I just hatched this Pichu, and while I was checking the stats, I noticed that it was missing 27 HP. I haven’t used it battle, or anything, so why does it need to be healed?
This is the result of a recurring bug in Pokemon GO, that often hits when Niantic rebalances a Pokemon's stats. As mentioned in the link:
It will fix itself as you hatch all of your eggs obtained before [a] stat rebalance. They just forgot to update the current HP of pokemon still in eggs when the rebalance hit. You'll just need to heal or toss the hurt pokemon that you hatch.