ILSI Europe perspective review: site-specific microbiota changes during pregnancy associated with biological consequences and clinical outcomes: opportunities for probiotic interventions

Pregnancy induces notable alterations in the gut, vaginal, and oral microbiota driven by hormonal,immune, metabolic, dietary, and environmental factors. During pregnancy, the gut microbiota ischaracterized by increased proportions of the genus Bifidobacterium and the phylaPseudomonadota (formerly Proteobacteria) and Actinomycetota (formerly Actinobacteria). Thesechanges occur alongside reduced alpha diversity and greater beta diversity, changes that influencematernal metabolism and fetal development. Shifts in gut and oral microbiota have been asso-ciated with complications such as preterm birth (PTB), pre-eclampsia, and gestational diabetes(GDM), though patterns are sometimes inconsistent. The vaginal microbiota remains Lactobacillus-dominant during pregnancy, with reduced diversity leading to reduced risk of pathogenic infectionand increased diversity has been linked with a higher risk of PTB. Hormonal changes also affect theoral microbiota, potentially increasing pathogenic species and contributing to adverse outcomeslike PTB. Probiotic supplementation during pregnancy has significant potential to reduce adversepregnancy outcomes; however, clinical studies are still limited. Probiotics may be effective inalleviating maternal constipation and lead to lower PTB risk, particularly by modulating the vaginalmicrobiota, but they have limited impact on GDM. In the context of maternal mental health, somestudies suggest benefits of probiotics in reducing anxiety, but effects on depression are incon-clusive. This perspective examines how pregnancy-related microbial shifts, both natural andprobiotic-induced, affect maternal and fetal health and highlights potential opportunities for theinnovative use of probiotics during the gestation period.