Daily rhythms generated by endogenous circadian mechanisms and synchronized to the light-dark cycle have been implicated in the timing of birth in a wide variety of species. Although chronodisruption (e.g., shift work or clock gene mutations) is associated with poor reproductive outcomes, little is known about circadian timing during pregnancy. This study tested whether daily rhythms change during full-term pregnancies in mice and women. We compared running wheel activity continuously in both nonpregnant ( n = 14) and pregnant ( n = 13) 12- to 24-week-old C57BL/6NJ mice. We also monitored wrist actigraphy in women ( N = 39) for 2 weeks before conception and then throughout pregnancy and measured daily times of sleep onset. We found that on the third day of pregnancy, mice shift their activity to an earlier time compared with nonpregnant dams. Their time of daily activity onset was maximally advanced by almost 4 h around day 7 of pregnancy and then shifted back to the nonpregnant state approximately 1 week before delivery. Mice also showed reduced levels of locomotor activity during their last week of pregnancy. Similarly, in women, the timing of sleep onset was earlier during the first and second trimesters (gestational weeks 4-13 and 14-27) than before pregnancy and returned to the prepregnant state during the third trimester (weeks 28 until delivery). Women also showed reduced levels of locomotor activity throughout pregnancy. These results indicate that pregnancy induces changes in daily rhythms, altering both time of onset and amount of activity. These changes are conserved between mice and women.

中文翻译：

---

怀孕会在小鼠和女性中引起较早的分型。

由内源性昼夜节律机制产生并与明暗周期同步的每日节律与多种物种的出生时间有关。尽管计时断裂（例如轮班工作或时钟基因突变）与不良的生殖结果有关，但对怀孕期间的昼夜节律时间知之甚少。这项研究测试了小鼠和妇女足月妊娠期间每日节律是否改变。我们比较了未怀孕（n = 14）和怀孕（n = 13）的12至24周龄C57BL / 6NJ小鼠的跑轮活动。我们还对受孕前两周（N = 39）的妇女（N = 39）进行腕部活动检查，然后在整个妊娠期间进行监测，并测量每天的睡眠发作时间。我们发现，在怀孕的第三天，与未怀孕的母鼠相比，小鼠的活动发生在更早的时间。在妊娠的第7天左右，他们的日常活动发作时间最多延长了将近4小时，然后在分娩前约1周转回到非妊娠状态。在怀孕的最后一周，小鼠的自发活动水平也降低了。同样，在女性中，早孕期和孕中期（妊娠第4-13和14-27周）的发作时间比怀孕前要早，孕晚期则要恢复到怀孕状态（直到分娩的第28周）。妇女在整个怀孕期间也表现出运动能力降低。这些结果表明，怀孕会导致每日节律发生变化，从而改变发病时间和活动量。这些变化在小鼠和女性之间是保守的。