||Chronic disease risk is inextricably linked to our early-life environment, where maternal, fetal, and childhood factors predict disease risk later in life. Currently, maternal obesity is a key predictor of childhood obesity and metabolic complications in adulthood. Although the mechanisms are unclear, new and emerging evidence points to our microbiome, where the bacterial composition of the gut modulates the weight gain and altered metabolism that drives obesity. Over the course of pregnancy, maternal bacterial load increases, and gut bacterial diversity changes and is influenced by pre-pregnancy- and pregnancy-related obesity. Alterations in the bacterial composition of the mother have been shown to affect the development and function of the gastrointestinal tract of her offspring. How these microbial shifts influence the maternal-fetal-infant relationship is a topic of hot debate. This paper will review the evidence linking nutrition, maternal obesity, the maternal gut microbiome, and fetal gut development, bringing together clinical observations in humans and experimental data from targeted animal models.