I think that in the pic on which the new suika was born it showed that her horns were bending during the process, It probably hardens when the process is complete, like Kayjordan said.
Kayjordan17 said: Yeah, like rock candy or something.
If you have rock candy scraping against your vag I'm pretty sure it'll still hurt like hell. But like others have said it looks like it hardens after birth.