Babies have a few tricks up those pudgy arm sleeves
Babies are designed to extract more resources than mothers prefer to give (this is of course on a non-conscious level - I’m primarily talking about physiological processes here). As the fetus grows inside your body, it causes the expansion of maternal arteries as well as an increase in blood pressure in order to extract more nutrients from the mother’s blood. When this process becomes disrupted, women can get pre-eclampsia (high blood pressure during pregnancy that can be quite dangerous to both mom and baby).
Spit or swallow?
If you want to reduce your chances of pre-eclampsia, you might consider monogamy and blowjobs…seriously! Scientists found that prolonged sexual exposure to one male prior to pregnancy - including the swallowing of his semen - correlated with a reduction in pre-eclampsia risk in women. Of course there are numerous risk factors for pre-eclampsia and this is a correlational study.
Your baby leaves your body after 9 months, but they may leave something behind!
If you’ve been pregnant for longer than 6 weeks, there is a good chance that your body contains cells from your fetus - not just in your uterus! This phenomenon is called fetal microchimerism and it means that you can have your baby’s cells in your heart, brain, lungs, and more! In an analysis of one woman’s c-section scar, it was found that fetal cells migrated to the incision site and possibly played a role in healing.
There is more to the mystery though - fetal microchimerism may also play a role in some cancers! It’s a really new research area, so stay tuned! This also means that younger children in a family can contain cells of their older siblings and that mothers can contain cells with Y chromosomes (if they've been pregnant with boys).
For further reading (in order of the above list)