It's always been something of an urban legend that men leaving a scorching notebook computer on their lap were damaging their sperm, but new research suggests that such conjecture has a basis in scientific fact.
According to a new report in the journal Fertility and Sterility, researchers found that 29 male test subjects who used a laptop while holding it on their knees raised the temperature of their scrotums to an unsafe level within 15 minutes -- even when their laps were "protected" by a pad covering them. Pads weren't effective at cooling testicles because the biggest impact was related to the legs being kept together in order to balance the laptop on the knees. A urologist leading the study says that an increase in scrotal temperature of roughly two degrees Fahrenheit is enough to impact sperm quality.
So while there's no direct link established yet between one's sperm count and laptop use, there appears to be a indirect connection with men using a portable PC, their scrotums overheating, and such overheating being sufficient to damage sperm. It's at least something to think about if you're a heavy laptop user and you'll trying to conceive a child: Maybe you want to rest the computer on a desk more often.
One urban legend that the study appears to have put to rest, however, is that the belief that wearing tight pants and underwear affects sperm quality. So feel free to sport those snug jeans and tidy-whities -- just don't place a running laptop on top of them.