It is accessed by defeating Mom's Heart or It Lives! within 30 minutes. Leaving and re-entering the Boss Room after the timer has reached 30 minutes will make the entrance to the Blue Womb disappear.
If the player is fast enough, both Boss Rush and Blue Womb can be completed in a single run.
It contains the following:
- 4 golden chests in the main room.
- Unlike the ones in The Chest, these are just regular golden chests and don't guarantee an item drop.
- 2 locked Treasure Rooms, both of them offering two choices of items as if More Options was active.
- A Shop that always contains 6 items, even if Shop Upgrade Lvl. 4 has not been unlocked.
- A 2x2 boss room that contains Hush.
- The door leading to the boss room might blend in with the northern wall, but will slide away upon approaching it.
It is advised to enter the Blue Womb only with very powerful items and/or a set of good dodging skills, because Hush ranks amongst the most difficult bosses of the entire game.
After Hush is defeated, one of two things will happen:
- If this is the first time Hush has been defeated, a giant golden chest will appear in the middle of the room. Jumping into it ends the run and gives ending 17.
- If Hush has been defeated before, a trapdoor and a beam of light leading to Sheol or The Cathedral will appear.
- This floor cannot be skipped with We Need to Go Deeper! or the Ehwaz rune; both will have no effect.
- The floor can be skipped if a Black Market is found.
The Blue Womb's music is called Mater Prope or Nativitate. The tracks that play during the battle against Hush are called Ascension (the Blue Baby fight music; played during Hush's first phase, which is similar to Blue Baby) and Morituros (during the second phase).
- The displayed name of the chapter is ???, but the chapter is referred to as Blue Womb by the achievement, using the same logic as the character ???.
- The character ??? and the Blue Womb have the same unlock requirements.
- Blue Womb is unique as the only chapter that can be optionally done between mandatory chapters.
- Blue Womb is the smallest chapter, only containing 5 normally accessible rooms.
- In Isaac's last will, the Blue Womb is referred to as "some barren place".
- The names given to the soundtrack which plays in the Blue Womb (Nativitate and Mater Prope) are in Latin, and translate to "Birth" and "Almost Mother", respectively.
|Chapter 1||Chapter 2||Chapter 3||Chapter 4||Optional||Chapter 5||Chapter 6||Endgame|
|The Basement||The Caves||The Depths||The Womb|
|The Cellar||The Catacombs||Necropolis||Utero||???||The Void|
|Burning Basement||Flooded Caves||Dank Depths||Scarred Womb|
|The Basement||The Caves||The Depths||The Womb||Sheol||The Shop||Ultra Greed|
|The Binding of Isaac: Rebirth|
|Achievements||Attributes||Bosses||Cards and Runes||Challenges||Chapters|