New research indicates that maternal signals synchronize fetal circadian rhythms in utero, potentially influencing long-term neonatal healthcare outcomes.
RT’s Three Key Takeaways:
In Utero Synchronization: Researchers found that maternal signals help synchronize a fetus’s internal biological clock during the third trimester of pregnancy.
Hormonal Timing Signals: The study identified glucocorticoid hormones crossing the placenta as potential timing signals that align the fetal clock with the mother’s rest-activity cycle.
Clinical Implications: These findings suggest that the timing of synthetic steroid administration for preterm birth may influence the development of neonatal circadian rhythms.
Maternal signals play a critical role in setting the biological clock for infants while they are still in the womb, according to a study from Washington University in St. Louis. The research, published in the Journal of Biological Rhythms, identifies a specific developmental window where circadian rhythms begin to synchronize with local time.
Disruption of these rhythms during pregnancy is linked to an increased risk of mood disorders, including anxiety and depression, later in life.
“Understanding when the fetal clock begins to function helps us identify sensitive developmental windows when circadian disruption may have lasting effects and how those effects might be prevented or corrected,” said Nikhil Lokesh, study author and a research scientist in biology, in a news release.
Observing the Fetal Clock
To track these rhythms, scientists utilized genetically engineered mice to observe circadian clock activity in utero. By tagging a clock protein with a luminescent protein, researchers detected cyclical patterns of expression during the final week of pregnancy, which corresponds to the third trimester in humans.
The study found that these day-night rhythms synchronized to the mother’s rest-activity cycle before the fetus was capable of sensing light. The synchronization appears to coincide with the movement of glucocorticoid hormones across the placenta.
“Importantly, we found daily rhythms across the placenta from the mother to the baby before the fetus can sense light,” said Erik Herzog, professor in biology, in a news release.
Impact on Clinical Practice
These stress-related hormones naturally fluctuate throughout the day under the control of the mother’s internal clock. The researchers discovered that administering synthetic glucocorticoids—routinely given to patients at risk of preterm birth—accelerated the synchronization of daily rhythms in the offspring.
These findings may influence how and when clinicians administer medications to treat pregnancy conditions, as the time of day for hormone delivery could impact fetal development.
Circadian Health and Development
The researchers also observed a strong association between the failure to develop circadian clock gene activity in fetuses and a failure to deliver. While the study does not yet confirm if the absence of rhythms causes developmental problems, it suggests that clock activity is closely linked to healthy fetal development.
Lokesh noted that the findings highlight the importance of maintaining stable circadian rhythms during pregnancy, particularly as more than 80% of the world’s population is exposed to artificial light at night.
“This knowledge could help guide medical treatments, inform clinical practices, and shape public health policies aimed at protecting neonatal circadian health during pregnancy,” said Lokesh, study author and a research scientist in biology, in a news release.