Research shows that cells from a baby circulate in the mother's bloodstream. By full term, 6% of the DNA circulating in the mother is from the baby and although it rapidly disappears after birth, some DNA-bearing cells remain. Some of those cells from the baby are stem cells. Here is the mind-blowing detail: These cells have been shown to pass into the brains of pregnant mice; new moms have been shown to grow new grey matter in their brains. Is it possible our babies integrate themselves into the circuitry of our minds? The baby's DNA includes some from the father and may end up being integrated into the mother's body too. This is astonishing. Fetal cells may perform repairs in the mother because they are known to migrate to sites of injury. It's also possible the immune cells circulating from the baby help protect the mother from disease by borrowing from the father's immunity toolbox. As author, Jena Pincott, writing at Boing Boing says, "This is the truly startling stuff". She has written a book, Do Chocolate Lovers Have Sweeter Babies? The Surprising Science of Pregnancy.
(Above material quoted and paraphrased from the Boing Boing story. where a lot more material can be found.)
h/t Hot Air.