BACKGROUND Monochorial twin pregnancies are characterised by the presence of vascular connections between the twins. These connections can be the cause of pathologies such as the twin-twin transfusion syndrome or the TRAP syndrome, which is defined as the association of a headless, acardiac twin with a healthy twin. METHODS The case of an acardiac, headless twin diagnosed during pregnancy at 24 weeks of amenorrhea is described. CONCLUSIONS An acardiac headless twin is a rare phenomenon. Yet early diagnosis is crucial during pregnancy to provide adequate monitoring. It is associated with a high death rate in the healthy twin caused by anaemia and heart failure. Therapeutic resources involve interruption of vascular anostomoses between the twins in order to perform a selective feticide. CONCLUSIONS Treatment of acardiac headless twin pregnancy ranges from obstetric abstentionism to interventionism, which depends on the prognosis for the healthy twin, dominated by the risk of preterm birth and heart failure.