All human Zygotes start out as female, and a burst of androgens makes some fetuses develop male sexual characteristics. If those androgens aren't released, the

All human Zygotes start out as female, and a burst of androgens makes some fetuses develop male sexual characteristics. If those androgens aren't released, the child retains female sexual presentation, even if they have XY chromosomes. As is commonly mentioned, this is why men have nipples even though they're not functional for men. According to my very weak understanding, it's easier to prevent that from happening than it is to accidentally introduce enough xenoandrogens to cause a XX fetus to develop male sexual characteristics.