Linking Early Infant Growth With Milk-Derived Antibodies, Hormones, and Macronutrients During Exclusive Breastfeeding.

BACKGROUND: The relevance of exclusive breastfeeding to infant development is widely recognized. However, evidence linking the contents of specific milk components during lactation and infant growth is limited and sometimes controversial. RESEARCH AIMS: (a) To examine a set of nutritional and bioactive milk components at two time points during exclusive lactation, and their potential influence on child growth, in a well-defined cohort of Uruguayan mothers. (b) To analyze the association between the content of these components and the anthropometric growth parameters during the first year of life. METHODS: This observational study comprises 49 Uruguayan mother/child dyads. Macronutrients, cortisol, adiponectin, leptin, and antibodies were measured by ELISA in two sequential milk samples after 2.5 and 5.5 months post-delivery. The maternal perceived stress was self-reported using standardized questionnaires simultaneously. The core child's anthropometric growth parameters (body weight gain and weight-to-length ratio) were considered for simple and multivariable analysis. RESULTS: The levels of most milk components analyzed were similar between the two time points studied, and all of them were independent of the delivery type and infant sex. The prepregnancy BMI was positively correlated with the leptin content. The cortisol level was inversely correlated with infant growth at 6 months age and was significantly lower in the group of infants with overweight/obesity at this time. CONCLUSION: Maternal metabolic status influences leptin levels in mature milk, while cortisol content emerges as a key factor associated with infant growth during exclusive lactation, suggesting a potential protective effect against early overweight.