[Prenatal diagnosis of hemophilia B].

The authors are reporting on the prenatal diagnosis of the X-linked haemophilia B for the first time in Hungary applying the polymerase chain reaction. DNA sequence containing a HhaI restriction endonuclease site close to the factor IX gene was amplified using polymerase chain reaction. The products from polymerase chain reaction were detected on polyacrylamide gel with ethidium bromide staining after the digestion with HhaI restriction enzyme. In the first step of the diagnosis DNA specimen was prepared from chorion derived from a 11th week gestation of haemophilia B carrier mother. The investigation of fetal DNA proved a male fetus. The detection of HhaI polymorphism of the fetus demonstrated the inheritance of the disease causing allele. The parents asked for the termination of pregnancy based on the result.