The purpose of this novel, prospective cohort study was to assess the interrelationships between pro-inflammatory cytokines (TNF-α, IL-6), hormones (insulin, leptin) and PUFAs (n-6, n-3) in blood and breastmilk in early postpartum between women with normal BMI (Group 1, n = 18; 18.5<BMI≤24.9 kg/m2) and with overweight/obesity (Group 2, n = 15; BMI≥25.0 kg/m2) before pregnancy to determine if these components correlated to infant growth measures at age 4–8 weeks. This evidence concerns the gene INS and obesity due to melanocortin 4 receptor deficiency.