IVF could double the risk of cerebral palsy, according to a study of more than 90,000 children.
Several studies have shown that rates of the neurological condition, which can result in speech problems, muscular stiffness and curvature of the spine, are higher in couples who have undergone in vitro fertilisation (IVF).
But this is the first to suggest that the process of IVF itself could increase the risk, rather than it being a consequence of the parents' impaired fertility
Researchers at the University of Aarhus in Denmark found that babies born by IVF were more than twice as likely to have cerebral palsy as those conceived naturally.
The result held up even after adjusting for factors like the age of the mother, if she smoked, and whether the baby was premature or a twin.
Dr Jin Lieang Zhu, an epidemiologist, and his team concluded that IVF was probably the underlying cause by looking at how rates of cerebral palsy changed depending on how long it took the mother to conceive naturally. This is considered a good measure of underlying fertility.
They found no statistically significant difference in rates between those whose mothers took less than two months to conceive, and those who took more than a year.
However, there was a much bigger difference between those who took over a year to conceive and those who only got pregnant thanks to IVF.
Even though this difference was not statistically significant, probably due to the small number of cases of cerebral palsy, the researchers concluded that IVF "confers a risk of cerebral palsy".
Dr Zhu stressed that the overall risk of having a child with cerebral palsy was still low.
About one in 176 children born via IVF in the study had the condition, compared to the British average of about one in 400.
He also said modern IVF techniques, such as only transferring one embryo to the womb, could eliminate the heightened risk altogether.
The study is published today in the journal Human Reproduction
Article 3rd November 2010 www.telegraph.co.uk
Read more about IVF and alternatives to IVF