But Dr Allan Pacey, a male fertility expert from Sheffield University was more cautious.

BBC: NEWS | Health | Surgery 'restores male fertility'

Dr Allan Pacey, senior lecturer in andrology at Sheffield University, says experts do not yet know exactly why.

BBC: Older fathers: what's behind the trend?

Dr Allan Pacey, senior lecturer in andrology at the University of Sheffield, told the BBC there was a need for such a pill.

BBC: Male contraceptive pill 'step closer' after mice studies

Dr Allan Pacey, senior lecturer at the University of Sheffield and secretary of the British Fertility Society, said some studies had shown an increased risk associated with some assisted reproductive techniques .

BBC: IVF 'not reason for birth risks'

Dr Allan Pacey, senior lecturer in andrology at the University of Sheffield, told the BBC that the idea had been discussed repeatedly but "experiments have never come close to suggesting it might work in humans".

BBC: Stem cell op may 'restore sperm'

But Dr Allan Pacey, a fertility specialist at the University of Sheffield and chair of the British Fertility Society, said the new rules enable donors to be properly compensated for their time, inconvenience and discomfort.

BBC: Egg sharing cuts Bristol's IVF waiting list

Dr Allan Pacey, senior lecturer in andrology at the University of Sheffield said it seemed intuitive that hot baths could contribute to reduced numbers of sperm but it was unclear whether it actually contributed to fertility.

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