Intrauterine Microbiota: Missing, or the Missing Link?

The intrauterine environment provides a key interface between the mother and the developing fetus during pregnancy, and is a target for investigating mechanisms of fetal programming. Studies have demonstrated an association between prenatal stress and neurodevelopmental disorders. The role of the intrauterine environment in mediating this effect is still being elucidated. In this review, we discuss emerging preclinical and clinical evidence suggesting the existence of microbial communities in utero. We also outline possible mechanisms of bacterial translocation to the intrauterine environment and immune responses to the presence of microbes or microbial components. Lastly, we overview the effects of intrauterine inflammation on neurodevelopment. We hypothesize that maternal gestational stress leads to disruptions in the maternal oral, gut, and vaginal microbiome that may lead to the translocation of bacteria to the intrauterine environment, eliciting an inflammatory response and resulting in deficits in neurodevelopment. The existence of an intrauterine microbiome in a healthy pregnancy is highly controversial. While several recent experiments have identified bacterial communities within the placenta and uterus, others indicate that such findings could be due to contamination. There is emerging evidence that the microbiota within the intrauterine environment may originate from the oral cavity, gut, or vagina. Maternal gestational stress has been associated with inflammation in utero. Intrauterine inflammation has been linked to detrimental neurodevelopmental outcomes, both structurally and functionally. [ABSTRACT FROM AUTHOR]