I can only speak for my side of the species but being kicked in the balls, and I mean a really hard kick in the balls basically paralyses a guy in pain. The pain itself travels from the balls (obviously) up to the throat! You gasp for breath, you try to stand but your whole body is racked with pain. You simultaneously feel like you been kicked in the nads, winded, smacked in the throat and are being suffacated at the same time!
Clearly not a pleasant experience, and this pain lingers for a long long while. Having not gone through childbirth, I can't compare but obviously they both really hurt.
On the other hand, what I have been told is very close to the pain of childbirth is having testicular cysts, and these little babies feel like you've been kicked in the nuts permanently and that someone is hanging a weight from them. Fun times, I think you'll agree!