FIGURE 2.

Evolution of the early-life gut microbiota and events influencing its composition. Factors such as the maternal microbiota, delivery mode, gestation time, and type of feeding strongly influence the microbiota. Colonization and expansion of the gut microbiota, shaped by diet, results in the establishment of an adult-like microbiota around 2–3 y of age, with firmicutes and bacteroidetes as the predominant phyla. Early life is a susceptible period when modifications in the gut microbiota composition can have long-term effects on health (5, 22).