A landmark legal ruling allowing a couple to "select" a baby to help cure their existing son will not herald a genetic free-for-all, say judges.
Zain Hashmi is seriously ill
The Court of Appeal said that every case of its type in the future would have to be assessed on its own merits, regardless of the decision in favour of Shahani and Raj Hashmi, from Leeds.
Their son Zain, four, has beta-thalassaemia, which could be cured by a bone marrow transplant.
In the absence of a donor, the couple wanted to have IVF - but use only embryos which were a genetic match for Zain.
The umbilical cord of the resulting baby would contain cells that could be transplanted into Zain.
The Human Fertilisation and Embryology Authority, which regulates IVF in the UK, originally agreed to the procedure, called "embryo selection", to take place.
However, a pro-life group, Comment on Reproductive Ethics (Core), challenged that decision at the High Court and won, forcing the Hashmis to seek treatment abroad.
Core claimed that the HFEA approval amounted to a licence to "create children for spare parts", and said the authority had exceeded its powers.
The High Court ruling was overturned at appeal earlier this year, and on Friday gave its full reasons for this.
Lord Justice Schiemann confirmed that the decision did not automatically give permission for other couples to select genetic traits for their children.
He said: "If the decision of the authority is upheld in the present case it does not mean that parents have a right to in vitro fertilisation for social selection purposes."
Parliament did not sanction a "free-for-all", he said.
The HFEA's original ruling stipulated that it would have to consider all cases of "embryo selection" on their individual merits.
The body has rejected claims that the Hashmi decision could allow "designer babies" to be created in UK clinics.