Twin reversed arterial perfusion sequence in a monochorionic monoamniotic twin pregnancy: a very rare condition

Twin reversed arterial perfusion sequence (TRAP) is a very rare congenital anomaly. We present sonographic findings of TRAP sequence in the case of a multiparous woman with a monochorionic monoamniotic twin pregnancy who was referred to our unit for blood sugar control. The patient had a history of co-twin demise at 13 weeks of gestation without appropriate fetal surveillance afterwards. We found a monochorionic placentation with a normal appearing pump twin, an abnormal appearing co-twin without obvious cardiac activity and reversed arterial flow toward instead of away from the anomalous acardiac fetus. Therefore, the sonographic diagnosis of TRAP sequence was confirmed. We recommend considering the potential rare complications of monochorionic twin pregnancy which necessitates proper surveillance and intervention to monitor suitable growth of pump twin.