Researchers at Washington University in St. Louis have discovered that mothers play a crucial role in setting the biological clock of their fetuses while still in the womb. Using bioluminescent proteins, the study found that fetuses develop daily rhythms during the third trimester equivalent, synchronizing to the mother’s activity patterns via glucocorticoid hormones, which are associated with stress.
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The researchers employed genetically engineered mice that glowed when their circadian clock proteins were active, allowing them to observe real-time activity of the fetal biological clock. They noted that distinct day-night rhythms emerged in the developing pups during the last week of pregnancy, aligning with the mother’s cycle of rest and activity.
This synchronization occurred when the mother’s glucocorticoids started crossing the placenta, suggesting these hormones may serve as crucial time-setting signals for the fetus. The study also indicated that the administration of synthetic steroids, commonly given to pregnant women to prevent preterm birth, could accelerate this synchronization, potentially impacting neonatal health.
A noteworthy correlation was identified between disrupted circadian clock gene activity in fetuses and complications in delivery. This suggests that a properly functioning circadian rhythm in utero may be essential for healthy fetal development. Nikhil Lokesh, one of the study’s authors, emphasized the significance of maintaining stable circadian rhythms during pregnancy, as disruptions could heighten the risk of mood disorders in children later in life.
The findings highlight the importance of understanding the timing of hormonal fluctuations in pregnant individuals and could inform clinical practices regarding medication administration during pregnancy. The study was published in the Journal of Biological Rhythms and received funding from the National Institutes of Health and the March of Dimes Prematurity Research Center.