The risk of developing problems by the age of 6 is 2.7 times higher among children born to those with a history of infertility than in those conceived without difficulty, according to US research. The findings offer the strongest evidence that medical obstacles to starting a family can have repercussions for offspring.

Assisted reproduction treatments could have an influence — but the raised risk also applied when a diagnosis of fertility problems was followed by a natural conception. Underlying infertility is therefore more likely to be responsible.

With infertility becoming both more common and more treatable, the research suggests that the incidence of some childhood conditions could rise. One in seven British couples has difficulty conceiving, and 10,242 babies were born through IVF in 2003-04.

Autism is diagnosed ten times more frequently than two decades ago — often because of improved recognition.

Scientists emphasised that the absolute risk to infertile couples of having a baby with a serious disorder remained low.

Mary Croughan, of the University of California, San Francisco, compared children born to 2,000 couples with infertility diagnosed and those born to 2,000 couples who did not have problems conceiving.

After adjusting for the higher maternal age and multiple birth rate in the infertile group, Dr Croughan found that the risk of five disorders — autism, mental retardation, cerebral palsy, seizures and cancer — was 2.7 times higher. The risk for autism alone was four times higher. Moderate developmental problems such as attention deficit hyperactivity disorder, learning disabilities or serious sight or hearing disorders were also 40 per cent more common in this group.

The relative risk was higher for infertile couples who had children after treatment, but this could reflect the greater severity of their problems rather than the treatment itself, Dr Croughan said.

She told the American Society for Reproductive Medicine conference in New Orleans: “We are not finding significant differences between different types of treatment. It seems to be the result of a baseline risk across infertility patients.

“What has caused them to be unable to conceive goes on to cause problems. It is as if a brick wall has stopped you becoming pregnant. Treatment allows you to climb over the wall, but it is still there and it goes on to cause problems.”

She added, however, that more investigation was needed to determine whether treatment created an extra risk.

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