What happens when you give a mouse jet lag? If she's pregnant, the results could be disastrous. In a new study, researchers placed laboratory mice that had
recently copulated on a regimen of artificial daylight. Then they shifted the rodents' exposure to this light forward by 6 hours every 5 to 6 days—the
equivalent of flying from Chicago to London. Four time shifts later, only 22% of the mice gave birth, compared with 90% in a control
group. Mothers may have reabsorbed their pregnancies, or fertilized eggs might never have implanted, the team reports online today in PLoS ONE.
The result fits with previous studies which found that mice with mutations in genes that regulate their circadian rhythms, the body's timekeeper, have
irregular estrous cycles and more pregnancy failures. Shift workers and flight attendants, whose own body clocks are disrupted, also report increased
miscarriages and menstrual changes. But there may be hope. When mice were clock-shifted backward rather than forward, the effect was less severe. So even
if circadian changes lead to fertility problems in women, careful scheduling might limit the turbulence.
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