Children born following IVF have no increased risk of autism but may be at a very small increased risk of intellectual disability, a Swedish study suggests. However, the researchers stress that the overall likelihood of children conceived via IVF having an intellectual impairment remains extremely low.
The study, published in the Journal of the American Medical Association, found that the occurrence of intellectual disability was 46.3 per 100,000 births in children born after IVF, compared with 39.8 per 100,000 in those conceived spontaneously - a difference of just 6.5 cases per 100,000 births.
Dr Karl-Gӧsta Nygren from the Karolinska Institutet, a co-author of the paper, said that it confirmed that 'the majority of children are born perfectly healthy following IVF'.
In the study, the largest of its kind, the researchers analysed 2.5 million Swedish birth records from between 1982 and 2007. Of the 2.5 million children, 1.2 percent were born following IVF procedures.
The researchers recorded whether the children had a clinical diagnosis of autism or intellectual disability (defined by an IQ of less than 70, the general population average being 100) at the age of four. For children conceived via IVF the authors also noted whether fresh or frozen embryos were used, whether sperm was ejaculated or surgically extracted, and if intracytoplasmic sperm injection (ICSI) was used. ICSI is an IVF technique that is used in cases of male infertility, and involves injecting a single sperm directly into the egg. (In standard IVF, the egg is fertilised by sperm in a laboratory dish.)
Sven Sandin, a study co-author from King's College London's Institute of Psychiatry, noted that 'when we separated the different IVF treatments, we found that traditional IVF is safe, but that IVF involving ICSI, which is specifically recommended for paternal infertility, is associated with an increased risk of both intellectual disability and autism in children'.
However, when the analysis was restricted to singleton births, this small risk increase disappeared. The authors considered possible explanations for the increased risk of developmental disorders following ICSI, such as parental age and hormonal treatments, but found that these factors could not explain the results. The precise mechanism therefore remains unclear.
Dr Allan Pacey, chair of the British Fertility Society, who was not involved in the study, said that the main message of the research 'is a positive one, suggesting that any risk of these disorders is very low, or absent, in comparison to children conceived naturally'.