Does the uterine microbiota affect the reproductive outcomes in women with recurrent implantation failures?

Abstract

Background Inefficiency of in vitro fertilization (IVF) programs can be caused by implantation failures. The uterine microbiota can influence the implantation process. However, it still remains unclear whether opportunistic microorganisms detected in the endometrium have a negative impact on the implantation success. The aim of our study was to evaluate the influence of the uterine microbiota on the embryo implantation success in patients undergoing assisted reproductive technologies. Methods The study included 130 women diagnosed with infertility. The patients were divided into three groups: group I included women with the first IVF attempt (n = 39); group II included patients with recurrent implantation failure following embryo transfer with ovarian stimulation (n = 27); group III consisted of women with recurrent implantation failure following frozen-thawed embryo transfer (n = 64). We performed microbiological examination of the embryo transfer catheter which was removed from the uterine cavity after embryo transfer; cervical discharge of all the patients was studied as well. Thirty patients were selected for metagenomic sequencing. Results The study showed that the uterine cavity is not free of microorganisms. A total of 44 species of microorganisms were detected: 26 species of opportunistic organisms and 18 species of commensals (14 species of lactobacilli and 4 species of bifidobacteria). Obligate anaerobic microorganisms and Gardnerella vaginalis were detected more frequently in group I compared to group III (strict anaerobes—15.4 and 1.6%; G. vaginalis—12.8 and 1.6%, respectively) (p < 0.05). However, this fact did not have a negative influence on the pregnancy rate: it was 51.3% in group I, it was 29.6% and 35.9% in women with recurrent implantation failures, respectively. Conclusion Opportunistic microorganisms which were revealed in low or moderate titers (103–105 CFU/ml) in the uterine cavity and cervical canal did not affect the pregnancy rate in the women in the study groups. The microflora of the uterine cavity and cervical canal differed in qualitative composition in 87.9% of patients, therefore, we can suggest that the uterine cavity may form its own microbiota. The microbiota of the uterine cavity is characterized by fewer species diversity compared to the microbiota of the cervical canal.

Deciphering the role of female reproductive tract microbiome in reproductive health: a review

“…Keburiya et al. demonstrated that L.crispatus in the cervix could produce lactic acid and antimicrobial compounds, inhibit inflammation, thereby reducing the incidence of human papilloma virus (HPV) infection ( Keburiya et al., 2022 ). Bacteroidetes is the second most abundant phylum, of which Prevotella is the dominant genus.…”

“…It has been found that among the cervical microbiome, Firmicutes is considered to be the most abundant phylum, and Lactobacillus is the main genus in this phylum (as high as 80.2%) (Onywera et al, 2019a;Onywera et al, 2019b). Keburiya et al demonstrated that L.crispatus in the cervix could produce lactic acid and antimicrobial compounds, inhibit inflammation, thereby reducing the incidence of human papilloma virus (HPV) infection (Keburiya et al, 2022). Bacteroidetes is the second most abundant phylum, of which Prevotella is the dominant genus.…”

A influência da microbiota endometrial na infertilidade: Uma revisão bibliográfica

“…Até a última década, o útero era considerado um órgão estéril, sendo mais frequentemente avaliada a presença de microrganismos relacionados a doenças infecciosas nesse sítio. O microbioma do trato genital feminino consistia, então, na análise da microbiota presente exclusivamente na vagina (KEBURIYA et al, 2022).…”