The impact of vaginal and endometrial microbiota in women's fertility: a review of literature

The microbiome in health and human disease and its impact on human reproduction is becoming better characterized. The existence of a reproductive microbiota has highlighted the importance of a healthy microbiome in all the steps of reproduction, from gamete formation, to implantation, to labor, involving all the locations within the reproductive tract. Therefore, pathological shifts of these reproductive tract microbiota may be the cause or consequence of diseased conditions in women s health. In particular, the endometrial micro-biome seems to have an impact on embryo implantation and pregnancy maintenance, as an altered endometrial microbiome, characterized by a low abundance of Lactobacillus, has been associated with implantation failure and pregnancy loss. Endometrium is important to develop a healthy placenta and a physiologic pregnancy, so intrauterine infection can be the cause of reproductive complication. Healthy endometrial environment in ongoing pregnancy is important in both women undergoing IVF and woman wishing to conceive spontaneously. Different therapies are being investigated, such as specific pro-biotic and/or antibiotic therapies, drugs for the reduction of uterine peristalsis, and embryoendometrial synchronization during personalized embryo transfer. However, despite the promising findings reported, none of these options has clearly demonstrated a benefit.