Prenatal diagnosis by linkage: hemophilia A and polymorphic glucose-6-phosphate deydrogenase.

Close linkage between the loci for G6PD and hemophilia A allows prenatal diagnosis of hemophilia in the fetuses of certain women who are heterozygous for two electrophoretic types of G6PD. A pregnant woman, whose mother was an obligate heterozygote for hemophilia, had factor VIII levels and a G6PD phenotype that failed to indicate clearly whether or not she was heterozygous for hemophilia. The G6PD phenotype of her male fetus revealed that the fetus was unlikely to have hemophilia.