Bingowings:
Would a woman pregnant with, say... two Jedi twins start moving things around the room with her mind?

They would have a shared blood supply.

Hehe I know what you mean. But taking your question literally, you're actually incorrect about that. Mother and baby do not share the same blood supply. Any exchange of oxygen and nutrients happens through the membranes of the placenta, and the blood supplies of both never mix. Think about it; a baby can have a completely incompatible blood type to its mother, so mixing could be very harmful, even fatal, to both. Also, they would have identical heartbeats if they only had one blood network.

It's also for this reason that a baby carried by a woman who is HIV+ amazingly has only a 30% chance of being HIV+ itself, and the vast majority of that 30% happens during delivery. Sounds incredible, but that's why.