Your Vaginal Microbiome May Be Inherited From Your Mother, Genomic Study Finds

If you have ever wondered why your body seems to run on the same bacterial "settings" as your mother's, a new genomic study on the vaginal microbiome offers some of the most direct evidence yet that this is real, and traceable down to the exact bacterial strain. Researchers who built their study on Belgium's citizen-science Isala project sequenced the vaginal microbiomes of mothers and their adult daughters and found genetic matches specific enough to rule out coincidence. For anyone who has ever dealt with recurring bacterial vaginosis (BV) or wondered why some vaginal infections seem to "run in the family," this is the first strain-level look at how that pattern might actually take root.

Key takeaways:

• Daughters' vaginal microbiomes are significantly more similar to their own mother's than to an unrelated mother's, and in some pairs the daughter carries the exact same bacterial strain as her mother, matched down to the genome.
• A daughter's odds of having a Lactobacillus crispatus-dominant vaginal microbiome (a bacterial pattern linked to lower infection risk) jump sharply when her mother has the same pattern.
• The strongest matches persisted even when mothers were decades past menopause, suggesting these strains can be carried for a very long time once established.
• The study cannot say whether the bacteria are passed at birth, absorbed later through shared living space, or shaped by shared genetics; it only shows that the match is real.

Vaginal Microbiome Strains Match Between Mothers and Daughters

The core finding is that daughters' vaginal bacterial communities look statistically like a genetic echo of their mothers', not just a broad regional resemblance. Working within the Isala citizen-science program, a large ongoing effort out of the University of Antwerp that has sequenced vaginal samples from thousands of women, the researchers identified 35 mother-daughter pairs (62 women total) willing to participate together. In a metagenomic analysis of 23 of those daughters and 19 of their mothers, daughters shared an average of 48.3% species-level similarity with their own mother's vaginal microbiome, compared with only 31.8% similarity to a randomly assigned, unrelated mother. That gap held up across 10,000 random reshufflings of the data (p = 0.0008), which is the statistical equivalent of the researchers repeatedly trying to explain the pattern away by chance and failing every time.

The species driving much of that overlap is Lactobacillus crispatus, a bacterium widely considered a marker of a "healthy" vaginal microbiome because it produces protective lactic acid. When a mother's vaginal microbiome was dominated by L. crispatus (making up roughly 30% or more of her bacterial community), her daughter's odds of also being L. crispatus-dominant jumped by a factor of 21 (p < 0.01). Statistically, maternal L. crispatus dominance alone explained about 41% of the variation in which species ended up dominating the daughter's own vaginal microbiome, a large share for a single predictor in biology.

Why Vaginal Bacteria Matter for Conditions Like BV

This matters most directly for anyone who deals with bacterial vaginosis, a common condition where protective Lactobacillus species are crowded out by a more mixed, less protective bacterial community, often causing odor, discharge and discomfort, and raising the risk of other infections. Lactobacillus species, and L. crispatus in particular, are known to suppress the growth of BV-associated bacteria by producing lactic acid and antimicrobial compounds. If a mother's vaginal microbiome tends toward the protective, L. crispatus-dominant pattern, this study suggests her daughter is statistically more likely to start out with that same protective pattern too, and the reverse may also hold for less protective, BV-associated bacterial communities. That is relevant for anyone who has noticed that recurring vaginal infections, or a lack of them, seem to track within their family.

How Researchers Tracked Bacterial Strains Across Generations

What sets this study apart methodologically is that it did not stop at "which species are present." The team went a level deeper, comparing whole genomes of individual bacterial strains to see whether mothers and daughters carried literally the same lineage of bacteria, not just the same species. Using metagenomic sequencing plus targeted culturing of L. crispatus, followed by whole-genome sequencing of the resulting isolates, the researchers generated 21 representative bacterial genomes from 18 participants and compared them using a strict similarity threshold (99.99% genome identity). Among the 12 mother-daughter pairs where both mother and daughter were L. crispatus-dominant, 6 pairs, or half, were sharing a detectably identical strain. The cohort's ages ranged from 18 to 32 for daughters and 45 to 68 for mothers, with 63.2% of mothers postmenopausal at the time of sampling, and the researchers cross-checked their species-level pattern against a second, independent dataset of 47 vaginal metagenomes from Black and American mother-daughter pairs, originally collected for an unrelated douching-intervention study, which confirmed that daughters were significantly more similar to their own mothers there too (p < 0.0001).

What This Could Mean for Your Own Vaginal Health

For someone trying to understand their own recurring vaginal health issues, the practical takeaway is not that anything is fixed by genetics, but that family history may be a genuinely useful clue. If your mother has dealt with frequent BV or a "difficult" vaginal microbiome, this study offers a biological reason your own microbiome might trend the same way, beyond shared bathroom habits or diet. That said, this is not grounds to try to intentionally "inherit" a healthier microbiome through home remedies or unproven supplements. Live biotherapeutic products containing L. crispatus strains are being tested in clinical trials for BV, but nothing here validates any over-the-counter probiotic, vaginal supplement, or DIY intervention as a way to reshape your own strain composition.

The Open Question: Birth, Environment, or Genetics

The biggest limitation is that this study cannot pin down how the bacteria actually get passed along. It is observational, comparing existing microbiomes in adult pairs rather than tracking transmission as it happens, so it cannot experimentally prove a cause. The researchers found that measurable lifestyle and behavioral factors, like current cohabitation, explained only about 10.4% of the similarity between mothers and daughters, which points to something else, potentially transmission at birth, shared household environment over years, or host genetics, doing most of the work. Interestingly, three of the six strain-sharing pairs involved postmenopausal mothers aged 46 to 68, and the amount of genetic drift in the shared strains did not correlate with the daughter's age, hinting that these strains, once established, can persist largely unchanged for decades. The second validation cohort also complicates a clean birth-transmission story: it showed less rather than more strain sharing within families compared with outside them, and that cohort had a higher rate of BV-associated microbiomes, so the strain-level transmission signal may depend on which vaginal bacterial community a person has to begin with.

Isala's Global Expansion Could Answer What Comes Next

The Isala program that supplied the core dataset for this study started as a Belgian citizen-science effort and has since grown into what researchers are calling the "Isala Sisterhood," with regional versions launching in roughly 10 more countries. Larger, more geographically diverse versions of this mother-daughter comparison, especially ones that could sample women shortly after birth rather than decades later, would help settle whether birth itself is the key transmission moment or whether it is more about years of shared environment. The authors frame this as a first step toward understanding how a "healthy" vaginal microbiome establishes itself generation to generation, which matters for future probiotic and biotherapeutic development.

Common Questions

Is the vaginal microbiome inherited like DNA? Not in the same way. DNA is passed through genes at conception; this study shows bacterial strains can be shared between mothers and daughters, but the mechanism (birth exposure, shared environment, or genetics shaping a favorable habitat) is not yet established.

Does this mean vaginal bacteria are definitely passed during childbirth? Not necessarily. The study looked at existing adult microbiomes rather than tracking transmission at the moment of birth, so it cannot distinguish birth-time transmission from years of later exposure through shared living space.

Could this research lead to new treatments for bacterial vaginosis? Possibly, in the long run. Understanding how protective strains like L. crispatus establish and persist across generations could inform future live biotherapeutic products, but no such treatment is validated by this study itself.

Does a similar pattern show up in the gut microbiome? This study focused specifically on the vaginal microbiome, not the gut. Other research has looked at mother-infant gut microbiome sharing, but the transmission dynamics and relevant bacterial species differ between the two body sites.

References

1. Maria Pinedo-Bardales, Isabel Erreygers, Camille Nina Allonsius, et al. (2026). Species and strain sharing in the vaginal microbiome of mothers and their adult daughters. Cell Reports. https://doi.org/10.1016/j.celrep.2026.117942
2. Sarah Lebeer, Sarah Ahannach, Thies Gehrmann, et al. (2023). A citizen-science-enabled catalogue of the vaginal microbiome and associated factors. Nature Microbiology. https://doi.org/10.1038/s41564-023-01500-0
3. Fabrice Atassi, Diane L. Pho Viet Ahn, Vanessa Lievin-Le Moal (2019). Diverse Expression of Antimicrobial Activities Against Bacterial Vaginosis and Urinary Tract Infection Pathogens by Cervicovaginal Microbiota Strains of Lactobacillus gasseri and Lactobacillus crispatus. Frontiers in Microbiology. https://doi.org/10.3389/fmicb.2019.02900
4. M. France, S. Brown, A. Rompalo, R. M. Brotman, J. Ravel (2021). Identification of shared bacterial strains in the vaginal microbiota of reproductive-age mothers and daughters using genome-resolved metagenomics. https://doi.org/10.1101/2021.11.16.468914
5. These scientists have a plan to demystify the vaginal microbiome. Science News. https://www.sciencenews.org/article/vaginal-microbiome-citizen-science