mmred a few impotrtants point
first, most people do accept that asd is caused only in a very few cases- 8% is a figure I seem to recall- by MMR.
ASD is a very complex illness and nobody knows the aetiology of it at rpesent, it seems most likely that many cases have a genetic basis for which a trigger is usually required, and once you get to that level identifying the trigger becomes complex. Even when you look into famillies where there does seem to be a clear asd genetic issue, there is always the risk of spontaneous gene mutation and increased asd risk, plus potential otehr causes.
The important thing to note is that ASD is not one syndrome, but most likely a number sharing a certain number of characteristics; as such there could be a great many causes, from MMR to diet to birth damage to viral infection.
I ahve 2 with asd, and we new ds4 was at a high risk, and indeed I did start tot hink indeed he was but altely (he's at that crucial age- 17 months next week) he ahs started developing non ASD skills; has a great point, chatty etc.
I would guess (also based on such things as a dietray issue inherited by every other spectrum family member, a casein intolerance) that ds4 has the gene: so something we are doing is staving it off. He is BF, on a CF / GF diet, has intensive input in language, no MMR- even if it is one of thsoe I can never even guess at which, or if there's an environmental factor such as lack of pollution (we moved from along the A38 to semi- rural Wales when ds3 was almost2......) bt something IMVHO is changing with him