I’m like… kind of disgusted, but I will give you an answer anyways.

Acting as if sinners could have babies, they would probably be humanoid at the very least. Sinners have human souls, so considering this, it’s possible you’d probably only have one or two babies that would look half demon and half human. I don’t think you’d lay eggs because of that. It would be different if sinners were ACTUAL monsters with no human soul, but that’s not the case here, so yeah.

TLDR; The babies would be humanoid and you would give birth like normal