Effect of the vaginal microbiome on the pregnancy rate in women receiving assisted reproductive treatment.

Purpose: To investigate if the vaginal microbiome influences the IVF outcome.

Methods: Thirty-one patients undergoing assisted reproductive treatment (ART) with own or donated gametes and with cryotransfer of a single euploid blastocyst were recruited for this cohort study. Two vaginal samples were taken during the embryo transfer procedure, just before transferring the embryo. The V3 V4 region of 16S rRNA was used to analyze the vaginal microbiome, and the bioinformatic analysis was performed using QIIME2, Bioconductor Phyloseq, and MicrobiomeAnalyst packages. Alpha diversity was compared between groups according to the result of the pregnancy test.

Results: Fourteen (45.2%) patients did not and seventeen (54.8 %) did achieve pregnancy under ART. A greater index of alpha diversity was found in patients who did not achieve pregnancy comparing to those who did, although this difference was not significant (p = 0.088). In the analysis of beta diversity, no statistically significant differences were observed between groups established as per the pregnancy status. Samples from women who achieved pregnancy showed a greater presence of Lactobacillus spp. The cluster analysis identified two main clusters: the first encompassed the genera Lactobacillus, Gardnerella, Clostridium, Staphylococcus, and Dialister, and the second included all other genera. Women who achieved pregnancy were mainly detected microorganisms from the first cluster.

Conclusions: The vaginal microbiome can influence the results of ART. The profiles dominated by Lactobacillus were associated with the achievement of pregnancy, and there was a relationship between the stability of the vaginal microbiome and the achievement of pregnancy.