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Haemophilia A – carrier mother risk — RACP Paediatrics MCQ

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EasyGeneticsHaemophilia A – carrier mother riskRACP Paediatrics

A mother is a known carrier of haemophilia A (F8 mutation). She is pregnant and wishes to know the risk for her unborn son. What is the probability that the son will be affected?

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Correct answer: B — X-linked recessive – carrier mother

Haemophilia A is X-linked recessive. A carrier mother has a 50% chance of passing the affected X chromosome to each son. Sons who inherit the mutation will be affected (haemophilia A); daughters who inherit it will be carriers. Prenatal testing or preimplantation genetic testing can determine the fetal F8 genotype.

Reference: RACP Paediatric Curriculum – Genetics; RCH Melbourne – 2023