Ejaculated sperm has been shown to be significantly damaged by prolonged exposure to a WiFi connected laptop. A study, published in the journal Fertility and Sterility, found that after four hours of exposure there was a significant decrease in sperm motility and an increase in sperm DNA fragmentation.

'Our data suggest that the use of a laptop computer wirelessly connected to the Internet and positioned near the male reproductive organs may decrease human sperm quality', said lead researcher Dr Conrado Avendaño, from Argentina's Nascentis Centre for Reproductive Medicine. 'At present we do not know whether this effect is induced by all laptop computers connected by WiFi to the Internet or what use conditions heighten this effect'.

The researchers, based in Argentina and the US, took samples from 29 healthy males aged 26 to 45. Each donor's semen was divided into two samples. One sample was exposed to a WiFi Internet-connected laptop for four hours, while the remainder of the semen was used as a control.

The study examined sperm motility, viability, and DNA fragmentation. The results showed that 25 percent of the sperm under the laptop had no motion and nine percent showed irreversible DNA damage. Only 14 percent of the control sperm sample showed no movement, and three percent showed DNA damage. The results suggest that electromagnetic radiation emitted by wireless signals may be responsible for causing the damage to sperm.

While this may be the first study to evaluate the impact of laptop use on human sperm, further research is needed as the study relied on a small sample. UK fertility expert Dr Allan Pacey, senior lecturer in andrology at the University of Sheffield, said: 'The study is very well conducted, but we should be cautious about what it may infer about the fertility of men who regularly use laptops with WiFi on their laps'.

'Ejaculated sperm are particularly sensitive to many factors because outside the body they don't have the protection of the other cells, tissues and fluids of the body in which they are stored before ejaculation', Dr Pacey explained. 'Therefore, we cannot infer from this study that because a man might use a laptop with WiFi on his lap for more than four hours then his sperm will necessarily be damaged and he will be less fertile. We need large epidemiological studies to determine this, and to my knowledge these have not yet been performed'.

However, Dr Pacey still warned that men should be cautious about balancing a laptop on their laps for extended periods of time. 'We know from other studies that the bottom of laptops can become incredibly hot and inadvertent testicular heating is a risk factor for poor sperm quality'.