Microbiome in normal and pathological pregnancies: A literature overview.

This review summarizes recent findings on the changes that occur during pregnancy in the composition of the vaginal and gut microbiome and their association with metabolic, hormonal, and immunological factors. Despite many studies on the topic, the vaginal and gut microbial profiles and their influence on the course of pregnancy are still unclear. We present data suggesting that, contrary to traditional understanding, the placenta is not sterile but has a microbial community. We review and discuss new findings on changes in the richness and diversity of the microbiota of pregnant women with term or preterm births, obesity, and gestational diabetes mellitus. Several factors influence the bacterial profile of these women and may explain, at least in part, some of the discrepant findings between studies. The development of and access to new molecular biology methods and techniques has expanded the possibilities of research. This will contribute to a better understanding of the microbiome and its role in normal and pathological pregnancies.