Research has found that men using laptops on their knees will be doing damage to their fertility, even if they use cooling pads.

It is an accepted fact that using a hot laptop directly on your lap can increase the temperature of a man’s sperm, even by just a small amount, increasing the chances that his fertility levels will be reduced.

Researchers at the urology department of the State University of New York at Stony Brook monitored the scrotal temperatures of a number of subjects while they were using laptops. Some were using cooling pads; some had their knees open, while others had the laptops placed directly on the area in question.

All the males experienced a rise in temperature, though the subjects using pads or with their knees open did see the smallest change.

“Within 10 or 15 minutes their scrotal temperature is already above what we consider safe, but they don’t feel it,” the study leader, Dr. Yefim Sheynkin said.

Even an increase of just one or two degrees is enough to damage sperm and reduce a man’s fertility, though the doctors advise that if you must use a laptop on your lap, then keep your knees apart or use a cooling pad, as at least the options keep the temperature increase to a minimum.