United Kingdom, April 23 -- Demi Moore feared her daughter Rumer wouldn't "make it" through childbirth.

'The Substance' star was by Rumer's side when she delivered her little girl Louetta in a waterbirth at home, and Demi has now admitted she worried about her daughter's pain threshold.

She told PEOPLE magazine: "It was really incredible ... Rumer had a home birth, and there was a moment when I thought: 'Oh boy, I don't know if she's going to make it', like she has a different pain threshold than I do.

"To just see her move into her own power and focus, it was a really extraordinary, beautiful moment."

Rumer, 36, previously admitted she was terrified about giving birth even though she was following the plan she set out to deliver her ...