When a familial mutation has already been identified in the FVIII or FIX gene, a prenatal diagnosis can be made by either chorionic villus sampling or amniocentesis. Outside of the prenatal context, mutation testing in hemophilia can be used for carrier detection for family planning purpose and as one component of the risk analysis for inhibitor development. In hemophilia A and B. large gene deletions are associated with a higher risk of inhibitor formation soon after exposure to clotting factor therapy, and in hemophilia B, there is also the risk of anaphylactic reactions in these patients. Determination of the hemophilic genotype is now regarded as the standard of care in comprehensive hemophilia treatment centers (see box on Hemophilia Carrier Detection and Prenatal Diagnosis).