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Researchers indicates that infants whose cortisol levels are elevated during the latter stages of their maternal gestation may encounter difficulties in initiating sleep. Insights from sleep studies propose that evaluating cortisol levels during the third trimester could forecast the sleep behaviors of infants for a duration of up to seven months postpartum.

Disrupted sleep in babies linked to HPA system functioning

The University of Denver researchers suggest that disrupted sleep in babies could be connected to the functioning of their hypothalamic-adrenal-pituitary (HPA) system, which manages stress response. Cortisol, a product of the HPA axis, is associated with sleep disorders when the system is dysfunctional.

Cortisol, a steroid hormone produced by the adrenal glands, regulates metabolism, aids in stress response, possesses anti-inflammatory properties, regulates blood pressure, and influences the circadian rhythm. It’s often measured in fetal cortisol levels during late pregnancy using hair samples.

According to lead researcher Melissa Nevarez-Brewster, the rise in cortisol levels during pregnancy is natural and necessary for fetal development. However, elevated cortisol levels in late pregnancy might indicate potential sleep issues for the infant.

The study involved collecting hair cortisol samples from 70 newborns shortly after birth, with a majority being girls. At seven months old, parents filled out a sleep questionnaire detailing various aspects of their infants’ sleep patterns, alongside gathering information on gestational age at birth and family income.

High cortisol levels linked to longer sleep onset

Infants exhibiting elevated hair cortisol levels during the latter stages of pregnancy experienced prolonged sleep onset at seven months compared to counterparts with lower cortisol levels. The authors assert that these results establish a significant groundwork for investigating the enduring repercussions of fetal cortisol secretion on sleep well-being throughout infancy and early childhood. Additionally, further exploration could elucidate the mechanisms underlying infants’ transitions between sleep stages and the accrual of “sleep pressure” during the day, thereby influencing their nocturnal sleep latency.

Nevarez-Brewster suggests that the findings suggest potential prenatal impacts on early-life sleep health, highlighting the necessity for further exploration into the determinants fostering optimal sleep health from infancy onwards.