AshleyTheAmazon

“Six years ago I reported on Morning Edition that whenever a woman gets pregnant, some of the baby’s cells slip through the placental wall into the mother’s blood and settle down for a while — outside the placenta.

Then, when the baby is born (or fails to be born), most of those cells disappear. After all, the baby’s DNA is different; it’s a combination of mom and dad. So in the genetic sense it’s a foreigner and doesn’t belong in mom any more. “One would expect [fetal cells] to be attacked fairly rapidly,” said Dr. Kirby Johnson of Tufts University.

But here’s the surprise: some of those fetal cells stay.

And stay.

And stay.”

Science, you so crazy.