A British couple have won the right to test embryos for a gene that leads to high cholesterol levels and an increased risk of heart attacks, The Times has learnt.

The decision by the fertility watchdog will reopen controversy over the ethics of designer babies, as it allows doctors to screen embryos for a condition that is treatable with drugs and can be influenced by lifestyle as well as genes.

While the procedure is designed to detect a rare version of a disease called familial hypercholesterolaemia (FH), which often kills children before puberty, it will also identify a milder form that can be controlled by drugs and diet.

Critics argue that the test will allow couples to destroy embryos that would have had a good chance of becoming children with fulfilling and reasonably healthy lives.

The test will also create an unprecedented moral dilemma for some couples, as it could show that they have produced no embryos completely unaffected by the disease. This would force them to decide whether to implant embryos that they know have a genetic risk of premature heart disease and death, or to throw them away and deny them a chance of life.

Britain’s first licence to test embryos for FH will be awarded next week to Paul Serhal, of University College Hospital in London, by the Human Fertilisation and Embryology Authority (HFEA).

Its decision breaks new ground because it permits Mr Serhal to screen out not only the severe form of the condition but also the milder type, which is usually treatable.

Embryo screening has previously been approved only for disorders in which a gene invariably causes a serious disease, or for conditions such as breast cancer in which mutations carry an 80 per cent lifetime risk.

FH occurs in two forms. The more common version, heterozygous FH, affects 1 in 500 people. It is caused by a single mutated gene, which raises cholesterol and thus the risk of hardened arteries, heart disease and stroke. It can usually be managed with statin drugs and diet.

One in 250,000 people inherits two defective copies of the gene and develops homozygous FH, which is much more serious. Sufferers show severely elevated cholesterol from the age of 5, and can suffer angina by 6 or 7. Many die in childhood, and most have suffered at least one heart attack by the end of their twenties.

Mr Serhal’s patients, who are in their thirties, both have the milder heterozygous FH. They discovered their status only when they had a daughter, now 5, with the homozygous form, and they also have an unaffected son.

They said yesterday that they were delighted. “We had no idea that we both carried a gene for high cholesterol until the double gene was expressed in our first child. We are very lucky that our child has responded so well to the very high-dose drug regime. We have been led to understand that other children with the same double gene may not be so lucky.”

The couple, who approached Mr Serhal after learning that he was offering the pre-implantation genetic diagnosis test for a breast cancer gene, will have IVF next month, even though they are naturally fertile.

A single cell will be removed from each embryo at the eight-cell stage, and be tested for defective FH genes. Any that have homozygous FH will be discarded. The test will also determine whether the remaining embryos are completely clear of FH, or whether they have the heterozygous form. There may be none that are unaffected, leaving the couple with a difficult ethical decision.

Mr Serhal said: “This obnoxious disease can cause cardiovascular accidents at a very young age. Ideally, we will find embryos with no FH genes, but it is possible we will not and it will be up to the patients to choose. Some people would think twice about using embryos that they know have a risky gene, and others would say you shouldn’t screen out a condition that can be managed so people can live with it. It will be an awkward choice.”

Mr Serhal said that the HFEA had also indicated that it would be prepared to sanction screening for the milder form of FH alone for couples in which one partner was a carrier and the other was not, though he was not yet proposing to do such screening.

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