Utero

Utero is the alternate floor of The Womb, and looks exactly the same. The only difference is the variety of enemies and bosses that appear. This floor was added in the Wrath of the Lamb DLC.

Rooms

• 1: The room will always appear once in this floor
• 2: The room will always appear twice in this floor
• Possible: There is a chance for this room to appear, usually due to certain criteria being met
• -: The room cannot appear in this floor.

Rooms from the core game
Rooms	Utero 1	Utero 2	Utero XL	Note
Regular Rooms	22 - 26	22 - 26	39 - 40
Treasure Room	-	-	-	From The Womb/Utero and onwards, no more Treasure Rooms will appear.
Shop	Possible	Possible	Possible	Shops randomly appear in rare cases, higher chance if Steam Sale is owned.
Secret Room	1	1	1
Boss Room	1	1	2	Boss Rooms are always linked in XL floors.
Challenge Room	Possible	Possible	Possible	Will only be generated if Isaac has full health while entering the floor.
Arcade	-	Possible	Possible	Only generated when Isaac has 5 Coins upon entering a new floor or part.
Devil Room	Possible	Possible	Possible	If the Devil Room is entered at Utero 2/Utero XL, there will be a trapdoor leading to Sheol instead of items being sold for Heart Containers. The trapdoor appears even if the player has not killed It Lives!.
I AM ERROR	Possible	Possible	Possible	Only reachable by using the Telepills, which have a 6.66% chance to teleport Isaac to this room.
Rooms with Wrath of the Lamb
Rooms	Utero 1	Utero 2	Utero XL	Note
Super Secret Room	1	1	1
Curse Room	Possible	Possible	Possible
Sacrifice Room	Possible	Possible	Possible
Angel Room	Possible	Possible	Possible	If the Angel Room is entered at Utero 2/Utero XL, there will be a trapdoor leading to Sheol instead of an item at a pedestal. The trapdoor appears even if the player has not killed It Lives!.
Library	Possible	Possible	Possible	5% base chance to spawn, 25% if Isaac is holding a book.
Boss Challenge Room	Possible	Possible	Possible

Monsters

Monster	Description	WotL DLC
Fat Fly	Alternate version of Pooters. Fires 2 shots in a V-formation and does not deal touch damage.	✔
Spit	Flies slowly towards Isaac, exploding into an IPECAC shot upon death which targets other Spits in the room, or Isaac.	✔
Spider	Moves erratically around the room, damaging Isaac by touch.	✔
Big Spider	Moves erratically around the room, splitting into two Spiders upon death.	✔
Gazing Globin	Quickly walks towards Isaac, dealing one heart of contact damage. Turns into a pile of goo and slides away after taking enough damage, where it can be killed. Will regenerate after a short amount of time if not killed quickly.
Mask + Heart	Invulnerable mask with a slow-moving Heart. Functions similarly to a Knight. The Heart fires 4 blood shots in a plus pattern when Isaac gets near. Killing the Heart will automatically kill the Mask.	✔
Clotty	Moves around the room, firing 4 blood shots in a plus pattern.
Clot	Moves around the room, firing 4 tar shots in an X pattern.
Brain	Crawls around the room, leaving a trail of red Creep that does one heart of damage.
Guts	Attaches itself to a wall or obstacle, such as a Rock, rolling around the room.
Mama Guts	Slowly moves around the room, occassionally hopping and firing 8 large blood shots in all directions. Will split into 2 Guts upon death.	✔
Para-Bite	Moves towards Isaac. Can burrow underground and reappear elsewhere.
Fred	Fires an IPECAC shot at Isaac. Will hop out of the ground and burrow elsewhere, firing 4 blood shots in an X pattern while doing so.
Lump	Fires 3 fast-moving blood shots at Isaac when he gets in its line of sight. Will burrow underground and reappear elsewhere after firing its shots.
Leech	Quickly charges towards Isaac when he gets in its line of sight.
Kamikaze Leech	Quickly charges towards Isaac when he gets in its line of sight. Explodes with a large blast radius upon death.
Holy Leech	Quickly charges towards Isaac when he gets in its line of sight. Explodes with a large blast radius upon death. Has an Eternal Fly circling it.	✔
Double Vis	Charges up a Brimstone laser which fires from both sides when Isaac gets in its line of sight.	✔
Eye	Quickly fires a Technology-like laser at Isaac.
Bloodshot Eye	Quickly fires a Brimstone-like laser at Isaac.
Dople	Copies Isaac's movements, and fires tears at the same time as him.
Evil Twin	Copies Isaac's movements, and fires tears at the same time as him.
Baby	Fires a single blood shot at Isaac. Can teleport and reappear elsewhere.
Angelic Baby	Fires 3 blood shots at once at Isaac, has much more health than regular Babies.	✔
Vomit Grimace	Stationary and invulnerable monster that fires an IPECAC shot at Isaac. Stops firing when room is cleared.	✔
Minibosses (7 Sins) found in normal rooms:
Wrath	Usually paired with another Wrath. Fires Bombs at Isaac that detonate after a short amount of time, in a manner similar to Dr. Fetus.
Sloth	Usually paired with another Sloth. Fires IPECAC shots at Isaac, while occasionally spawning Chargers
Envy	Usually paired with another Envy. Moves around the room slowly at first, and then splits into two faster-moving heads after taking enough damage. These heads will split into two more heads with a smaller size and increased speed after taking enough damage, which will then split into the smallest heads that do not split.
Bosses found in normal rooms:
Blastocyst	Hops around the room, firing 4 large blood shots in a + pattern. Splits into two smaller parts upon taking enough damage, and into an Embyro at the end.
Gemini	Two joined twins that compose 50% of the health bar each. The large twin runs towards Isaac, while the smaller twin fires fast-moving blood shots. The smaller twin will stop firing blood shots upon the larger twin's death, and instead start chasing Isaac.
Fistula	Floats around the room diagonally, splitting into smaller, faster versions every time it takes damage. Smallest versions spawn a Charger when killed.
Gurdy Jr.	Spawns Pooters regularly, and can fire blood shots in all 8 directions. Will occasionally charge towards Isaac at very high speeds, bouncing off walls.	✔
The Husk	Moves around the room diagonally, spawning Flies and firing a large number of blood shots in short intervals.	✔
The Hollow	Two multi-segmented enemies that fly around the room diagonally, damaging Isaac by contact. All of the segments have to be destroyed for the boss to be killed.	✔
Loki	Constantly fires 4 blood shots in a plus or cross pattern, and sometimes in all 8 directions at once. Occasionally teleports around the room. Can spawn Boom Flies

Bosses

Teratoma

Lokii

The Bloat

Daddy Long Legs

Triachnid (Daddy Long Legs' Alt)

Death (Horseman of the Apocalypse)

Conquest (Death's Alt)

Mom's Heart (Final boss of Utero)

It Lives (Mom's Heart Alt)

Room-layouts

Battling Lokii.

Rebirth

Battling Mama Gurdy.

Mama Gurdy performing a vomit attack.

Trivia

• The name of this floor is based off a Uterus, the organ in the lower body of a woman or female mammal where offspring are conceived and in which they gestate before birth; the womb.
  

Chapters
Chapter 1	Chapter 2	Chapter 3	Chapter 4	Chapter 5	Chapter 6
The Basement The Cellar	The Caves The Catacombs	The Depths Necropolis	The Womb Utero	Sheol Cathedral	The Chest