Many studies have shown a correlation between the presence of toxic metals such as lead, tin, thallium, antimony and mercury in those on the autism spectrum (ASD).  Some studies have shown that the severity of ASD is directly related to the level of toxic metals present in the individual.
Autism Research Testing
Researchers funded in part by the Autism Research Foundation have conducted a nonlinear statistical analysis with cross validation indicating a strong association between urinary toxic metals (UTM) and autism.  Their studies included 67 children and adults on the spectrum compared to 50 neurotypical individuals of similar age and gender. First morning urine samples were collected and analyzed to determine the levels the presence of ten toxic metals.

The study found  a distinct difference between the presence of metals found in the participants with and without an autism diagnosis. The study did not result in recommended diagnostic testing, however, the result does show promise that future studies may result in such diagnostic testing.

It is important to note that the presence of toxic metals may result from many sources and may not be directly related to any factor resulting from either parent.  Toxic metals are found in drinking water, soils, some foods and other sources which may affect the individual prior to or after their birth.

Unlike many research papers which provide only an abstract for public viewing, this paper was fully published and may be read here.