Impact of the Vaginal and Endometrial Microbiome Pattern on Assisted Reproduction Outcomes.

María Del Carmen Diaz-Martínez,Belén Moliner,Belén Lledó,Andrea Bernabeu,Adriana López-Pineda,Rauf Nouni-García,Juan Carlos Castillo,Vicente Ruiz,Concepción Carratalá-Munuera,Rafael Bernabeu,Adoración Rodríguez,Jose A Quesada,Jorge Ten,Ruth Morales,Joaquín Llácer,Francisca M Lozano

doi:10.3390/jcm10184063

María Del Carmen Diaz-Martínez, Belén Moliner + Show 14 more

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https://doi.org/10.3390/jcm10184063

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Abstract

Uterine microbiota may be involved in reproductive health and disease. This study aims to describe and compare the vaginal and endometrial microbiome patterns between women who became pregnant and women who did not after in vitro fertilization. We also compared the vaginal and endometrial microbiome patterns between women with and without a history of repeated implantation failures (RIF). This pilot prospective cohort study included 48 women presenting to the fertility clinic for IVF from May 2017 to May 2019. Women who achieved clinical pregnancy presented a greater relative abundance of Lactobacillus spp. in their vaginal samples than those who did not (97.69% versus 94.63%; p = 0.027. The alpha and beta diversity of vaginal and endometrial samples were not statistically different between pregnant and non-pregnant women. The Faith alpha diversity index in vaginal samples was lower in women with RIF than those without RIF (p = 0.027). The alpha diversity of the endometrial microbiome was significantly higher in women without RIF (p = 0.021). There were no significant differences in the vaginal and endometrial microbiomes between pregnant and non-pregnant women. The relative abundance of the genera in women with RIF was different from those without RIF. Statistically significant differences in the endometrial microbiome were found between women with and without RIF.

Highlights

Technological advances in mass sequencing have enabled the identification of different microbial communities in the uterine cavity, including in the vagina and the endometrial cavity [1]
We found some differences in relative abundance for the following species: L. helveticus, L. iners, L. gasseri, and L. jensenii (Figure 3)
Regarding the vaginal microbiome pattern in the samples collected during the secretory phase of the cycle, we found no differences in alpha diversity between women with and without history of repeated implantation failures (RIF) according to either the Shannon or Simpson alpha diversity indices (Figure 6a)

Summary

Introduction

Technological advances in mass sequencing have enabled the identification of different microbial communities in the uterine cavity, including in the vagina and the endometrial cavity [1]. Bacterial resident population in the uterus, and the existence of uterine microbiota might be reflective of bacterial tourists or invaders. The main bacteria at the vaginal and endometrial level belong to the genus Lactobacillus—producers of lactic acid that maintain the acidic pH of the vagina, which acts as a barrier against pathogens [3]. The live birth rate is correlated with the production of H2 O2 by Lactobacillus spp., and inversely correlated with the existence of bacterial vaginosis. Alterations to the vaginal flora—for example, due to bacterial vaginosis (provoked by Gardnerella vaginalis)—are associated with an increased risk of miscarriage [4,5]. Other pathogenic microorganisms—such as Chlamydia trachomatis, Neisseria gonorrhoeae, and Mycoplasma tuberculosis—may cause subclinical alterations related to risk factors for subfertility [6]

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