Part of the problem with helping them is that we don't really know what day/time they should actually slit the egg...so if they are struggling and its too soon the baby might not make it anyhow.
Of course, the other side of the coin is...if they are supposed to be slitting the egg and can't they will die trying. Its usually said that if the baby can't get out on its own, it won't likely be strong enough to live anyhow.