A mother’s gut bacteria could offer clues about her baby’s risk of developing eczema, according to recent research published in Nature that followed more than 700 families from pregnancy through the child’s first year.
The study also found that babies get much of their early gut bacteria from their mothers’ intestines, not primarily from breast milk or the vaginal microbiome.
Following bacteria from mother to baby
Researchers analyzed 4,526 stool samples from 714 mother–infant pairs and compared bacterial strains to identify which were shared between mothers and their children.
At both two and four weeks, infants shared a median of 65% of their gut bacterial strains with their mothers. By their first birthday, that figure had fallen to 25%.
The amount of a particular bacterium in the mother’s gut also mattered. Researchers reported that some strains were more abundant in the maternal gut.
“The clearest takeaway is that the maternal gut microbiome is the main reservoir seeding the infant gut, rather than the vaginal or breast milk microbiomes,” a Nestlé spokesperson told NutraIngredients.
The findings add to questions about how infants acquire beneficial gut bacteria. As previously reported in NI, recent research found that nearly one-third of infants in a Swedish cohort lacked detectable levels of Bifidobacterium, despite many being breastfed.
An unexpected connection with eczema
The researchers also examined whether the mother’s microbiome was associated with her child’s health.
Mothers whose babies developed eczema during their first year tended to have less diverse gut bacteria, and the association remained significant after the researchers accounted for smoking history and a family history of allergies.
A prediction model using the types of bacteria found in mothers around delivery showed moderate ability to distinguish between infants who developed eczema and those who did not.
“As this is the first report of such an association, replication in diverse populations and further exploration of causal pathways are needed,” the study authors wrote.
It is not yet clear why the mother’s microbiome might be linked to eczema. The researchers suggested that substances produced by gut bacteria during pregnancy could play a part in the developing immune system, but this remains a hypothesis.
“This is a promising and novel finding, but it is still at an early research stage and is not ready for use as a clinical tool,” the Nestlé spokesperson said.
Where maternal nutrition fits in
For companies developing probiotics, prebiotics and maternal nutrition products, the findings offer another reason to investigate the mother’s microbiome during pregnancy.
The study identified associations between maternal diet and the activity of certain bacteria in the infant gut. It also found that the mother’s gut microbiome was relatively stable during pregnancy, despite changes in the abundance of some bacterial species.
Birth method and feeding practices remained important influences on infant gut bacteria, with vaginal delivery and breastfeeding associated with greater sharing of maternal strains.
The role of feeding has also been explored in recent research, which found that milk-feeding type and the introduction of solid foods influenced how gut bacteria processed nutrients.
Whether dietary changes or supplements could increase the transfer of beneficial bacteria, or reduce eczema risk, is a separate question.
“The study supports a ‘maternal-first’ approach as a promising direction for future research, but the evidence is not yet sufficient,” the Nestlé spokesperson said. “It shows a clear biological link between the maternal and infant gut microbiomes, but it does not demonstrate that a maternal supplement will improve an infant’s health.”
The spokesperson identified clinical trials as the next priority, particularly studies examining which maternal bacteria reliably transfer to infants and whether nutrition can influence that process, and whether changes in gut bacteria lead to measurable improvements in infant health.
Source: Nature (2026), 658, 218–229. https://doi.org/10.1038/s41586-026-10922-9 “Maternal influences on infant gut microbiome and health.” Authors: T. Sinha et al.
