IVF babies are more likely to suffer from a rare gene disorder and scientists say the finding is another good reason not to make human clones.

Beckwith-Wiedemann syndrome is a condition which causes too much growth, kidney abnormalities and a raised chance of tumours.

The syndrome is the result of errors in a process called "imprinting", which happens when the DNA from mother and father are combined when the embryo is first conceived.

Every embryo is a combination of two sets of genes - one from its mother and one from its father.

It's not unreasonable to think that human cloning would put children at risk of this condition Dr Wolf Reik, Babraham Institute

However, certain genes perform differently, and are more or less active, depending on whether they come from the father or the mother.

This imprinting is a key control which makes sure the foetus develops correctly while it is in the womb.

Scientists believe that fertility techniques such as IVF, and ICSI - in which a single sperm is injected into an egg - may be disrupting this imprinting process.

Although in the vast majority of cases the baby would be healthy, in some cases the problem would have an effect on their future health.

Higher risk

The researchers from the University of Birmingham and the Babraham Institute in Cambridge, both UK, looked at 149 babies diagnosed with the syndrome.

They found that six out of the 149 had been conceived via IVF or ICSI, or 4%.

The proportion of babies born using IVF in the UK is only 1%, meaning that IVF babies are more likely to fall prey to the disorder than those conceived naturally.

Dr Wolf Reik, from the Babraham Institute, said: "The genes themselves are not necessarily any different but imprinting controls how active the gene is.

"If the imprinting goes wrong, control is lost, and this can result in unregulated growth.

"Imprinting is set when the sperm or egg is produced and we believe that IVF and ICSI interfere with the process just after fertilisation, increasing the risk that a child will develop Beckwith-Wiedemann syndrome."

Clone damage

However, he said that the result was bad news for supporters of human reproductive cloning.

There is significant evidence that cloning techniques also interfere with imprinting.

In animal experiments, many foetuses spontaneously miscarry at various stages of pregnancy, and scientists are still not sure why, although miscarriage is often a safety mechanism that halts a foetus which is not developing correctly.

Dr Reik said: "Evidence is emerging that imprinting is also faulty in cloned animals so it's not unreasonable to think that human cloning would put children at risk of this condition and others like it."

Sir Paul Nurse, the chief executive of Cancer Research UK, said: "Cancer Research UK is opposed to reproductive cloning and this research highlights just one of the severe problems that may result."