Couples with fertility problems are three times more likely to have a child with serious conditions like autism and cerebral palsy, research suggests.
The work compared couples who did and did not seek fertility treatment
The extra risk is likely to be caused by health problems that make it difficult for these couples to conceive in the first place, scientists believe.
Fertility treatments, such as IVF, may contribute too, an American Society for Reproductive Medicine meeting heard.
But the experts stressed the overall risk was still relatively low.
They said couples should be counselled about the risks and encouraged to improve their health before undergoing fertility treatment.
Professor Mary Croughan, who led the University of California research on 4,000 women and their children aged up to six years, explained those with fertility problems were also more likely to have other health problems, such as heart disease and diabetes, and were more at risk of pregnancy and labour complications.
She said: "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."
Her team found the risk of five conditions - autism, mental retardation, cerebral palsy, seizures and cancer - was 2.7 times higher among the children born to 2,000 women who experienced fertility problems than among those born to the 2,000 women who did not have difficult conceiving.
For autism alone, the risk was four times higher.
Moderate developmental problems such as attention deficit hyperactivity disorder, learning disabilities or serious sight or hearing disorders were also 40% more common in the children born to the couples who struggled to start a family.
Stuart Lavery, a spokesman for the British Fertility Society, questioned how valid the findings were because of the wide range of fertility problems and treatments the women had.
"There is no doubt that people who have difficulties with their fertility have difficulties conceiving and carrying pregnancies, although it has not been shown that it is the infertility that is causing the problems," he added.
Clare Brown of Infertility Network UK said continued work was needed to ensure treatment was safe for couples and potential children.
At the same conference, doctors heard how Britain should consider paying women thousands of pounds to donate their eggs.
US clinics often pay women up to $10,000 (£5,200) per IVF cycle. In comparison, British clinics can offer £250 plus travel and childcare expenses.
A spokesman for The Human Fertilisation and Embryology Authority said it had no plans to review the £250 cap, set last year.