Association Between Breastfeeding Intensity and Mammary Gland Involution Markers in Early Postpartum Among Women from Low-Income Households.

Background: The aim was to examine the associations between breastfeeding intensity and changes in concentrations of mammary gland involution markers (protein and lactose) among mothers participating in federal food assistance programs. Methods: Pregnant women in their third trimester who planned to breastfeed were recruited from local prenatal clinics (n = 25). After delivery, six weekly home visits were conducted to collect human milk samples and 24-hour infant feeding recalls. Milk protein and lactose concentrations were measured utilizing Bicinchoninic Acid and Megazyme assays, respectively. Bivariate tests were carried out using a statistical significance of p < 0.05. Results: Majority (84%) of our participants were either African American or of Latino origin. About one-fourth of our participants were primiparous and the average monthly household income was $3,150 with an average household size of 4. In week 2 postpartum, 18 mothers had a 100% breastfeeding intensity, while in week 6 it decreased to 16 mothers. A significant difference in milk protein concentration was seen between exclusive and mixed-feeding mothers from weeks 2 to 6; meanwhile, for lactose concentrations, the significant differences were seen only in weeks 3 and 4 (p < 0.005). Protein changes were negatively associated with breastfeeding intensity (as breastfeeding intensity went up, protein decreased), while lactose changes were positively associated with breastfeeding intensity (protein r = -0.5578; lactose r = 0.6571). Conclusions: Significant associations between intensity of breast milk feeding and mammary gland involution markers highlight the sensitivity of the mammary gland to mixed feedings in the early postpartum period.