IVF Tied to Small Risk of Mental Deficits in Kids
Large Swedish study did not find higher risk for autism
There is still a chance, however, that certain IVF procedures carry a risk.
Sandin's team found that a specific IVF technique used for male infertility -- called intracytoplasmic sperm injection, or ICSI -- was related to an increased risk of intellectual disability, even among single babies.
Again, the actual rates of intellectual impairment were quite low, Sandin said. But the results suggest there could be something about the intracytoplasmic sperm injection, or fathers' infertility, that contributes to the risk.
"People have for some time been concerned about the ICSI procedure," Cedars said.
That is partly because intracytoplasmic sperm injection is invasive: A single sperm is injected directly into an egg, whereas in standard IVF, sperm fertilize the eggs in a lab dish. "[ICSI] also bypasses the natural selection of sperm" that happens during fertilization, Cedars said, in which sperm compete to penetrate the egg and the fittest one wins.
But an alternative explanation is that male infertility -- which may involve genetically abnormal sperm -- is raising the risk of intellectual disability, rather than some effect of intracytoplasmic sperm injection, Cedars said.
Sandin agreed, but said it's impossible to say for sure based on these findings.
The study corroborates past research that has found no excess risk of autism after IVF. But this is by far the largest and best designed study to look at the question, Cedars said.
"This gives us powerful evidence that there is no association with autism," she said. She added that expectant parents can also be reassured that the risk of intellectual disability linked to intracytoplasmic sperm injection is still very low, even if it's higher than the norm.
Although the study found an association between certain IVF procedures and a higher risk of intellectual disabilities in children, it did not establish a cause-and-effect relationship.
Cedars and Sandin both said more studies are needed to see how children fare after IVF, and to dig for reasons for the current findings on ICSI.
Between 1978 and 2012, about 5 million children worldwide were born via IVF, and the numbers will only increase, Cedars said. And in some countries -- including the United States -- intracytoplasmic sperm injection is being increasingly used in cases in which there is no clear problem with the man's fertility, because there is a perception that it's more efficient.
But that belief, Sandin's team said, is unproven.