IVF techniques that, if approved by Parliament, would for the first time permit the transfer of genetically modified embryos into the womb are the subject of a new consultation by the Human Fertilisation and Embryology Authority (HFEA).

The techniques have been developed to enable women who suffer from a form of mitochondrial disease, caused by faults in the DNA of mitochondria (often described as the human cell's batteries), from passing it on to their children.

IVF is used to fertilise a mother's egg, containing "unhealthy" mitochondria, with the father's sperm. The nucleus of the fertilised egg is then collected and transplanted into a donor egg containing healthy mitochondria, but with its own nucleus removed.

More than 99 per cent of the child's genes would come from the mother and father, while less than one per cent would be inherited from the donor. This change would affect the germ line, meaning that the donor's mitochondrial DNA would be passed on to future generations. Germ-line modifications have never been permitted on embyros before.

A change in the law is required for clinical trials to begin. The Government has asked the HFEA to "take the public temperature".

The website for the consultation (which is open until 7 December) outlines issues that the proposals raise, including concerns that they could constitute "the first step on a slippery slope to genetic modification, perhaps for trivial purposes", and questions about the impact of inheriting DNA from three people on a child's sense of identity, and society's concepts of parenthood. It also notes that, even if the techniques were legalised, they would remain experimental, and the impact would not be fully known until after the children were born.

An ethical review published by the Nuffield Council on Bioethics in June concluded that, if the techniques were "adequately proven to be acceptably safe and effective", it would be "ethical" for families to use them, owing to "the health and social benefits" of freedom from mitochondrial disorders, and where potential parents prefer to have genetically related children.

The review discusses the significance of the proposal to legalise an alteration to the germ line. The UN's Universal Declaration on Human Genome and Human Rights describes the human genome as "the heritage of humanity", and gives the International Bioethics Committee a duty to identify "practices that could be contrary to human dignity, such as germ-line interventions".

The director of Human Genetics Alert, Dr David King, said that the techniques "set a precedent for allowing the creation of genetically modified babies", and he questioned their safety. "Bioethicists and governments have long insisted that modification of the human germ line be banned, because it could allow a new and extremely dangerous form of eugenics."

The Christian Medical Fellowship called the techniques "unnecessary, unethical, and overhyped". It argues that alternatives such as adoption and egg donation are already available.

The director of research at the Muscular Dystrophy Campaign, a charity that funds research into the techniques, Dr Marita Pohlschmidt, said: "For women who have been dealt the heavy blow of living with mitochondrial disease, the prospect of bearing healthy children is of immeasurable value. . . It is only through communicating the reality of this complex procedure - and the issues and questions it presents - that reservations can be dispelled."

The HFEA states that about one child in 200 is born each year with a form of mitochondrial disease. But the Nuffield report notes that most cases are mild or asymptomatic. About one in 6500 is estimated to develop a more serious, even fatal, mitochondrial disorder.

http://mitochondria.hfea.gov.uk/mitochondria/