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Stress and mental health during pregnancy affect the oral microbiome
Last reviewed: 02.07.2025
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The amount and type of microbes in the saliva of pregnant women varies depending on whether they have life stressors, as well as symptoms of anxiety, depression and post-traumatic stress disorder (PTSD), according to a study published in the journal BMJ Mental Health.
Although previous studies have examined the link between the diversity of microbes in the gastrointestinal tract and stress, anxiety, and depression in pregnant women and new mothers, it has not yet been examined how the type and amount of microbes in the mouth (oral microbiome) are associated with maternal mental health.
Study design
The study included 224 pregnant women participating in the Michigan Prenatal Stress Study. They were assessed for recent stress and mental health symptoms during the second trimester of pregnancy. Participants provided saliva samples within a week of the assessment.
Key Results
Microbiome diversity:
- Women with high anxiety or depression had high alpha diversity in their oral microbiomes, meaning that their saliva contained many different types of microbes, each present in relatively equal proportions, with no one species dominating.
- Women with high PTSD symptoms had high beta diversity, indicating significant differences in the composition of microbes in their saliva, compared to women with low PTSD symptoms.
Association with specific types of microbes:
- Women who had experienced recent life stress had more species from the phylum Proteobacteria.
- Women with high depression had more species from the phylum Spirochaetes.
- In women with symptoms of anxiety and depression, an increase in Dialister species and species from the phylum Firmicutes was noted.
- Women with anxiety, depression, or PTSD were more likely to have species from the genus Eikenella.
Additional factors (covariates)
Twenty-two potential covariates that could influence microbiome changes were examined. These included:
- Smoking explained 7.2% of the variation in the oral microbiome.
- Dental problems - 3.1%.
- Intimate partner violence - 4.1%.
- Unplanned pregnancy - 2%.
Limitations of the study
The authors noted several limitations:
- There are insufficient data to analyze other potential covariates such as diet and body weight.
- The study focused on one time period during pregnancy.
- Anxiety and depression symptoms were assessed based on self-report, which may have affected the accuracy of the data.
- Possible sources of microbes, such as the gut or long-term oral health conditions, were not studied.
Conclusion
"Our study shows that multiple aspects of the oral microbiome in pregnant women are associated with life stress and mental health in women. Importantly, these associations differ from those reported in gut microbiome studies and studies in non-pregnant individuals," the authors concluded.
They add that their findings suggest the possibility of targeting the oral microbiome to improve psychological well-being during pregnancy.
Recommendations for future research
The authors suggest that the successful use of probiotics to improve mental health through effects on the gut microbiome could be extended to the oral microbiome. This could include:
- Change of diet.
- Recommendations for improving oral health.
- Probiotic therapies that could help mothers facing high levels of stress and poor mental health.