Why do people keep saying childbirth? It's not like they have much other choice than to just withstand the pain. Are they supposed to just tell the kid "No, this hurts to much, so you'll have to stay in there." And as already mentioned, the body dopes itself to be able to go through that amount of pain, so it's hardly fair to compare that to something like "a kick in the balls", as that is a far more sudden pain that is hardly countered at all by the body.