IVF babies may be up to nine times more likely to develop a rare genetic disorder that can cause cancer, according to a study.
Scientists say the risks to IVF babies are still tiny
Australian researchers looked at over 1m births between 1983 and 2003, 15,000 of which were conceived using IVF.
According to New Scientist magazine, 37 were born with Beckwith-Wiedemann syndrome (BWS). Four were IVF babies.
The researchers said IVF babies had an increased, but still a tiny risk - just 1 in 4,000 chance - of developing BWS.
Babies affected by BWS are often large at birth. Many are born with abdominal wall defects or kidney problems. They are also at risk of cancerous tumours.
The syndrome is believed to occur because of errors in a process called "imprinting", which happens when the DNA from the 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.
Some scientists believe that IVF may, in some cases, disrupt this imprinting process.
But there is also growing evidence that the sperm or eggs of people with fertility problems are more likely to have mutations or imprinting errors.
These latest findings, which were originally published in the American Journal of Human Genetics, back up similar studies published last year.
Eamon Maher, professor of medical genetics at the University of Birmingham, has also carried out research in this area.
He said couples undergoing IVF should not be overly concerned by these latest findings.
"Every time a child is born there is a small chance of a genetic disorder," he told BBC News Online.
"The prognosis for children who are born with Beckwith-Wiedemann syndrome is also pretty good.
"While children are large in infancy and childhood, this tends to be less of a problem when they grow older."
He added: "While they have an increased risk of tumours early in life, the vast majority go on to have a healthy life."
Those views were echoed by New Scientist magazine.
"There is no need for couples considering IVF to be unduly concerned," it said.
"According to the study, there is only a 1 in 4000 chance of an IVF child having Beckwith-Wiedemann. So the risk is tiny."