What the ♥♥♥♥ causes you to take full heart of damage ?

[GrimStrider]

I know that colored enemies (champions) do inflict 1 full heart, and spikes too.

I play a regular challenge or a regular run - everything goes fine, half a heart damage all the time but all of a sudden - i begin to take 1 full heart, even with blood banks and demon judgements. What the ♥♥♥♥? Is that because of ceremonial robes ? Or the pact ? I just don't get it.

And ♥♥♥♥♥♥♥ pissed too. Failed a challenge for the second time because of that ♥♥♥♥.
Thanks in advance for the answers!

[Rubyeyed]

You take 1 heart dmg when you are on the womb and above.

[Monty]

Yep, that's how The Womb / Utero stages (and any later ones) work. Have fun! :)

[GrimStrider]

Thanks a ton, guys! <3
I had no clue that it was the case. Stupid me
Thanks again~

[FaelisongTalim]

If you're having serious issues with this mechanic, strive for the Wafer. Wafer is found in both Angel Rooms and Item room, and reduces ALL damage to a 1/2 of a heart, even before the Womb.

[AutumnLeaf]

There are some attacks before the Womb that'll take a whole heart off, too, like being hit by one of Monstro's large shots or running into the Haunt.

[Solo Death]

There are numerous things that can do this. monstro's large shots, famine charging into you, spikes, champion enemies, and everything past the womb.