Hemophilia Inheritance: Risks for Sons and Daughters of Affected Males and Carrier Females

Hemophilia A/B are X-linked recessive disorders. Inheritance patterns differ by parental status:

Father with Hemophilia (Affected Male)

• All daughters receive his affected X chromosome → obligate carriers.
• All sons receive his Y chromosome → unaffected (unless mother is a carrier).

Mother Who Is a Carrier

• Each pregnancy: 50% chance to pass affected X.
• Sons: 50% chance of hemophilia.
• Daughters: 50% chance of being carriers.

Carrier Female × Affected Male

• All sons: Father gives Y; mother gives affected X 50% → 50% affected.
• All daughters: Father gives affected X; mother gives affected X 50% → 50% affected (homozygous), 50% carriers. Homozygous females are rare but can have severe symptoms.

Risk Reduction

• Genetic Counseling: Preconception or prenatal.
• Prenatal Diagnosis: CVS (10–13 weeks), amniocentesis (15–20 weeks) for known familial mutation.
• Preimplantation Genetic Testing (PGT-M): With IVF, select unaffected embryos.

Carrier females may have mild bleeding symptoms (factor levels 30–60%); factor assays and genetic testing confirm status.