I have blogged several times about Caroline Rodger’s idea that sonograms during pregnancy greatly increase the risk of autism in the fetus. Her idea is supported by several lines of evidence, as she explains in this talk.
A new study provides more evidence. It found a high concordance rate among fraternal twins. In the general population from which the new study was drawn (California), about 1 child in 100 has autism. But if you are an identical twin, and your co-twin has autism spectrum disorder, your chance of having the same diagnosis is about 70%. The crucial point of the study is that the concordance was also high for fraternal twins: about 40%. As one commenter put it, this result “puts a spotlight on pregnancy as a time when environmental factors might exert their effects”.
Another study found more risk of autism if the mom took an anti-depressant during pregnancy. This supports the idea that a bad prenatal environment causes autism.
Thanks to Paul Sas and Gary Wolf.