[TRAP (Twin Reversed Arterial Perfusion) Sequence in the Third Trimester]

The twin reversed arterial perfusion (TRAP) sequence is a complex and rare malformation syndrome that can occur in monochorionic twin pregnancies. It is characterized by vascular anastomoses and partial or total malformation of the heart and extremities of one of the fetuses. This leads to a hemodynamic dependence of the "parasitic" fetus (acceptor) from the "pump fetus" (donor). The therapeutic goal is to maximize the survival chances of the pump fetus. Although the optimal time for the therapeutic intervention, using radiofrequency ablation or ultrasound laser coagulation, is not clear yet, it is internationally recommended to be performed before gestational week 16. We present the case of an undiagnosed und therefore unusual monochorionic monoamniotic pregnancy in gestational week 34, in our perinatal center and demonstrate the impressive maximal expression of an untreated TRAP sequence.