Researchers in Sweden have found evidence to suggest that in-vitro fertilization (IVF) treatment is associated with a small increased risk of mental retardation.

The authors said that there was no association found with autistic spectrum disorders, and stressed that the risk of mental retardation identified was only minimal. They published their findings in the July 3 issue of JAMA.

Over 2.5 million children born in Sweden were included in the study. The team set out to determine whether the rate of mental retardation among test-tube babies was higher than among other babies.

As background information, the authors informed that there have been around 5 million infants born from IVF since 1978.

Yet, “no study has investigated the association between different IVF procedures and neurodevelopment, and few studies have investigated whether IVF treatments are associated with neurodevelopment after the first year of life. Few studies have looked at autism spectrum disodrders and mental retardation, 2 of the most severe chronic developmental disorders, affecting 1 percent to 3 percent of all children in developed countries.”

Team leader, Sven Sandin, M.Sc., of King’s College London, and colleagues analyzed the risk of autism spectrum disorders (ASD) and mental retardation in children born from IVF and different IVF procedures.

Children born between 1982 and 2007 were tracked for any diagnosis of ASD or mental retardation until 2009. The team used data from the Swedish National Health Registers.

The investigators also determined whether the IVF treatment involved intracytoplasmic sperm injection (ICSI), and whether the embryos selected were fresh or frozen.

Of the 2,541,125 children who were alive at the age of eighteen months, 30,959 (1.2 percent) were born from IVF. The team found that 103 of 6,959 children (1.5 percent) had an autism spectrum disorder and 180 of 15,830 children (1.1 percent) were diagnosed with mental retardation (born after an IVF procedure). The average follow-up period was 10 years.

Sandin and team found no association between IVF treatment and ASD, but did identify a small link between IVF and risk of mental retardation. When the analysis was restricted to single births from IVF, the risk of mental retardation was not statistically significant.

However, the authors said that “the results demonstrated an association between autistic disorder and mental retardation and specific IVF procedures with ICSI related to paternal origin of infertility compared with IVF without ICSI. The prevalence of these disorders was low, and the increase in absolute risk associated with IVF was small. These associations should be assessed in other populations.”

The researchers concluded:

“To the best of our knowledge, this is the largest study examining the relationship between specific IVF procedures and autistic disorder and mental retardation, examining the full range of IVF procedures. Our results should be applicable to most countries where IVF and ICSI are used. There are no major differences in equipment or laboratory work across countries but there may be some differences in choice of procedure.

For instance, in several countries (like the United States), ICSI is often used when the sperm sample is normal because of a presumed (but unproven) higher efficiency. Blastocyst [a structure in early embryonic development that contains a cluster of cells] transfer is infrequently used in Sweden but is more common in the United States.”

In 2010, researchers at Tel Aviv University, published research suggesting a strong link between IVF and mild to moderate cases of autism. The findings were presented at the International Meeting for Autism Research in Philadelphia.

Dr. Karin Middelburg, from the University Medical Center Groningen, Groningen, the Netherlands, reported in the 24th annual conference of the European Society of Human Reproduction and Embryology that singleton children born after IVF have no increased risk of neurodevelopmental disorders.

Written by Joseph Nordqvist