Two cases of parents claiming the right to choose the genetic makeup of their babies before birth raise serious ethical issues according to a British doctor.

Two cases of parents claiming the right to choose the genetic makeup of their babies before birth raise serious ethical issues according to a British doctor.

Dr Paul Veys, a consultant at London's Great Ormond Street Hospital voiced his fears over the case of an American couple who used genetic screening to give birth to a "genetically designed" baby with the characteristics to provide cells to help his sick older sister.

In the first case of its kind, Adam Nash was born on 29 August to Americans Jack and Lisa Nash to provide a life-saving transplant for his six-year-old sister, Molly, who suffers from a genetic disease.

Doctors at the Illinois Masonic Medical Centre, who performed IVF for the couple, selected from embryos fertilised in the lab the one that did not share Molly's disease and which had been tissue-matched to ensure it was compatible.

A month after Adam was born, blood containing stem cells from his umbilical cord was infused into Molly to treat her inherited condition, called Fanconi anaemia, which leads to failure of bone marrow production. Doctors, who had warned Molly would not survive another year without a transplant, are waiting to see if the transplant has been successful.

Mrs Nash said before the transplant: "We wanted a healthy child. And it doesn't hurt him to save her life."

In a separate case a couple who want the right to choose the sex of their baby are planning to take court action under the newly-adopted European Convention of Human Rights.

Dr Veys said the American case raised serious ethical issues over the future of genetic screening, as creating children to be used as donors for siblings was "wrong".

But he said the case highlighted the "grey area" where genetic screening can save lives and cure fatal diseases but can also offer parents the chance to to choose characteristics like IQ level and eye colour.

Test tube baby Adam Nash was born in Denver, Colorado, on August 29 after being genetically screened as an embryo then implanted in his mother's womb. The embryo was tested to ensure he would be a suitable transplant donor for his six-year-old sister Molly, who suffers from an inherited bone marrow deficiency. Other embryos created by the IVF treatment which were not a match were not implanted.

A month after he was born, life-saving stem cells taken from Adam's umbilical cord were transplanted into Molly and this is thought to be the first time a baby has been "designed" to save the life of another sibling. Molly is said to be doing well and doctors have said she has around a 90% chance of being cured.

Dr Veys said: "This is a very difficult issue and it raises questions about where the cut-off line should be in genetic screening. It is a start towards being able to choose the right coloured eyes and the right intelligence - all you need is the gene and you will be able to do that. It is difficult to know where to draw the line - there is no black and white in this area."

"I believe it is wrong and unethical to have a child as a donor and we discourage parents from doing it. It can raise all kinds of problems - guilt in the second child if they cannot be a donor or the treatment does not work, problems for the parents and the sick child.

"But in this case it might possibly be justified. The parents not only screened their second child to ensure it was healthy but also to ensure it was a match for the older girl who would have died otherwise. The other scenario is that they could have had another child with the same condition or decided on a termination - what is better?"

A spokesman for the Human Fertilisation and Embryology Authority (HFEA) said: "The tests are generally used by couples wishing to avoid passing on a serious genetic condition to their children. Only the licensed clinics can perform the tests and they have to convince a committee of the HFEA that the tests are necessary or desirable.

"If parents wanted to use the screening in the way the US couple have they would have to apply through a licensed clinic to a committee of the HFEA. There may also be an assessment test on the welfare of the child, or in this case, perhaps both children."

Meanwhile Alan and Louise Masterton, of Monifieth near Dundee, are hoping the courts will grant them the right to add a daughter to their family of four sons. They have already suffered the loss of their three-year-old daughter who died in an accident a year ago.

The couple want to use test-tube technology to ensure their next child is a girl despite existing rules which prohibit this without an urgent medical justification.