It is called fetal dna I believe. It is something that happens in pregnancy that attaches to their brains and never goes away.
Now I am not saying that it verifies or proves anything. All I am saying is, when it comes to things like this there is much to learn and many things undiscovered as of yet. So I am "unconvinced" at this point. It is still a point of discussion of people who claim to have gotten males from verified feminized seeds. Whether it is true or not has been debated back and forth ad naseum. I am undecided.