Bear in mind that i can take 24 hours from pip to zip. If it has slowed down it may be resting. You don't want to pull it out before it has a chance to absorb the yolk sack and for the navel to close. Believe me, i have been there, jumping in to help too soon, and not always with the best outcome. i wouldn't start to worry and consider helping until a full 24 hours has passed since pipping.
