A Stress Reduction Intervention for Lactating Mothers Alters Maternal Gut, Breast Milk, and Infant Gut Microbiomes: Data from a Randomized Controlled Trial

Background: This study explored maternal gut, breast milk and infant gut microbiomes as possi-ble mediators of the observed effects of a relaxation intervention which reduced maternal stress and promoted infant weight gain. Methods: A randomized controlled trial was conducted in healthy Chinese primiparous mother-infant pairs. Mothers were randomly assigned to interven-tion group (IG, listening to relaxation meditation) or control group (CG). Outcomes were differ-ences in microbiome composition and diversity in maternal gut, breast milk and infant gut at 1- and 8-weeks between IG and CG, assessed by 16S rRNA gene amplicon sequencing of fecal and breastmilk samples. Results: 38 mother-infant pairs were included in this analysis (IG=19, CG=19). Overall microbiome community structure in the maternal gut was significantly different between IG and CG at 1-week and the difference was more significant at 8 weeks (Bray-Curtis distance R2=0.04 vs. R2=0.13). Post-intervention, the α-diversity was significantly lower in IG breast milk (observed features: CG=295 vs. IG=255, p=0.032); the Bifidobacterium genera presented higher relative abundance. In parallel, significantly higher α-diversity was observed in IG infant gut (observed features: CG=73 vs. IG=113, p