While new research finds no significant link between autism and singleton children conceived via in vitro fertilization (IVF), a slightly increased risk of mental retardation, or intellectual disability, was found following IVF treatment including intracytoplasmic sperm injection (ICSI).
ICSI involves the injection of a single sperm into an egg to fertilize it. Researchers found when ICSI was used to overcome male infertility, the risk for intellectual disability increased slightly compared to IVF without ICSI.
"The reasons (for an increased risk) could be the underlying infertility," says Abraham Reichenberg, one of the study authors and a professor at Mt. Sinai School of Medicine in New York and King's College London.
"It could be something happening in the many steps that are involved in each of the treatments, or something that's happening later in the pregnancies, or all of them combined together. It could be any one of those steps. In any one of them it could go wrong." The increased risk was seen even in singleton births utilizing ICSI. However, the overall risk remains low.
There were about 91 children diagnosed with mental retardation (per 100,000 person follow-up years) when conceived by IVF using ICSI with ejaculated sperm and fresh embryos. That's compared to about 61 children diagnosed using IVF without ICSI.
While no link was seen between autism and singleton children conceived via any form of IVF, study results did show a four-fold increase in the risk of autism in children conceived under the most severe forms of male infertility (in which sperm must be surgically extracted) compared to less severe forms of male infertility, but even that risk only showed up in twins.
"I think this study gives reassurance to both physicians and patients that there doesn't seem to be an association with IVF (and autism) in general," says Dr. Marcelle Cedars, professor at UCSF medical center in San Francisco.
"There may be a very small risk with some of the technologies used for male factor infertility and I think those are things that couples should be aware of, but I think that overall the study was reassuring and, despite the fact that couples frequently come to us and say 'I want twins, I want to transfer more embryos', I think this gives us more ammunition and more information to share with couples to try to encourage them to try to get pregnant with a singleton."
"The single embryo treatments are safer," Reichenberg says. "There are less birth complications, less pre-term births, the birth weight is better, all different neonatal outcomes are better in single embryos."
The study, published Tuesday in the Journal of the American Medical Association (JAMA), tracked 2.5 million infants born in Sweden between 1982 and 2007, including 30,959 total infants conceived by all available types of IVF treatment.