PLoS ONE：频繁倒时差或影响生育

在一项最新研究中，科学家将刚刚交配成功的实验小鼠有规律地暴露在人造日光中。随后，每隔5到6天，研究人员便会把这些噬齿动物接触日光的时间往前调6个小时，这相当于从芝加哥乘飞机到伦敦要倒的时差。
 
在经过四次轮换之后，只有22%的受孕小鼠成功生产，而在对照组里，成功率达到了90%。
 
这些“鼠妈妈”也许已经将怀着的胎儿重新“吸收”掉了，或者是受精卵可能压根就没着床。5月24日，研究团队在《公共科学图书馆—综合》（PLoS ONE）上在线发表了此项成果。
 
该结果和之前的研究相符合。此前，研究人员发现，当调控小鼠生理周期的基因，即身体的“计时员”发生突变时，小鼠的发情周期会产生错乱，从而造成更多的怀孕失败。
 
同时，也曾有报道称，需要倒夜班的人和飞机上的乘务人员，其自身的生物钟被打乱后，流产和经期改变的次数会增加。
 
不过，要解决此问题，也许还有希望。
 
当小鼠的生物钟被往后拨而非向前调时，这种影响就没有那么严重了。因此，即使是生理节奏改变导致女性出现了生育问题，细心的安排可能会将这种紊乱限制到最低程度。

doi:10.1371/journal.pone.0037668
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Environmental Perturbation of the Circadian Clock Disrupts Pregnancy in the Mouse

Keith C. Summa1,2, Martha Hotz Vitaterna1, Fred W. Turek1,2

Background The circadian clock has been linked to reproduction at many levels in mammals. Epidemiological studies of female shift workers have reported increased rates of reproductive abnormalities and adverse pregnancy outcomes, although whether the cause is circadian disruption or another factor associated with shift work is unknown. Here we test whether environmental disruption of circadian rhythms, using repeated shifts of the light:dark (LD) cycle, adversely affects reproductive success in mice. Methodology/Principal Findings Young adult female C57BL/6J (B6) mice were paired with B6 males until copulation was verified by visual identification of vaginal plug formation. Females were then randomly assigned to one of three groups: control, phase-delay or phase-advance. Controls remained on a constant 12-hr light:12-hr dark cycle, whereas phase-delayed and phase-advanced mice were subjected to 6-hr delays or advances in the LD cycle every 5–6 days, respectively. The number of copulations resulting in term pregnancies was determined. Control females had a full-term pregnancy success rate of 90% (11/12), which fell to 50% (9/18; p<0.1) in the phase-delay group and 22% (4/18; p<0.01) in the phase-advance group. Conclusions/Significance Repeated shifting of the LD cycle, which disrupts endogenous circadian timekeeping, dramatically reduces pregnancy success in mice. Advances of the LD cycle have a greater negative impact on pregnancy outcomes and, in non-pregnant female mice, require longer for circadian re-entrainment, suggesting that the magnitude or duration of circadian misalignment may be related to the severity of the adverse impact on pregnancy. These results explicitly link disruptions of circadian entrainment to adverse pregnancy outcomes in mammals, which may have important implications for the reproductive health of female shift workers, women with circadian rhythm sleep disorders and/or women with disturbed circadian rhythms for other reasons.