Characterizations and psychoneuroimmunologic implications of secretory immunoglobulin A and cortisol in preterm and term breast milk.

This article combines data from two separate investigations. One study examined relationships between psychosocial factors and preterm milk immune variables. The other examined relationships between psychosocial and breastfeeding satisfaction factors and perceived milk sufficiency in term mothers. Milk samples were collected on the fifth postpartum day and frozen. Both studies collected data on anxiety, but other psychosocial variables differed. Mood states and social support were studied in preterm mothers, while breastfeeding satisfaction, milk maturation, and infant suckling characteristics were studied in term mothers. Milk samples were assayed for secretory immunoglobulin A (sIgA) and cortisol. sIgA and cortisol levels were higher in the milk from preterm mothers and were inversely related to each other in both preterm and term milk. In preterm mothers, anger and vigor were positively correlated with higher milk sIgA. The findings suggest that cortisol is present in milk and may potentially influence the secretion of milk sIgA. The relationships that were found when comparing psychosocial, dyadic, and stress factors with milk sIgA and cortisol are provocative and suggest new paradigms for studying lactation.