The Uterus Sustains Stable Biological Clock during Pregnancy

The uterus and decidua exhibit circadian rhythms that may provide the fetus with important temporal information.

• Circadian rhythms of the key clock gene Period1 were observed in the pregnant rat uterus both during pregnancy and non-pregnancy.
• The uterus showed peak Per1-luc rhythms around dusk in both light-dark and constant darkness conditions.
• The decidua demonstrated circadian Per1 mRNA rhythms that peaked at night, but only during late pregnancy.
• The labyrinth, a fetal-originated tissue of the placenta, did not display circadian Per1 mRNA rhythms during pregnancy.
• These findings indicate that maternal reproductive organs may play a role in conveying circadian cues to the developing fetus.

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