Working on a laptop wirelessly may hamper a man's chances of fatherhood. In a study, sperm placed under a laptop connected to the internet through wi-fi suffered more damage than that kept at the same temperature but away from the wireless signal. The finding is important because previous worries about laptops causing infertility have focused on the heat generated by the machines. In the latest study, researchers took sperm from 29 men aged 26 to 45 and placed them either under a wi-fi connected laptop or away from the computer. The laptop then uploaded and downloaded information from the internet for four hours. At the end of the experiment, 25% of the sperm under the laptop had stopped moving and 9% showed DNA damage. By comparison, just 14% of samples kept away from the wi-fi stopped moving. And just 3% suffered DNA damage, the journal Fertility and Sterility reports. The wireless connection creates electromagnetic radiation that damages semen, the scientists, from the United States and Argentina, believe.