Case history

Helen Cross's 4 year old son has just had Duchenne's muscular dystrophy diagnosed. Genetic testing confirms the diagnosis and shows that she is a carrier for the mutation. Mrs Cross's sister, Penelope Yates, is 10 weeks pregnant. Mrs Yates's obstetrician referred her to the genetics team after she told him that her nephew had speech and development delay. She told him that although she was not close to her sister and had not discussed it with her, she was concerned about the implications for her own pregnancy. In her discussions with the clinical geneticist (who did not know at this stage that both sisters were patients in the same clinic) Mrs Yates made it clear that she would consider terminating a pregnancy if she knew that the fetus was affected with a serious inherited condition.

Speech and development delay are features of several conditions and would not of themselves indicate carrier testing for Duchenne's muscular dystrophy. In addition, because the Duchenne gene is large and several possible mutations exist, testing without information about which mutation is responsible for the nephew's condition is unlikely to be informative.

At her next meeting with her clinical geneticist, Mrs Cross says that she knows that her sister is pregnant and that she understands that her sister's baby could be affected. She says that she has not discussed this with her sister, partly because they don't really get on but also because she suspects that if her sister were to find out, and if the fetus turned out to be affected, she would terminate the pregnancy. Mrs Cross …