I once saw it in a secular pregnancy book. Haven’t heard it from Rabbonim though.
Even with an epidural the process is not painless. Being numb, emotional roller-coaster etc is not conidered pain-free, like a regular Monday afternoon. Why shouldn’t we seek to minimize pain? “Hani kivshi d’rachmana lama lach?”. Not arguing, just asking and possibly explaining all the poskim who haven’t assusred this.