Hemophilia carrier: A female carrying a mutant gene for hemophilia on one of her two X chromosomes and a normal allele on her other X chromosome. Hemophilia carriers have concentrations of clotting factor VIII or IX of about 50% of normal and, hence, decreased ability to clot their blood. However, if they have a clinical bleeding tendency, it is usually very mild.
Hemophilia carriers are less likely to die from heart disease than noncarrier women, probably due to their decreased blood clotting which, in turn, makes blockage of their coronary arteries less likely. This is similar to the effect obtained by taking aspirin.