Britain's first genetic "designer" baby has been born to a couple who are desperate to cure their young son who has a rare form of anaemia.
Jamie Whitaker was delivered by Caesarean section on Monday after being genetically matched, while still an IVF embryo, to his four-year-old brother Charlie.
Charlie has the rare Diamond Blackfan anaemia which only a transplant of stem cells from a sibling with a perfect match can cure.
His parents, Jayson and Michelle, travelled to the Reproductive Genetics Institute in Chicago for the specialised treatment after being refused permission to genetically select a tissue match embryo by the Human Fertilisation and Embryology Authority.
Mr Whittaker, 33, a business manager who has recently moved his family from Bicester, Oxfordshire to a Derbyshire village, was aware of the controversy surrounding the issue of so-called designer babies but said: "All we did was change the odds from a one-in-four chance of a tissue match to a 98 per cent chance.
"There was no selection on the basis of colour of eyes or hair or sex."
He added: "There are blood tests being carried out now to see if Jamie is a perfect tissue match and we will know in a few days but, at the moment, we don't want to think about the stem cell blood."
The vital stem cells have already been collected from Jamie's umbilical cord and a series of tests will also be carried out to determine if the new baby has the same anaemia condition as his brother.
Liberal Democrat health spokesman Evan Harris, the Whitakers' MP until their move recent move to Derbyshire, said the Government should allow Parliament to re–examine the law on fertility.
"It is high time that the Government allowed proper public and parliamentary debate and amendment to the Human Fertility and Embryology Act to permit this sort of treatment.
"The Act is 13 years old and is no longer up–to–date with clinical developments."
Dr Lana Rechitsky, of the Chicago Reproductive Genetics Institute, where Jamie's embryo was selected and implanted, denied the fertility treatment was unethical.
She told BBC Radio 4's Today programme: "The main thing people say we are doing wrong is they say we are making designer babies. That is wrong.
"These are not babies brought into the world just to save the sibling's life. These are families who want a healthy child, and if that healthy child can also save the life of the child they already have, I think it is a double blessing.
"There was no other way for Charlie to survive."
Sheffield Teaching Hospitals NHS Trust confirmed that the parents had undergone treatment and that Jamie was born in Jessop Wing maternity unit.
A statement said: "Michelle and Jayson Whitaker became the proud parents of a baby boy following PGD/IVF treatment in order to produce an embryo with the same tissue type as their young son Charlie."
The HFEA said the case differed from that of Raj and Shahana Hashmi, who were given permission for IVF treatment to help cure their four–year–old son, Zain, who is seriously ill with a rare genetic blood disorder.
"The Hashmis' case was genetic so they can screen future embryos to check that they do not have the disease – and at the same time find out if there is a tissue match," the spokeswoman said.