There are two types of carriers: obligate carriers and possible carriers. Obligate carriers necessarily have the hemophilia gene, which they inherit from their father. Obligate carriers can be identified by getting a detailed family history (known as a pedigree).
Obligate carriers are:
- All daughters of a father with hemophilia;
- Mothers of one son with hemophilia and who have at least one other family member with hemophilia (a brother, maternal grandfather, uncle, nephew, or cousin);
- Mothers of one son with hemophilia and who have a family member who is a known carrier of the hemophilia gene (a mother, sister, maternal grandmother, aunt, niece, or cousin)
- Mothers of two or more sons with hemophilia.
Possible carriers are:
Many carriers, even obligate carriers, are unaware of their status
- All daughters of a carrier
- Mothers of one son with hemophilia but who do not have any other family members who have hemophilia (or are carriers)
- Sisters, mothers, maternal grandmothers, aunts, nieces, and female cousins of carriers.
