Prenatal Diagnosis: Heredity Disorders, Other Biochemical Diseases, and Disfiguring Birth Defects There are over 250 recognized sex-linked diseases, affecting every organ system. Of these, 95% affect males, (Emery, 1968). Despite these many sex- linked diseases, at present prenatal diagnosis can specifically be made in fewer than 40 diseases. (Emery, 1968). These sex-linked diseases are individual rare and some are named after physicians who described them, for example, Hemophilia A and B, Duchenne muscular dystrophy, fragile-X syndrome, Fabry disease,