Haemophilia is usually inherited. This means that it passes down from one generation of a family to the next in their genes. For females to have severe haemophilia, they must have two copies of the faulty gene – one on the X chromosome inherited from their father and one on the X chromosome inherited from their mother. This is very rare.
More commonly, females have one faulty copy of the gene and one normal copy. They are known as 'carriers' and usually have enough clotting factors from their one normal X chromosome to prevent serious bleeding issues.
When a carrier mother and a father without haemophilia have a daughter, she will have a 50 per cent chance of inheriting the faulty gene from her mother and being a carrier. So if you are a carrier yourself, you will need to ensure that your daughter undergoes testing at some point to determine whether she is also a carrier. If you are thinking about having another child at this stage, you can find more information here.
There is no ‘correct age’ to test a female’s haemophilia carrier status and it really depends on what you and your family feel comfortable with. In some cases, families choose to delay testing, while others prefer to test a child who may be a carrier early on, so that any necessary precautions can be taken. In general, females are usually tested for carrier status some time after they start menstruating, when they are old enough to make an informed decision.
Here are a few things to consider that might help you make your decision:
The Haemophilia Foundation in Australia and New Zealand may also provide you with additional support.
Last reviewed: 23/09/2020
-Haemophilia Foundation Australia
-Haemophilia Foundation of New Zealand