Even if there was, there is thought to be only a one in 50 chance of the Whittakers having another child with the illness, so they would not be good candidates for this type of "pre-implantation genetic diagnosis".

BBC: Q&A: 'Designer baby' refusal

As a bonus, existing techniques, such as pre-implantation diagnosis, will allow couples to select embryos free of a growing number of diseases whose genetic basis is known, and which could be detected through laboratory testing prior to being implanted in a cosy womb.

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