Killing baby zombies don't benefit you in any way. They don't drop xp, rotten flesh or anything. If you get killed by a baby zombie that can pick up your armor and sword, then there is no way getting those items back. Also, this is the same with baby pigmen.
Duplicate of MC-4150, please use the search function to see if your bug has already been submitted. Currently over 56% of tickets are being resolved as duplicate.