A particular type of in vitro fertilization (IVF) called intra-cytoplasmic sperm injection (ICSI) is associated with a higher risk of autism and mental disability in children, compared with standard methods.
ISCI is a procedure in which a sperm is surgically extracted from the testes and then injected directly into an egg before being transplanted to the womb.
The study — led by researchers at Karolinska Institutet, the King’s College London, and the Mount Sinai School of Medicine in New York — analyzed data from the Swedish national registers.
“We tend to think about IVF as just one single method, but IVF treatments are vastly different in terms of their complexity,” said study author Sven Sandin, a biostatistician at Karolinska Institutet.
“When we looked at IVF treatments combined, we found there was no overall increased risk for autism, but a small increased risk of intellectual disability,” he said.
“However, when we separated the different IVF treatments, we found that so-called 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.”
The researchers analyzed more than 2.5 million birth records from 1982 and 2007, and followed up to see whether children had a clinical diagnosis of autism or intellectual disability (defined as having an IQ below 70) up until 2009. Overall, 1.2 percent (30,959) children were conceived through IVF. Of the 6,959 diagnosed with autism, 103 were born after IVF, and of the 15,830 with intellectual disability, 180 were born after IVF.
Researchers compared all six different types of IVF procedures available in Sweden. They investigated whether fresh or frozen embryos were used, if intracytoplasmic sperm injection (ICSI) was used, and if so, whether sperm was ejaculated or surgically extracted.
ICSI is a common procedure for male infertility and is now used in about half of all IVF treatments. The technique involves injecting a single sperm directly into an egg, rather than fertilization happening in a dish, as in standard IVF.
The findings show that babies born after IVF treatments with ICSI (with either fresh or frozen embryos) had a 51 percent increased risk of intellectual disability, compared to children born after standard IVF (fresh or frozen embryos).
Even when other known risk factors for autism and developmental disabilities, such as multiple births and premature births were taken into account, ICSI remained as a risk factor.
Still, intellectual disability or autism remains a rare outcome for IVF treatment with ICSI, researchers point out.
“It is important to remember that the majority of children are born perfectly healthy following IVF,” said study co-author and fertility specialist Karl-Gösta Nygren, M.D., Ph.D.
“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. Our study also provides further evidence for the need to minimize multiple embryo transfer.
“However, more research is needed to elucidate the reasons behind our findings.”