Men who keep a mobile phone in their trouser pocket could be inadvertently damaging their chances of becoming a father, according to a new study.
Scientists at the University of Exeter said their work suggested that exposure to radio-frequency electromagnetic radiation from mobile phones negatively affected sperm quality - but further research was needed.
Previous studies have suggested that radio-frequency electromagnetic radiation (RF-EMR) emitted by the devices can have a detrimental effect on male fertility.
Most of the global adult population own mobile phones, and around 14 per cent of couples in high and middle income countries have difficulty conceiving.
A team led by Dr Fiona Mathews, of the University of Exeter, conducted a systematic review of the findings from 10 studies, including 1,492 samples, with the aim of clarifying the potential role of this environmental exposure.
Participants in the studies were from fertility clinics and research centres and sperm quality was measured in three different ways: motility, viability and concentration.
In control groups, 50 to 85 per cent of sperm have normal movement. The researchers found this proportion fell by an average of 8 per cent when there was exposure to mobile phones.
Similar effects were seen for sperm viability. The effects on sperm concentration were less clear.
Dr Mathews said: "Given the enormous scale of mobile phone use around the world, the potential role of this environmental exposure needs to be clarified.
"This study strongly suggests that being exposed to radio-frequency electromagnetic radiation from carrying mobiles in trouser pockets negatively affects sperm quality.
"This could be particularly important for men already on the borderline of infertility, and further research is required to determine the full clinical implications for the general population."
The results were consistent across in vitro studies conducted under controlled conditions and observational in vivo studies conducted on men in the general population.
The findings, Effect Of Mobile Telephones On Sperm Quality: A Systematic Review And Meta-analysis, is published in the journal Environment International.