Tanby -
It is generally around the 9month to 1year mark that children who are autistic start to show symptoms which is probably what prompted your doctor to comment on it. I believe that is one of the reasons the MMR gets so much attention - because symptoms of autism arise around the same time as that particular immunization.
Both of my parents, my step-mother, and a very good friend are all registered nurses, plus another friend is a lab technician and her husband is a GP so I am VERY pro immunization. So much so that DH and I enrolled DS in an immunization study at the childrens hospital. As a parent I take risks every day with the decisions I make for DS - some are more risky than others - I admit - but I feel that the risks of the immunizations are much smaller then the risks of the diseases themselves. Just my personal opinion...