Michelle Whitaker gave birth to a son, Jamie, by Caesarean section at the Royal Hallamshire Hospital in Sheffield, northern England, on Monday.
Jamie was conceived through in vitro fertilization and genetically matched, while still an embryo, to his 4-year-old brother Charlie. Charlie suffers from Diamond Blackfan Anemia, an extremely rare condition that requires regular blood transfusions. He needs a bone marrow transplant, and his parents were hoping to produce a sibling whose tissue type matched.
The idea is to use umbilical cord blood from the new baby to treat his brother. The umbilical cord contains bone marrow stem cells — immature cells that later develop into bone marrow.
The Whitakers sought permission from Britain's Human Fertilization and Embryology Authority to use in vitro fertilization to create and select an embryo that would be a match for Charlie. When permission was denied in August, they had treatment at the Reproductive Genetics Institute in Chicago.
Critics worry that such selection could lead to babies being created to provide spare parts, and about "the ill effects that there may be on a child, on an embryo going through these treatments, and also the social and emotional effect of being a child created, if you like, to save a sibling," said Angela McNab, chief executive officer of the Authority.
But Charlie's father, Jayson Whitaker, was quoted by a British newspaper as saying "there was no selection on the basis of color of eyes or hair or sex.
"All we did was change the odds from a one-in-four chance of a tissue match (from a baby conceived naturally) to a 98 percent chance," The Daily Mail quoted him as saying.
During in vitro fertilization, several embryos are created but only two or three are implanted in the womb. Genetic tests are normally done when one or both parents carry an inherited disorder, to let doctors be sure the embryo they implant does not have the disease-causing genes.
In December 2001, the fertilization authority announced that it would, in principle, permit couples to select test-tube embryos whose tissue type matches that of a sick sibling, if the couple already qualified for embryo testing to avoid passing on an inherited disease.
Last year the authority gave another couple, Shahana and Raj Hashmi, permission to test to make sure tissue from their next child would be a suitable match for their ailing 2-year-old son, Zain, who suffers from the rare blood disorder thalassaemia and is expected to die without a transplant.
In that case, the boy's illness was hereditary. Screening the new baby would be necessary anyway to ensure the new child did not have the disease genes.
But Charlie Whitaker's condition is not usually inherited, and there is only a one-in-50 chance that the couple's next child would have the disease. Since neither parent carried the genetic mutation, the regulator concluded, it could not be argued that genetic screening of the embryo was necessary to select ones free from the condition.
Cases of embryo selection for matching tissue for sick siblings have occurred in the United States, where private fertility clinics are unregulated.
Dr. Lana Rechitsky, a doctor at the Chicago institute that treated the Whitakers, said the procedure did not amount to creating "designer babies."
"We are not creating anything new. We are just trying to choose between the embryos to find the one that is normal and can save the life of its sibling," she told British Broadcasting Corp. radio.
But Suzi Leather, chairwoman of the Human Fertilization and Embryology Authority, advised caution.
"This is an area of considerable legal and ethical uncertainty, and we currently don't think it's right that just because we can do something, we should immediately start doing it," she told the BBC.
"What this involves as a technique is removing one or two cells (from the embryo) and testing them. We don't know what the long-term consequences of that will be for the child being created.
"It seems to me that in this area of considerable uncertainty, where there is a possibility of theoretical risk, that we should adopt a precautionary approach," she added.
The Human Fertilization and Embryology Authority, the only regulator of its kind in the world, keeps tight control in Britain over the practices of all fertility clinics and over embryo research.