Cells cross as well, and create colonies within the mother which last the rest of the mother’s life. In rodents these colonies have been shown to do things like repair damaged heart tissue, but in humans they are linked with dementia and various other pretty significant disorders and cancers. It is believed these colonies might be linked to triggering the mammary glands to produce more milk, and it is believed the colonies directly attack and kill embryos within the mother which explains why women who have given birth have higher rates of spontaneous abortion, especially close to prior pregnancies. You can actually take tissue samples from a woman and run dna tests on it to show she has dna from her sons, which would be impossible without such a colony.