Öz
TRAP sequence (twin reversed arterial perfusion) is a complication with a poor prognosis, seen only in monochorionic twin pregnancies, known as acardiac twin formation1. In the very early stages of the formation periods of twin pregnancies, as a result of the single formation of the placenta and the defective formation of the cord vessels of the second baby (acardiac twin), the heart and accordingly the brain development cannot occur in the baby with placenta abnormalities; but other parts of the body can develop in different combinations. Therefore, the second baby can develop from a separate creature to the other baby as a parasite. The normal twin, is known as the pump twin and provides the blood circulation of the acardiac twin. These inter twin anastomoses lead to circulatory confusion, the reverse circulatory morphogenesis interrupted and acardiac twinning occurs2. This case is presented because the patient had a healthy twin who was born due to the onset of preterm labor that was not terminated at the request of the family, and the other twin with acardiac anencephaly. Ablation treatment could not be performed due to the delay in our case, and the pump twin was delivered in a healthy way.