Summary: <p>Mother's day is nigh. Sort of. Anyway, without knowing it, you might have already given your mom a pretty lasting gift. But whether it helps or hurts her, or both, is still an open question. In this Radiolab short, Robert updates us on the science of fetal cells -- one of the first topics he <a href="http://www.npr.org/templates/story/story.php?storyId=5195551" target="_parent">covered</a> as an NPR science correspondent.</p>
