[Valpal1]

If the studies point to an interaction of genetics and environment, what genetics are different in 40yr olds that haven’t had prior pregnancies compared to those that have? Because it looks like the entirety of that difference is the exposures between age 25 and age 40. Ie, the environment. The older you are, the more ‘exposed’ you are. Else there would also be age differences in strictly genetically heritable diseases as well.

This does not compute. There is NO age differences in some strictly genetic diseases because there is no environmental component in them like the previously mentioned x-linked disorders. Age itself is an environmental factor, not just because of possible cumulative exposure to some third factor.

[Black Agnes]

” Age itself is an environmental factor, not just because of possible cumulative exposure to some third factor.”

Then the numbers of diagnosed kids of 40yr old mom’s wouldn’t depend on whether those kids were the first born or the tail end of 15 or more. So the increased numbers of asd kids wouldn’t have anything to do with whether or not their moms had had previous kids. And thus the increased numbers of asd kids wouldn’t be because women had ‘put off childbearing’.

Because until the 1940’s and 50’s, women generally had kids till they couldn’t anymore. Usually in their early/mid 40’s.