Autism determined by prenatal factors - such as?

I think the widespread belief among scientists now is that autism is "determined by prenatal alterations in brain development."

But what causes these prenatal alterations???

I'm just curious if any scientist out there has thought to do any studies which might link autism to any of the following:

exposure of fetus to radiation from microwaves;
exposure of fetus to mother's use of birth control pills;
exposure of the fetus to too many ultrasounds;
exposure of fetus to harmful chemicals in mother's diet (artificial colors, preservatives, etc.)
exposure of fetus to harmful chemicals in everyday life (soap, laundry detergent, cell phone waves, etc.)

The brains of autistic children appear to be fine until age two when abnormal growth starts. It defies common sense to suppose prenatal determinants. Scientists have already thought of all possibilities. Here is a list of brain studies done in attempts to understand autism. You will see that those guys are leaving no stone unturned in their search.

http://www.autismspeaks.org/science/scie...

Incidentally; Sally is right. Genetics is "prenatal," but so far genetics has only been able to demonstrate a possible "predisposition" and is not a cause in and of itself.

yeah-something called VACCINATIONS Report It

You left out the main causes.
Vaccinations to the pregnant women containing mercury and aluminum.
Dental work done on silver(mercury) fillings while pregnant.

Studies have been done. vaccines cause autism.
"Kids who received 100 micrograms of thimerosal were over ten times more likely to have autism than the kids who received no mercury containing vaccines. "

Dr. Mark Geier

http://www.generationrescue.org/
http://www.vaclib.org/
Andrew Hall Cutler, PhD Harvard biochemist - www.noamalgam.com

You left out a major pre-natal factor: Genetics