Twin Reversed Arterial Perfusion

Twin reversed arterial perfusion (TRAP) sequence is a rare condition found only in monochorionic pregnancies. It is a sequence in which a severely anomalous twin with an absent or rudimentary heart, also called an “acardiac twin,” is perfused by its co-twin. The cardiac system of this co-twin (pump twin) provides circulatory support to the acardiac twin from as early as the first trimester. The exact pathogenesis of TRAP sequence is still unknown. However, the mere presence of vascular anastomoses in the placenta alone cannot lead to the development of TRAP sequence. Moreover, the presence of retrograde blood flow through arterio-arterial anastomoses increases the possibility of TRAP sequence diagnosis in a suspected monochorionic twin pregnancy. This report presents a case of TRAP sequence, which was undiagnosed till the delivery of twins. A 26-year-old patient gravida 3 para 2 (G3P2+0) with previous two normal deliveries, was referred to our emergency labor room at (assumed) 37 weeks of pregnancy, from a primary health center with complaints of vaginal leakage and a non-reassuring fetal status. She was immediately shifted to Operation Theatre and an emergency lower-segment cesarean section was performed. At the time of delivery, she was diagnosed as having a monochorionic diamniotic twin with TRAP sequence as one of the twins was acardiac, while the other was a live male baby (the pump twin) with massive ascites. A TRAP sequence pregnancy with a poor prognostic factor requires twin cord occlusion therapy or another form of intervention. Termination of the pregnancy is also an option, as it saves the patient from unnecessary obstetrical complications and morbidity.