Impact of microbiota on female fertility and gynecological problems

The uterus was previously considered a sterile environment for embryo implantation and fetal growth; however, evidence showed that different microorganisms in the female reproductive tract may regulate human fertility. The Lactobacillus family is among the most prevalent bacteria in the vagina and uterus of the female reproductive system. Interestingly, a Lactobacillus-dominated (LD) uterine environment is associated with better pregnancy outcomes. Nevertheless, the mechanism by which an LD environment improves pregnancy outcomes is unknown. In the uterus, many commensal bacteria (eg, Bifidobacterium, Prevotella, Enterobacter, Streptococcus, and Staphylococcus) produce short-chain fatty acids (SCFAs), including acetate, butyrate, and propionate. SCFAs are crucial in modulating cytokine production (eg, IL-6 and IL-10) and immune cell populations (eg, T cells and macrophages) during embryo implantation and gynecological diseases. This minireview provides an overview of the roles of lactobacilli and SCFAs in female fertility and related diseases.