[Case report of a twin-monster, dicephalus, dibrachius (author's transl)].

The dicephalus dibrachius twin malformation is a rare developmental anomaly. Spontaeous birth is impossible. Prenatal diagnosis of this condition is difficult though essential to prevent danger to the life of the mother. Radiological examination before birth is necessary. Auscultation and bimanual examination only may lead to the erroneous diagnosis of a twin pregnancy, as in this case, where in the end a cesarean sectionwas performed because unseparated twins were suspected.