The Vaginal Microbiome during Pregnancy in Health and Disease

Abstract

This study appraises the progress in the understanding of the composition of the vaginal microflora with a focus on the microbiome during pregnancy. This knowledge is presented with the background of the global health contribution, along with the importance of these microbial communities to pregnancy. A brief review of current methods employed to investigate the structure of these microbial populations is included. Two types of studies, cross-sectional and longitudinal, have been used to characterise the vaginal microbiota; both types are reviewed since they provide information that serves to piece together a more complete picture of the vaginal microflora and its changes during pregnancy. The identity of microbes present in the vagina are examined in the context of health and disease, and, more specifically, in the setting of pregnancy outcomes. The protective role of lactobacilli in maintaining a healthy vaginal environment is evaluated, with analyses of the different roles of various Lactobacillus spp. Classifications of the vaginal microbiota into vagitypes in non-pregnant and pregnant women are discussed. The associations of specific taxa with three adverse pregnancy results, namely, miscarriage, stillbirth, and preterm birth, are examined in some detail. Longitudinal studies investigating changes in the bacterial community composition and taxa abundance demonstrate that this microbiota decreases in richness and diversity relative to those present in non-pregnant microbiomes. Notwithstanding the significant effort made to characterise the vagina bacterial microbiota, a large number of issues remain to be fully understood.