Mother-infant sharing of gut and vaginal microbes at the species and strain level (Sep 2026, n=68 dyads) "The dominant source of the shared microorganisms was the maternal gut microbiome at 33.7% compared to the maternal vaginal microbiome at 1.8%" Origins

[Michael Harrop]

https://medicalxpress.com/news/2026-10-mother-microbiome-baby-clues.html
https://www.cell.com/cell-reports/fulltext/S2211-1247(26)00998-8

If a mother has obesity, her child has a much higher risk of also having obesity. That's true of other metabolic and immune-mediated diseases, such as asthma and eczema, and the shared risk is not all attributable to genetics

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We found that the infant gut microbiome from 2 to 4 months of age shared about 35% of its species with the mother's gut or vaginal microbiome

The dominant source of the shared microorganisms was the maternal gut microbiome at 33.7% compared to the maternal vaginal microbiome at 1.8%. "We also found that infants that were born vaginally shared more species with their mother (38%) than infants that were born by C-section (24.7%)."

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Highlights​

• Vaginally delivered infants exhibited higher levels of species sharing
• Strain-level sharing frequency varied by species and delivery mode
• Vaginal Bifidobacterium was consistently shared with the infant gut

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Summary​

Mother-to-offspring microbial transmission is a foundational process for seeding the infant gut microbiome, yet the relative contributions of maternal body sites and the influence of birth delivery mode remain incompletely understood.

We use shotgun metagenomic sequencing in 68 mother-infant dyads to investigate species- and strain-level sharing of the maternal gut and vaginal microbiomes with the infant gut during the first year of life.

At 2–4 months of age, infants share an average of 35% of species with their mother’s microbiomes, with markedly greater sharing from the maternal gut than the vagina. Vaginally delivered infants exhibit higher levels of sharing than those born by cesarean section (C-section). Strain-level analyses reveal persistent mother-infant transmission across multiple Bacteroides and Bifidobacterium species genome bins, with strain-sharing frequencies varying by species and birth mode. C-section reduces the extent of mother-infant species- and strain-level sharing.

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