Morphological and cytogenetic studies on conjoined twins.

Two cases of monoamniotic conjoined male twins, born at term after normal pregnancies, are reported. The first case, a bicephalus, shows hypoplastic and malformed left-side organs, absence of the left umbilical artery, and two communicating hearts, the left one with three cameras. The second case, a pygothoracopagus, consists in a twin "parasite", with no head but with two upper and two lower limbs, slightly less developed than those of the formed twin. The left eye of the formed twin is double than the right one and contains two eye apples -- one well-formed and the other rudimentary. There is a rudiment of a second mouth on the left cheek. The umbilical cord contains five blood vessels --- one umbilical vein and four umbilical arteries. The cytogenetic study of the pygothoracopagus reveals aneuploidy, more pronounced in the "parasite" than in the formed twin.