Fetus diagnosed as Acephalus acardius
"Acephalus is characterized by the absence of the head. Acardius is characterized by the absence of the heart. Usually the upper extremities are also missing. Acephalus is a malformation seen in monozygotic twins' births, where one twin is normal and the other shows extreme deformity. These partial fetuses consist primarily of the pelvis, with the extent of the skeletal development above & below subject to individual variation. The circulation of an acephalic twin is carried through the vessels of the normal twin's placenta."