects, absence of heartlungs, single umbilical artery are felt to be caused by low oxygen tension and this causes dramatic alteration in the twin fetal physiology and high perinatal mortality. The acardiac twin is a parasite, putting the pump fetus at risk of high output cardiac failure. Overall only 50 percent of pump twins survive. In our case, a 23years old, Rh positive, gravida two, para one, living one, full term normal delivery ,last child birth- 2years, booked at primary health centre, referred to our institution as a case of twin gestation with discordant growth at 27 weeks of gestation for further management . She came first visit with labour pain, ultrasound showed monochorionic diamniotic twin pregnancy with features suggestive of TRAP sequence and discordant growth.Since unavailability of inutero fetal interventions in our institution, patient was planned for fetal intervention procedure in nearby fetal intervention unit. Patient was started on steroid and tocolytics. Inspite of tocolysis, she progressed to active phase of labour within 5 hours 15 minutes of admission. Following delivery, the pump twin survived for two days with neonatal care and the acardiac twin was stillborn with features of TRAP sequence. The obstetrician and radiologist should be aware of this anomaly especially in twin, multiple pregnancies. so that timely proper measures can be taken to survive the pump twin.