Haemophilia

Haemophilia is an inherited bleeding disorder caused by a deficiency of a specific blood clotting factor, most commonly factor VIII (haemophilia A) or factor IX (haemophilia B). It is usually inherited in an X-linked pattern, meaning the affected gene is on the X chromosome; this means haemophilia most often affects males, while females who carry one altered copy are usually unaffected carriers but can pass the condition to sons. Families with a known history of haemophilia may be offered genetic counselling to understand carrier status and reproductive options, which can include prenatal testing in a pregnancy or, in some situations, PGT-M during IVF to test embryos for the familial variant. A carrier diagnosis affects reproductive planning but does not itself cause symptoms in most female carriers, though some can have mildly reduced clotting factor levels worth discussing with a haematologist.

Also known as: haemophilia A, haemophilia B, hemophilia

Last reviewed: 9 September 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.