Yeah, the Gauntlet wouldn’t leave anything that can’t survive on its own, like gut bacteria, nor remove anything that’s needed for the proper functioning of another lifeform. It’s why there weren’t any fetuses falling to the ground after the pregnant women vanished.
I would assume that conjoined twins would be a both-or-neither situation, since removing one would leave a gaping wound in the other even if they could have survived independently with surgery,