Maternal pre-pregnancy BMI influences breast milk composition, infant gut microbiome development, and early-life growth of term infants

Breast milk is the optimal nutrition for infants, yet individual variations in its composition and effects on infant growth remain unclear. This study examined human milk (HM) metabolome and microbiome dynamics in relation to infant growth and gut microbiome (GM) maturation in 164 exclusively breastfeeding Danish mother-infant dyads over the first three months. Results showed distinct temporal shifts in in HM metabolome and microbiome as well as infant GM composition. Maternal pre-pregnancy BMI correlated with HM metabolite profiles, infant growth, and GM diversity and composition. However, HM and GM maturity scores were not correlated, suggesting independent development. Notably, HM oligosaccharide clusters were linked to neonatal gut bacteria, including multiple Bifidobacterium spp. These findings indicate that maternal BMI may influence infant gut microbiome development and growth through changes in HM composition.