Male cells can be found during autopsy in the brains of women who are 60, 70, or older.
The cells have everything they need to survive in the mother’s body. I think that the cells that cross the placenta are not programmed to develop further, but simply to integrate themselves into the host (mother) and survive.
I hypothesize that this may be one reason the immune system does not recognize the baby as a foreign invader and kill it—because the baby’s cells become part of the mother’s body, therefore causing them to be recognized as “self” by the immune system. A related function may be that the presence of the children’s cells strengthens the maternal instinct.
I can tell my sons that they will always be a part of me...
AND, Mary had cells from Jesus with here the rest of her life ...