The research that I have done says environment toxins, vitamin D deficiency and genetics are some of the main risk factors for Autism. This web site http://www.vitamindcouncil.org/health-conditions/neurological-conditions/autism/?gclid=CJmcjJ_2yqsCFQx3gwodU0KO0Q also talks about how pregnant women need to take vitamin D while pregnant to help from preventing their child from getting autism. it also says that areas with more cloud cover and rain, there are likely to be more children born with Autism. Check it out its a great website