Neither make much sense in isolation because when we think of ‘old’ or ‘late’ age, we think of ages at which giving birth isn’t possible.
If it were possible for me to give birth in my 60s, I wouldn’t want to. (Hypothetical)
I don’t want to be an older mother. (=Older than most mothers)
I’d never have a kid in my 40s. (Some women do, but that’s too old for me)