Bright bedrooms could be preventing women from getting pregnant, scientists say.
It is thought that night-time light from everything from street light creeping through the curtains to the eerie glow of tablet computers is playing havoc with the female reproductive cycle.
Middle-aged women may be particularly at risk.
The researchers advise those struggling to conceive to take simple measures to ensure a good night’s sleep. Tips include dimming the lights in the evening and having meals at regular times.
While the advice may seem odd, one in seven couples has trouble having a baby, and, in many cases, the cause is unknown.
Plus, there is growing concern that disruption to the body clock caused by artificial light is taking a heavy toll on health.
Cancer, diabetes, depression and obesity may all be fuelled by keeping the lights on at night.
British experts said link between fertility and general health should not be underestimated.
The US and Japanese researchers looked at how disrupting body clock of mice affected their fertility.
It had no effect on young mice – but pregnancy rates plummeted in middle-aged animals.
Some 71 per cent of older mice with normal body clocks got pregnant, compared to as few as 10 per cent of those whose internal, or circadian, rhythm had been disturbed, according to the journal Cell Reports.
Importantly, fertility could be restored by ensuring the creatures slept at a time in tune with their body clock.
