A pregnancy was terminated at 24 weeks of amenorrhea when tetraploidy (92 XXXX) was diagnosed in fetal blood subsequent to ultrasonographic detection of a polymalformation syndrome. The severity of the neurological deficit in tetra-ploid infants and their death befor 2 years of age require that prenatal diagnosis by cordocentesis be performed for analysis of fetal blood in cases of equivocal and nonspecific polymalformation syndrome and justify that medically-induced termination of pregnancy is suggested in the event of intrauterine tetraploidy diagnosis.