Abstract
PurposeIn previous studies, associations between breast-milk cortisol levels obtained on one occasion and infant neurodevelopment were demonstrated. However, more recent evidence indicates that breast-milk cortisol and cortisone concentrations follow the diurnal rhythm of maternal hypothalamus-pituitary-adrenal axis, peaking in the early morning and with a nadir at midnight. We studied associations between breast-milk glucocorticoid (GC) rhythmicity, and infant behavior and sleep.MethodsWe included 59 mothers, and their infants, of whom 17 had consulted an expert center during pregnancy for an increased risk of psychological distress. At 1 month postpartum, breast milk was sampled (on average six times) over a 24 h period for assessment of cortisol and cortisone using LC-MS/MS, and experienced maternal distress was assessed using the Hospital Anxiety and Depression Scale questionnaire. Three months after birth, infant behavior was assessed with the Infant Behavior Questionnaire, and infant sleep pattern was quantified by questionnaire. Associations between breast-milk GC rhythm parameters (maximum, delta, and Area Under the Curve increase and ground) and infant behavior and sleep were tested with linear regression analyses.ResultsNo consistent associations between breast-milk GC rhythm parameters and infant behavior or sleep were found.ConclusionsBreast-milk GC rhythmicity at 1 month postpartum was not associated with infant behavior or sleep at the age of 3 months. Findings from previous studies linking breast-milk cortisol to infant neurodevelopment might be biased by the lack of GC measurements across the full diurnal cycle, and should therefore be interpreted with caution.
Highlights
15% of pregnant women in Western countries are diagnosed with psychiatric conditions [1]
GC concentrations in their breast milk are displayed in Table 2, demonstrating that both cortisol and cortisone were highly dependent on collection time
With few exceptions, no associations were found between breast-milk GC rhythmicity at 1 month postpartum and infant behavior or sleep at age 3 months
Summary
15% of pregnant women in Western countries are diagnosed with psychiatric conditions [1]. Depressive and anxiety disorders are associated with alterations in hypothalamic-pituitary-adrenal (HPA-) axis activity, such as a lower morning peak or less diurnal variability in cortisol level [2, 3]. Fetal exposure to maternal depression or anxiety symptoms was associated with a more fearful temperament and disorganized sleep, along with a flattened cortisol rhythm, infancy [5,6,7]. Studies suggest that such effects may be mediated by increased fetal exposure to maternal GCs [8,9,10]. It has been proposed that non-nutritive bioactive compounds in breast milk might be involved in the development of sleep regulation in infants [16]
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