The Human Microbiome and Child Growth - First 1000 Days and Beyond.

The assembly of microbial communities within the gastrointestinal tract during early life plays a critical role in immune, endocrine, metabolic, and other host developmental pathways. Environmental insults during this period, such as food insecurity and infections, can disrupt this optimal microbial succession, which may contribute to lifelong and intergenerational deficits in growth and development. Here, we review the human microbiome in the first 1000 days - referring to the period from conception to 2 years of age - and using a developmental model, we examine the role of early microbial succession in growth and development. We propose that an 'undernourished' microbiome is intergenerational, thereby perpetuating growth impairments into successive generations. We also identify and discuss the intertwining host-microbe-environment interactions occurring prenatally and during early infancy, which may impair the trajectories of healthy growth and development, and explore their potential as novel microbial targets for intervention.