Placenta

Effects

Grants one full Red Heart container when picked up.
Isaac has a chance to regenerate a Half Red Heart every time the in-game timer hits a new minute (00:01:00, 00:02:00, etc).
(Added in Repentance) Heals 1 additional heart of health.

The regeneration can happen multiple times in the same room, so there is no need to move between rooms to continue regeneration.
- (Removed in Repentance) However, regeneration does not occur when standing in a (Crawl Space) Crawl Space.
Regeneration will only occur when Isaac has Red Heart containers or something equivalent:
- (Keeper) Keeper's and (Tainted Keeper) Tainted Keeper's coin hearts will regenerate, one coin at a time.
- (Added in Afterbirth †) (Bone Heart) Bone Hearts regenerate like red hearts.
- Consequently, characters with no applicable health -- (???) ???, (The Lost) The Lost, (Dark Judas) Dark Judas, (Tainted Bethany) Tainted Bethany, (Tainted Judas) Tainted Judas, and (Tainted Lost) Tainted Lost -- do not benefit from the effect.

(Added in Repentance) Blood Oath: With enough patience, health can be safely restored each floor by waiting in the starting room.
Gnawed Leaf: Regeneration works while turned to stone, allowing Isaac to become invincible and regenerate while in any room.