Autism Now

I saw something on TV about autism now be detected in a fetus is it true?

Known genetic disorders that we know contribute to autism, ie, fragile X syndrome and Rett syndrome, the diagnosis can be made before birth.

Until a definitive gene, or group of genes, which are identified and known specific to autism I do not see how they can specifically screen for autism if it is autism which is the result of one of the two conditions above, or other known syndromes that have a high incidence of autism.

It would be similar to testing for Down syndrome.