Mama Guts is a monster first added in the Wrath of the Lamb expansion, and also return in the Rebirth remake. They first appear in Chapter 4.
It appears as a large blob of internal organs, much larger than regular Guts.
Behavior

Mama Guts from the original game.
Instead of attaching to an object, they slowly move around the room, eventually firing 8 large blood shots. Killing it will cause it to split into 2 Guts.
Eternal Champion Behavior
It fires 8-way bullets in a single rapid session. Upon death, it spawns 2 Eternal Guts and 1 Eternal Clotty.
Notes
- From the Afterbirth DLC for Rebirth, Mama Guts has a chance to spawn 1 or both Scarred Guts upon death.
Trivia
- From the original game, they can be found in Necropolis. They no longer appear in this chapter from Rebirth, however.