Study links IVF to low intelligence in children
Certain forms of IVF treatment are significantly associated with an increased risk of low intelligence in children, a major study has shown.
A link was also found with an especially severe type of autism, but only in the case of twins or triplets.
Scientists who analysed data on more than 2.5 million births stressed that the chances of an IVF baby being affected remained tiny in real terms.
They found a 51% increased risk of intellectual impairment, marked by an IQ below 70, in children conceived by IVF treatments in which sperm cells are injected directly into eggs.
But the researchers said the result could not be explained by factors such as premature and multiple births and needed further investigation.
The direct injection method, known as Intra-Cytoplasmic Sperm Injection (Icsi), was developed to help infertile men/
In rare cases Icsi treatments are carried out using sperm that is surgically extracted. This procedure led to a more than four-fold increased chance of a child developing a severe and highly disabling form of autism.
The association vanished when multiple births were taken into account, leading scientists to suspect that some factor other than the Icsi procedure was responsible.
The Swedish study, published in the Journal of the American Medical Association, is the first of its kind to compare a wide range of IVF treatments.
Compared with "natural" conception, IVF overall had no effect on autism rates and led to a very small 18% increased risk of low IQ which appeared to be linked to multiple births.
The significant findings only emerged when researchers compared six different types of IVF involving the standard "mixing-in-a-dish" method of fertilising eggs or Icsi.
Icsi used with fresh or frozen embryos produced 51% more intellectually impaired children than standard IVF.
Study leader Dr Avi Reichenberg, from the Institute of Psychiatry at King's College London, said: "Our study shows that treatments developed to manage male infertility are associated with an increased risk for developmental disorders in offspring.
"The exact mechanism is unclear, but there are a number of risk factors, from selection of IVF procedures, to multiple embryos, and to pre-term birth. Whilst intellectual disability or autism remain a rare outcome for IVF, being aware of the increased risk associated with specific types of IVF means offspring at risk can be identified and potentially monitored for developmental disorders, ensuring they receive early detection and appropriate support and care."
The researchers insisted the research should not hinder childless couples seeking IVF treatment.
Co-author Dr Karl-Gosta Nygren, from the Karolinska Institute in Stockholm, said: "There's no question that we would stop any treatment or anything like that because of the findings. On the contrary, the results are reassuring."
He pointed out that the increased risk of birth defects associated with IVF was much higher.
"It's important to remember that the majority of children are born perfectly healthily following IVF," he added. "Our study provides much-needed information for parents and clinicians on the relative risks of modern IVF treatments, enabling them to make the most informed choice possible."
The number of couples seeking IVF treatment has soared in industrial countries in recent years. In 1992, just 0.3% of children born in the UK were conceived through IVF. By 2010 this figure had risen to 2%.