Investigating the effect of an abnormal cervico-vaginal and endometrial microbiome on assisted reproductive technologies: A systematic review

The female reproductive tract has an active microbiome, and it is suggested that these microbes could influence the outcome of assisted reproductive technologies (ART). This systematic review aimed to assess the vaginal/uterine microbiome, specifically with regard to improving the outcome of ART. English peer-reviewed journals were searched for studies investigating the vaginal/uterine micriobiome and female reproductive tract, using PRISMA guidelines. Twenty-six studies were included, 19 studying the vaginal and seven investigating the uterine microbiome. Studies using culture-based technologies found an abnormal vaginal microbiome AVM was not associated with ART outcome. However, studies using sequence-based technologies found an abnormal vaginal microbiome had a negative effect on ART. An abnormal uterine microbiome impacted ART outcome in all of the studies which used culture-based methods and the most extensive of the two studies using metagenomic sequencing. This review has revealed a lack of translational data relating an abnormal vaginal/uterine microbiome to ART outcomes, with inconsistencies between the results of the different studies. Therefore the nature of the relationship between the vaginal/uterine microbiome and fertility remains unknown. As we better characterize this relationship using modern metagenomic techniques, the potential to manipulate the female reproductive tract microbiome to improve ART could be a reality.