this is the sort of question that doctors are really bad at answering. It's more of a personality test than anything. I know one thing, a researcher that concludes that cycling usually doesn't cause problems with the male reproductive system is unlikely to garner any attention, but saying that it means no kids will get you in every paper in the U.S. Of course, I don't doubt that a broad study would reveal some cases of reproductive problems, but that's true of people that only exercise by walking back and forth to the refrigerator for beer.

I've had numbness, but it's only on a fairly rare basis. Same thing for the last 35 years or so. I racked up thousands of miles per year when I was in my teens and early twenties. This didn't stop me from having kids. I might worry about a 11-16 y.o. boy not telling me about this, but I'm guessing that if it happened every day for a week, even the shyest kid would say something.