In the first place, all matter that falls within the event horizon of a black hole end up in the singularity mass at the center of the black hole. Due to the Casmeer effect, a vast amount of negitive energy must exist between the event horizon and the singularity (at least the black holes mass worth), so macroscopic wormholes could exist inside the event horizon. But due to the extreme curvature of space time inside the black hole, the wormholes exit vactor will still be inside the event horizon of the same black hole, so anything trying to escape the black hole that way still ends up ultimately hitting the same singularity anyway.