Oral contraception and the detection of carriers in haemophilia B

In a study of 40 normal women and 37 obligatory carriers from 14 haemophilia B families, we tried to establish whether age or the use of oral contraceptives exert an influence on carrier detection. Age has no influence on the levels of factor IX activity and antigen in the group of carriers. The use of oral contraceptives has a definite influence on factor IX activity and antigen. The average factor IX activity level in the normal women without the pill, was 92% against 121% in the group who used the pill. A similar difference was found in the levels of factor IX antigen. As to the 37 carriers, we also found significantly higher levels in the group using oral contraceptives than in the other group. This finding is important for future carrier detection programs. As a reference one should consider the values found in normal women and obligatory carriers, subdividing each group in those using the pill and those who do not.