I literally just woke up from a deep sleep remembering this thread because I think I've found a way to do this. A few months ago I graduated from a taxidermy class and I too thought how I could preserve an aborted fetus. I'm sure I could get the right tanning agents, bacteriacide, and some type of skin toughener which I haven't figured out yet.
So yeah, it would be neat to have a little well preserved fetus I could carry around for good luck or a conversational piece. Probably hybrid resin heat shrink wrap the whole thing after I finish the work on it.