Factor IX levels during pregnancy in a women with hemophilia B.

The levels of factors VIII, II, and VII rise during pregnancy in normal women. In addition, increases in factor VIII levels have been observed in pregnant carriers of hemophilia A and in women affected with von Willebrand's disease. The influence of pregnancy on factor IX levels is less clear. Consequently, we determined serial factor IX coagulant activities (IX:C) and factor IX antigen levels (IX:Ag) during the pregnancy of an affected carrier of hemophilia B who had baseline values of 13% both IX:C and IX:Ag levels. Neither level rose during pregnancy and the patient was treated with plasmapheresis and plasma infusions during the delivery and the postpartum period. Excessive bleeding did not occur.