Maternal Milk Allopregnanolone May Buffer Negative Associations Between Maternal Postpartum Psychological Distress and Infant Regulatory Capacity

Maternal psychological distress during pregnancy and the early postpartum period is a risk factor for dysregulated affective and regulatory function in young infants. Animal models suggest that perinatal stress may alter offspring development via allopregnanolone (ALLO) exposure. For example, variations in placentally derived ALLO in preterm infants have been linked with altered fetal neurodevelopment. However, no studies have investigated naturalistic variations in ALLO concentrations in maternal milk as a potential moderator of associations between maternal distress and infant temperament during the postnatal period. The current study assesses associations among ALLO concentrations in human milk, maternal psychological distress, and infant temperament in 81 mother-infant dyads (31 females) measured at approximately 6.5 months postpartum (M = 6.55 months, range = 5.5-8 months). Results indicated that human milk ALLO concentration moderated effects of maternal psychological distress on infant regulatory capacity. Specifically, there was a negative association between maternal psychological distress and regulatory capacity in infants of mothers with below-mean ALLO concentrations, but not in infants of mothers with above-mean ALLO concentrations. However, there were no effects of ALLO on infant negative affect or surgency/positive affect. This study provides some of the first preliminary evidence that ALLO concentrations in human milk may moderate associations between maternal psychological distress and infant regulatory capacity.