I actually have come across this before. Scientists have proven that testicular overheating when a man is seated for long periods of time, made even worse with heated car seats, affects fertility in men. It was also found that any occupation that involved spending a great number of hours driving took them longer to conceive. Also, sperm counts of professional drivers were lower and that the sperm itself contained more abnormalities. If I could find the links to the original studies I would put them here, but I do know that some of this information is from a study by New Scientist magazine.
It doesn't stop with driving, though. Sperm quality is also detrimentally affected by high exercise intensity and volume...
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