Utero is a Floor in The Binding of Isaac: Rebirth. It is the fourth stage of the game and it houses the Mom's Heart/It Lives Boss fight. It is also the alternate version of The Womb and is unlocked by killing all of The Womb Bosses.
- Growths are found in Necropolis. They will either contain nothing, shoot tears in an asterisk pattern, or contain a Red Heart.
- The Utero II will always have Mom's Heart (It Lives if unlocked) as the Boss in the Boss Room. The Boss Room cannot be exited through a door once entered.
- If Isaac has defeated Boss Rush and if he has beaten Mom's Heart (or It Lives) and if the time is under 30:00, the door to the Blue Womb will open.
- The theme for The Womb is Viscera.