The who, how, and when of mother-infant microbial sharing.

Most strains shared between mothers and infants are gut-derived and can be observed into the second year of life, not vaginally derived strains.

• Why it matters: Understanding the sources and persistence of microbial sharing is crucial for insights into early-life health development. This knowledge gap limits our ability to influence microbiome establishment for better health outcomes.
• What they did: Mueller et al. analyzed microbial strains in mother-infant pairs, finding that the majority of shared strains originate from the gut and persist into the second year of life.
• The result: This indicates that gut-derived microbes play a dominant role in mother-infant microbial sharing, which may have implications for interventions aimed at shaping early microbiome development.