On the Asimov’s blog, I listed eight little weirdnesses that inspired my new horror story about motherhood. Here’s number two:
In mammals, fetal cells migrate into the mother’s body. The maternal immune system eliminates many of these cells, but some integrate into the host tissue, where they may remain for decades, or even permanently. This makes mothers “micro chimeras,” organisms with distinct sets of genetic material. Little is known about the impact on mothers, or the evolutionary value of such a phenomenon.
More over at From Earth to the Stars. You can find the story itself in the September/October issue of Asimov’s Science Fiction.