In pain you shall bring forth children

A few days ago, I was pondering on this fragment from Genesis when God expelled people from paradise

To the woman He said: I will greatly multiply thy sorrow and thy conception; in sorrow you shall bring forth children...

Gen. 3:16

I wonder, were there any other options before this? Was a woman's body arranged differently before the expulsion? Were the passages wider, and was it planned that the child would just jump out from there?

Or did God add nerve endings after the expulsion to make it more painful? Nausea, a heavier stomach, swollen legs and other sorrows.

How could it have been different physiologically if the human body structure didn't change?