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

Abstract

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.

Endometrial microbes and microbiome: Recent insights on the inflammatory and immune “players” of the human endometrium

“…However its possible applications in the clinical practice need to be further investigated. In this direction, in their recent systematic review, Bracewell‐Milnes et al could not find and correlation between vaginal/uterine microbiome and the outcome of assisted reproductive technologies.…”

More systematic reviews were registered in PROSPERO each year, but few records' status was up-to-date

“…Of the 76 SRs that reported being registered in PROS-PERO, one SR [17] did not report the registration number and we could not find the associated PROSPERO record by a manual search. Consequently, we could only assess 75 PROSPERO records (Table 4).…”

The vaginal microbiome in uterine transplantation

“…The structure of the VM has been shown to impact IVF outcomes, including clinical pregnancy rates, implantation rates, and livebirth rates, all of which are relevant in UTx, where the primary goal is the livebirth of a healthy infant. Vaginal dysbiosis or lactobacillus depletion is also implicated in both early and late miscarriage, and particularly in preterm birth .…”

“…The importance of the role of the vaginal microbiome (VM) in health is becoming increasingly recognised in obstetrics and gynaecology. The structure of the VM has been associated with in vitro fertilisation (IVF) outcome, miscarriage, and preterm labour . Given that UTx is a fertility‐restoring procedure, and each case can only be deemed successful once it has yielded a livebirth, the VM deserves particular consideration in the context of UTx.…”