It takes VERY little pressure to a man's groin to bring him to his knees. While it may hurt a woman to kick her full force in the groin, the same amount of force to a man would almost certainly make him black out.
The amount of pressure that it takes to make a man quite uncomfortable, when applied to a woman's groin area, would doubtfully cause much discomfort. It's difficult for a woman to understand.
Here's a way to try to explain it. Take one hand and hold it up flat. Now take your other hand and squeeze your fingers together (from the index and pinky inward). About the amount of force it takes before your fingers (in a relaxed position) give in and on folds under the other, would be enough force to make a man stop what he was doing and just a tad more pressure will have him on the ground.
Giving increasing pressure will cause the pain to radiate all the way up into the stomach. A swift blow will immobilize a man for probably 5+ minutes. (Been there)
If the pain of a rough groin kick were to extend over a period as long as childbirth the man would likely be in and out of consciousness constantly and would wish he was dead. The fact that women seem to be able to retain consciousness during childbirth makes me question how it compares to a full force groin kick. I'm not gonna say it's not horribly painful though becaues I'm sure it is, especially stretched over such a time period.
