Maternal stress is associated with oral microbiota diversity patterns in pregnant women in Quito, Ecuador

Background: Psychological stress is present in almost all pregnancies and contributes to maternal and fetal physiology. Human microbiota is dynamic and highly responsive to maternal stress. Aims: To characterize maternal stress levels and their association with oral microbiota diversity patterns in pregnant women attending a public hospital in Quito, Ecuador. Methods: Pregnant women were recruited at a public hospital upon presentation for labor. Stress levels were assessed using the 13-item Perceived Stress Scale. Oral mucosa samples were collected before the mothers entered the delivery room. The V3–V4 region of the 16S rRNA gene, from the extracted DNA of the samples, was sequenced using the Illumina MiSeq® platform. Alpha and beta diversity were evaluated using Shannon, Faith's PD, and weighted UniFrac metrics. Group differences were tested with PERMANOVA and Kruskal–Wallis tests (p < 0.05). Results: Fifty-six women were included, with low (35.7%), moderate (50.0%), and very high (14.3%) perceived stress levels. Alpha diversity was greater in the very high-perceived stress group compared with low and moderate groups (Shannon 4.58 vs. 3.85 and 3.99; p = 0.01–0.04; Faith 5.15 vs. 4.17 and 4.43; p = 0.01–0.02). Patescibacteria and Bacillota (Firmicutes) were depleted in highly stressed women. Beta diversity showed no differences. Conclusion: Maternal stress was associated with increased oral alpha diversity, primarily driven by changes in community evenness, without significant shifts in beta diversity.