Vaginal Microbiome and Its Relationship with Assisted Reproduction: A Systematic Review and Meta-Analysis.

Area of Science:

• Reproductive Science
• Microbiome Research
• Clinical Obstetrics and Gynecology

Background:

• The vaginal microbiome composition is a critical determinant of reproductive outcomes in women undergoing assisted reproductive techniques (ART).
• Understanding the link between vaginal microbiota and ART success is essential for improving fertility treatments.

Purpose of the Study:

• To systematically review and meta-analyze evidence confirming that a favorable vaginal microbiome is associated with superior reproductive outcomes compared to an unfavorable microbiome.
• To identify specific microbial profiles, such as the abundance of Lactobacillus crispatus, that correlate with successful pregnancy.

Main Methods:

• A systematic review and meta-analysis of studies published within the last 10 years, using keywords such as "vaginal microbiome" and "reproduction" in PubMed and MEDLINE.
• Inclusion of 1735 records, categorizing participants into favorable and unfavorable vaginal microbiome groups.
• Bioinformatic analysis of a 56-woman cohort using multivariable association with linear models (MaAsLin2) for species-level taxonomic resolution.

Main Results:

• Women with a favorable vaginal microbiome exhibited significantly higher pregnancy rates (RR: 1.59) and live birth rates (RR: 1.41) compared to those with an unfavorable microbiome.
• A significantly lower rate of miscarriage was observed in women with a favorable microbiome (RR: 0.65).
• Bioinformatic analysis revealed that a high relative abundance of Lactobacillus crispatus was associated with a sixfold increase in the likelihood of pregnancy.

Conclusions:

• A favorable vaginal microbiome, characterized by a high abundance of Lactobacillus crispatus, is strongly linked to improved reproductive outcomes, including higher clinical pregnancy and live birth rates.
• The findings underscore the importance of the vaginal microbiome in ART success and suggest potential targets for therapeutic interventions.
• Despite the positive associations, the meta-analysis noted a low-quality bias in the included studies, warranting cautious interpretation.