Associations between stress indicators and gut microbiota in pregnant women
The perinatal period has been linked with higher vulnerability to stress, depression, and anxiety, conditions that have adverse consequences for fetal and child neurodevelopment. The underlying mechanisms include the gut microbiota-brain axis, and recent research indicated significant associations between stress, depression, or anxiety and alterations in gut microbiota in pregnant women. Nevertheless, research in this avenue is still emerging, with existing studies being often limited by small sample sizes. We conducted a prospective longitudinal study of 171 women, collecting gut microbiota samples in each trimester of pregnancy and in the early postpartum, questionnaire data (perceived stress via the Perceived Stress Scale, symptoms of depression via the Edinburgh Postnatal Depression Scale, and anxiety via the 6-item State-Trait Anxiety Inventory) twice in each trimester and twice in the early postpartum period, and blood samples for cortisol levels analysis in the first and third pregnancy trimesters. Gut microbiota samples were analyzed by amplicon sequencing of 16S rRNA gene.  Perceived stress and symptoms of depression and anxiety showed moderate temporal changes and a high consistency at the individual level over the study period. Cortisol levels rose significantly from the first to the third trimester. There were significant temporal changes in microbiota composition between the first and second trimesters, and between the first and third trimesters. After controlling for false positive findings due to multiple testing, we found no significant associations between stress-related variables (perceived stress, cortisol levels, symptoms of depression and anxiety) and gut microbiota diversity, microbial community composition, or relative abundances of individual bacterial taxa.