The report estimates that 1 in 68 children has autism spectrum disorder. The announcement is here. The actual report is here. There is a great deal of geographic heterogeneity in the data (Alabama 1/175, New Jersey 1/45) which I suspect has more to do with general differences in health care delivery rather than the environment.
The change in the prevalence is indeed worrying. One has to wonder whether this is a real increase or rather represents increased awareness of autism among those doing the diagnosing. It would also be very interesting to see the global data if it exists. I guess the other question I would have is what percentage of those diagnosed are high functioning (as in Aspergers).