I'm pretty sure that men would die - literally die - if they had to experience the pain of childbirth. My husband has a very high pain tolerance (once played half a game of rugby on a broken ankle, figuring it was just a sprain). However, when he watched me in the labor and delivery room, he said he actually felt sick to his stomach watching, because it looked so painful, and he was pretty sure I was going to die. (For the record, I was not about to die either time - these were pretty much normal deliveries.)
I have to hand it to the ladies who did it without medication - I had epidurals both times, and it still hurt! :-P