One possible source of autistic disorders might be the ultrasounds that expectant mothers undergo during their pregnancy. Previous generations would do one or two ultrasounds, if that many. The number now is much greater. Improving technology, including the ability to see the ultrasound in real time and to adjust the sonic rays so as to create a more three dimensional view, and the dropping prices that come with common adoption of technology, mean that mothers are sometimes getting twenty or thirty ultrasounds over the course of their pregnancy. Although this does much to set their minds at ease, there is serious concern that these ultrasounds are affecting fetal brain development.
Ultrasound sonograms use concentrated, high frequency sound waves to create pictures of the fetus in the womb. These sonic vibrations, delivered at low volume but at very high frequency, pass through the entire body of the fetus, including the brain. It is not known precisely what changes these sound waves may cause, but a 2006 study on laboratory mice proved that ultrasonic exposure changes the way that neurons distribute themselves in developing brains. Multiple exposures showed progressively greater migrations of neurons. Although the precise ramifications of these changes are not known, it is reasonable to surmise that this may have a deleterious effect on the fetal neural system.
No correlation between ultrasound exposure and any other disorder has yet been proven, but scientists are working hard to gather evidence and test this hypothesis. If there is a connection between ultrasound and autism, then there will certainly be major changes made to prenatal treatment across the world.