At a population level, we're ridiculously resilient. Or we wouldn't be here today in the numbers that you see. I just don't see PTSD being maladaptive enough. Maybe if you were born with it and were so dysfunctional that you couldn't interact at all with the opposite sex? Otherwise, I don't see it. There are too many other factors that are important for procreation for PTSD to override all of them.