Due to DDT’s massive prevalence in society and agriculture during the mid 20th century, DDT and DDE are still widely seen in animal tissue samples. DDE is [..] rarely excreted from the body, and concentrations tend to increase throughout life. The major exception is the excretion of DDE in breast milk, which transfers a substantial portion of the mother's DDE burden to the young animal or child
[1] https://en.wikipedia.org/wiki/Dichlorodiphenyldichloroethyle...
You would need to research the occurrence of autism among children of breast-fed mothers vs formula-fed (i.e. a cross-generational study). I'm not sure if that has been studied as extensively as you assume.
This sort of narrowly significant result is just the sort of research that is vulnerable to p-hacking and other biases. I'll wait for some supporting research before accepting something so weak, no matter the politics.
Reference: https://en.wikipedia.org/wiki/DDT#United_States_ban