After exposing men to 'wet heat' for 30 minutes on alternating days, researchers found a temporary decline in sperm production but did not look at sperm quality before and after the study.

BBC: Last Updated: Monday, 5 March 2007, 11:20 GMT

While the study took into account factors that can affect sperm quality, such as age, researchers were unable to control for socio-economic factors, smoking or weight, which have been shown to have a major impact.

BBC: French sperm count 'falls by a third'

In a previous study, Agarwal and his team found that men who used their cell phones more than four hours a day had significantly lower sperm quality than those who used their cell phones for less time.

CNN: Cell phones can affect sperm quality, researcher says