The Association between Vaginal Dysbiosis and Reproductive Outcomes in Sub-Fertile Women Undergoing IVF-Treatment: A Systematic PRISMA Review and Meta-Analysis

All Properties of Infertility Microbiome in a Review Article

BACKGROUND

The microbiome is crucial for many physiological processes, including immunity, metabolism, and reproduction.

AIMS

This review aims to contribute to a detailed understanding of the microbiome of the genital tract, which can lead to better management of dysbiosis and reproductive disorders.

METHODS

Data from the four international information databases Medline, Scopus, Embase, and Google Scholar. The search strategy was based on the combination of the following terms: "microbiota," "microbiome," "microfilm," "microflora," "fertility," or "infertility."

RESULT

The advent of next-generation sequencing-based technologies during the last decade has revealed the presence of microbial communities in nearly every part of the human body, including the reproductive system. Several studies have shown significant differences between the microbiota of the vagina and endometrium, as well as other parts of the upper genital tract.

DISCUSSION

The human microbiome plays a critical role in determining a person's health state, and the microbiome of the genital tract may impact fertility potential before and after assisted reproductive treatments (ARTs).

CONCLUSION

To completely understand the role of the microbiome, future research should focus not only on the description of microbiota but also on the interaction between bacteria, the production of biofilms, and the interaction of microorganisms with human cells.

Understanding the Burden and Management of Urinary Tract Infections in Women

Urinary tract infections (UTIs) represent a prevalent health concern among the female population, with anatomical and physiological determinants such as a shorter urethra and its proximity to the rectum augmenting vulnerability. The presence of Escherichia coli and various other pathogens plays a significant role in the etiology of these infections, which can be aggravated by sexual intercourse and disturbances to the vaginal microbiome. The physiological alterations associated with pregnancy further elevate the likelihood of UTIs, with untreated cases potentially leading to severe complications such as pyelonephritis, preterm labor, and stillbirth. Furthermore, postmenopausal women encounter an augmented risk of UTIs attributable to estrogen deficiency and vaginal atrophy, as well as conditions including pelvic organ prolapse (POP) and urinary incontinence (UI), which hinder optimal bladder functionality. The aforementioned factors, in conjunction with the rising prevalence of cesarean deliveries and catheterization, complicate the management of UTIs. While precise diagnosis is paramount, it remains a formidable challenge, notwithstanding advancements in molecular diagnostic techniques. Management strategies encompass antibiotic-sparing therapies; however, the increasing incidence of multidrug resistance represents an alarming trend. Diverse guidelines from various medical specialties endeavor to standardize treatment approaches, yet significant inconsistencies continue to exist. This study systematically appraises the extant guidelines, evaluating the quality of evidence while identifying areas of agreement and discord to supply practitioners with effective strategies for UTI management.

The impact of caesarean scar niche on fertility - a systematic review

BACKGROUND

The trend of increasing caesarean section (CS) rates brings up questions related to subfertility. Research regarding the influence of CS on assisted reproduction techniques (ART) is conflicting. A potential mechanism behind CS-induced subfertility is intra uterine fluid resulting from a caesarean scar defect or niche. The vaginal microbiome has been repeatedly connected to negative ART outcomes, but it is unknown if the microbiome is changed in relation to a niche.

METHODS

This systematic review describes literature investigating the effect of a niche on live birth rates after assisted reproduction. Furthermore, studies investigating a difference in microbial composition in subfertile persons with a niche compared to no niche are evaluated. Pubmed, Embase and Web of Science were searched on March 2023 for comparative studies on both study questions. Inclusion criteria were i.e., English language, human-only studies, availability of the full article and presence of comparative pregnancy data on a niche. The quality of the included studies and their risk of bias were assessed using the Newcastle-Ottawa scale for cohort studies. The results were graphically displayed in a forest plot.

RESULTS

Six retrospective cohort studies could be included on fertility outcomes, with a total of 1083 persons with a niche and 3987 without a niche. The overall direction of effect shows a negative impact of a niche on the live birth rate (pooled aOR 0.58, 95% CI 0.48-0.69) with low-grade evidence. Three studies comparing the microbiome between persons with and without a CS could be identified.

CONCLUSION

There is low-grade evidence to conclude that the presence of a niche reduces live birth rates when compared to persons without a niche. The theory that a caesarean has a negative impact on pregnancy outcomes because of dysbiosis promoted by the niche is interesting, but there is no sufficient literature about this.

Cervicovaginal and gastrointestinal microbiomes in gynecological cancers and their roles in therapeutic intervention

Cancer remains a significant global health concern, and understanding factors that regulate cancer development is important. The microbiome, with its potential role in cancer development, progression, and treatment, has garnered increasing attention in recent years. The cervicovaginal and gastrointestinal microbiomes in females constitute complex biological ecosystems. Although the gut microbiome has been extensively studied, little is known about the cervicovaginal microbiome. The microbiome plays a crucial role in maintaining local microenvironments and tissue homeostasis, but dysbiosis can disrupt this fine balance and contribute to pathological ramifications leading to cancer. This review explores the current understanding of the microbiome's correlation with gynecological cancers and highlights the potential of microbiome-based interventions to improve outcomes in these cancers. In addition, this review underscores the gaps and limitations in the literature, such as findings in specific ethnicities compared with understudied ethnicities. In addition, discrepancies in molecular techniques and terminology (microbiome vs. microbiota) used in the literature are addressed. Emerging evidence linking gynecological cancers and dysbiosis underscores microbiota as a potential target for cancer prevention and therapy. Manipulating the microbiome, such as through the use of probiotics, prebiotics, antibiotics, or vaginal and fecal transplantation, has demonstrated benefits in the treatment of chronic and inflammatory conditions. Further translational research in this field is needed to integrate the benefits of beneficial microorganisms in the fight against gynecological cancers.

A Metagenomics Pipeline to Characterize Self-Collected Vaginal Microbiome Samples

Vaginitis is a widespread issue for women worldwide, yet current diagnostic tools are lacking. Bacterial vaginosis (BV) is the most prevalent type of vaginitis, found in 10-50% of reproductive-aged women. Current diagnostic methods for BV rely on clinical criteria, microscopy, or the detection of a few microbes by qPCR. However, many vaginal infections lack a single etiological agent and are characterized by changes in the vaginal microbiome community structure (e.g., BV is defined as a loss of protective lactobacilli resulting in an overgrowth of anaerobic bacteria). Shotgun metagenomic sequencing provides a comprehensive view of all the organisms present in the vaginal microbiome (VMB), allowing for a better understanding of all potential etiologies. Here, we describe a robust VMB metagenomics sequencing test with a sensitivity of 93.1%, a specificity of 90%, a negative predictive value of 93.4%, and a positive predictive value of 89.6% certified by Clinical Laboratory Improvement Amendments (CLIA), the College of American Pathologist (CAP), and the Clinical Laboratory Evaluation Program (CLEP). We sequenced over 7000 human vaginal samples with this pipeline and described general findings and comparisons to US census data.

Testing on bacterial vaginosis in a subfertile population and time to pregnancy: a prospective cohort study

PURPOSE

This study aimed to investigate the influence of bacterial vaginosis on time to pregnancy in subfertile couples.

METHODS

Couples attending a teaching hospital in the Netherlands having an initial fertility assessment (IFA) between July 2019 and June 2022 were included in this prospective study, with follow-up of pregnancies until June 2023. Vaginal samples at IFA were analyzed on pH, qPCR BV, and 16S rRNA gene microbiome analysis of V1-V2 region. Main outcome measures were time from initial fertility assessment to ongoing pregnancy at 12 weeks and live birth, analyzed by Kaplan-Meier and Cox regression with adjustment for potential confounders.

RESULTS

At IFA, 27% of 163 included participants tested positive for BV. BV status had no influence on time to ongoing pregnancy (HR 0.98, 0.60-1.61, aHR 0.97, 0.58-1.62). In persons with unexplained subfertility, positive BV status had a tendency of longer time to pregnancy. When persons had an indication for fertility treatment, positive BV status (HR 0.21, 0.05-0.88, aHR 0.19, 0.04-0.85) and microbiome community state type III and type IV had significant longer time to pregnancy.

CONCLUSION

This study indicates that BV may have a potential negative impact on time to live birth pregnancy in subfertile persons with an indication for fertility treatment. This study did not find an association between BV and time to live birth pregnancy in a general group of subfertile couples or in unexplained subfertility. More research should be done in persons with unexplained subfertility and if treatment improves time to pregnancy.

Vaginal dysbiosis - the association with reproductive outcomes in IVF patients: a systematic review and meta-analysis

PURPOSE OF REVIEW

To examine impact of vaginal dysbiosis (VD), including bacterial vaginosis (BV) and aerobic vaginitis (AV) on reproductive outcomes of in vitro fertilization (IVF) patients.

RECENT FINDINGS

BV-bacteria (e.g. Gardnerella ) and AV-bacteria (e.g. Streptococci and Enterococci ) have been identified in the endometrium. However, there is inconclusive evidence whether IVF patients with VD have lower success rates.

SUMMARY

The present systematic review and meta-analysis of PubMed/Medline, until December 2023 included 25 studies, involving 6835 IVF patients. Overall VD was defined as an approximation of community state type IV, including BV and AV-type dysbiosis based on either molecular or microscopy methods. Outcomes were live birth rate (LBR), early pregnancy loss (EPL), clinical pregnancy rate (CPR), and biochemical pregnancy rate (BPR).Vaginal dysbiosis prevalence was 19% [1271/6835, 95% confidence interval (CI) 18-20%]. Six studies examined AV-type dysbiosis with a prevalence of 4% (26/628, 95% CI 3-6%). Vaginal dysbiosis correlates with a higher EPL [relative risk (RR) = 1.49, 95% CI 1.15-1.94] and lower CPR (RR = 0.82, 95% CI 0.70-0.95). No statistically significant impact of VD, BV, or AV was found on LBR and BPR.Thus, the association between VD and reproductive outcome remains puzzling as it is difficult to explain how VD impacts CPR and EPL but not LBR and BPR.

Bacterial vaginosis in a subfertile population undergoing fertility treatments: a prospective cohort study

PURPOSE

This study investigates the role of bacterial vaginosis (BV) on pregnancy rates during various fertility treatments. BV is known to influence several obstetric outcomes, such as preterm delivery and endometritis. Only few studies investigated the effect of BV in subfertile women, and studies found a negative effect on fecundity especially in the in vitro fertilisation population.

METHODS

Observational prospective study, 76 couples attending a fertility clinic in the Netherlands between July 2019 and June 2022, undergoing a total of 133 attempts of intra uterine insemination, in vitro fertilization or intra cytoplasmatic sperm injection. Vaginal samples taken at oocyte retrieval or insemination were analysed on qPCR BV and 16S rRNA gene microbiota analysis of V1-V2 region. Logistic regression with a Generalized Estimated Equations analysis was used to account for multiple observations per couples.

RESULTS

A total of 26% of the 133 samples tested positive for BV. No significant differences were observed in ongoing pregnancy or live birth rates based on BV status (OR 0.50 (0.16-1.59), aOR 0.32 (0.09-1.23)) or microbiome community state type. There was a tendency of more miscarriages based on positive BV status (OR 4.22 (1.10-16.21), aOR 4.28 (0.65-28.11)) or community state type group III and IV. On baseline qPCR positive participants had significantly higher body mass index and smoked more often. Odds ratios were adjusted for smoking status, body mass index, and socioeconomic status.

CONCLUSION

Bacterial vaginosis does not significantly impact ongoing pregnancy rates but could affect miscarriage rates.

Clinical Relevance of Vaginal and Endometrial Microbiome Investigation in Women with Repeated Implantation Failure and Recurrent Pregnancy Loss

Recent studies have investigated if and how the vaginal and endometrial microbiome might affect endometrial receptivity and reproductive health. Although there is no consensus on the existence of a core uterine microbiome yet, evidence shows that the dominance of Lactobacillus spp. in the female reproductive tract is generally associated with eubiosis and improved chances of successful implantation and an ongoing pregnancy. Conversely, vaginal and endometrial dysbiosis can cause local inflammation and an increase of pro-inflammatory cytokines, compromising the integrity and receptivity of the endometrial mucosa and potentially hampering successful embryonic implantation. This review provides a critical appraisal of the influence of the vaginal and endometrial microbiome as parts of the female reproductive tract on fertility outcomes, focusing on repeated implantation failure (RIF) and recurrent pregnancy loss (RPL). It seems that RIF as well as RPL are both associated with an increase in microbiome diversity and a loss of Lactobacillus dominance in the lower female reproductive system.

Vaginal Microbiota Molecular Profiling in Women with Bacterial Vaginosis: A Novel Diagnostic Tool

Bacterial vaginosis (BV) is a most common microbiological syndrome. Multiplex next-generation sequencing (NGS) or molecular tests allow a complete and accurate vaginal microbiota profiling in order to determine the primary causative agent. Due to the high costs and limited availability of NGS, the multiplex real-time PCR draws more attention. The present study aimed to evaluate the microbial composition and dominant lactobacilli species in non-pregnant women with bacterial vaginosis using a multiplex RT-PCR test and determine its diagnostic significance. In total, 331 women complaining of vaginal discharge were included. BV was confirmed upon clinical examination and Nugent criteria. A real-time PCR test was carried out with a new Femoflor test, which identifies opportunistic bacteria, STD pathogens, and some viruses. According to the results, the rate of lactobacilli is significantly reduced in BV-affected patients when compared to healthy women. Moreover, the rate of L. crispatus significantly decreases, while the rate of L. iners remains high. Among obligate anaerobic bacteria, Gardnerella vaginalis was the most prevalent in women with BV. The Femoflor test demonstrated high sensitivity and specificity for diagnosing BV. Moreover, the test allows the identification of infection in women with intermediate vaginal microbiota, as well as STD pathogens, and viruses. Thus, the application of real-time PCR tests can be effectively used in vaginal microbiota evaluation in women with BV, intermediate vaginal microbiota, and healthy women. In addition, this test may be used as an alternative to the Amsel criteria and Nugent scoring method in diagnosing BV.

Microbial composition across body sites in polycystic ovary syndrome: a systematic review and meta-analysis

Polycystic ovary syndrome (PCOS) is an endocrine disorder affecting reproductive-aged women, but the cause remains unclear. Recent evidence has linked microbial composition with PCOS; however, the results are inconsistent. The aim of this systematic review was to gather current knowledge of the microbes across body sites (oral cavity, blood, vagina/cervix, gut) in women with PCOS, and meta-analyse the microbial diversity in PCOS. For this purpose, a systematic search using PubMed, Web of Science, Cochrane and Scopus was carried out. After selection, 34 studies met the inclusion criteria. Most of the studies associated changes in the microbiome with PCOS, whereas heterogeneity of the studies in terms of ethnicity, body mass index (BMI) and methodology, among other confounders, made it difficult to corroborate this relationship. In fact, 19 out of 34 of the studies were categorised as having high risk of bias when the quality assessment was conducted. Our meta-analysis on the gut microbiome of 14 studies demonstrated that women with PCOS possess significantly lower microbial alpha diversity compared with controls (SMD = -0.204; 95% CI -0.360 to -0.048; P = 0.010; I2 = 5.508, by Shannon Index), which may contribute to the development of PCOS. Nevertheless, future studies should specifically overcome the shortcomings of the current studies by through well planned and conducted studies with larger sample sizes, proper negative and positive controls and adequate case-control matching.

Lactobacilli and Their Probiotic Effects in the Vagina of Reproductive Age Women

In the present narrative review, the probiotic effects of vaginal Lactobacillus spp. are described in detail, covering the importance of the differential production of lactic acid, the lactic acid D/L isoforms, the questionable in vivo effect of hydrogen peroxide, as well as bacteriocins and other core proteins produced by vaginal Lactobacillus spp. Moreover, the microbe–host interaction is explained with emphasis on the vaginal mucosa. To understand the crucial role of Lactobacillus spp. dominance in the vaginal microbiota, different dysbiotic states of the vagina are explained including bacterial vaginosis and aerobic vaginitis. Finally, this review takes on the therapeutic aspect of live lactobacilli in the context of bacterial vaginosis. Until recently, there was very low-quality evidence to suggest that any probiotic might aid in reducing vaginal infections or dysbiosis. Therefore, clinical usage or over the counter usage of probiotics was not recommended. However, recent progress has been made, moving from probiotics that are typically regulated as food supplements to so-called live biotherapeutic products that are regulated as medical drugs. Thus, recently, a phase 2b trial using a Lactobacillus crispatus strain as a therapeutic add-on to standard metronidazole showed significant reduction in the recurrence of bacterial vaginosis by 12 weeks compared to placebo. This may constitute evidence for a brighter future where the therapeutic use of lactobacilli can be harnessed to improve women’s health.

Microbiological Assessment of Glycyrrhizic Acid Effectiveness in Bacterial Vaginosis – A Comparative Study

Background. Bacterial vaginosis (BV) is one of the most common female diseases, which is currently characterized by an increasing rate of clinical sign reccurence, the appearance of asymptomatic carriers, and atypical forms. This study was aimed to evaluate the effectiveness of glycyrrhizic acid administration in the prevention of BV recurrence. Materials and Methods. The study involved 88 women after BV treatment (metronidazole per os for seven days). Participants were randomly divided into two groups: the main group included 46 patients who were administered 0.1% glycyrrhizic acid intravaginally for three months after the main treatment; the control group comprised 42 women who received no anti-recurrence BV course. The effectiveness was assessed three and six months after the beginning of treatment and included gynecological examination and laboratory assessments (pH, amine test, microbiological investigation). Results. After recommended BV treatment without anti-recurrence course, the recurrence of laboratory criteria for BV increased three months after the treatment, including the increase in vaginal pH to > 4.5 in all subjects, positive amine test in 35.7% of patients, the presence of Gardnerella vaginalis at a concentration of 104-105 CFU/ml in 31.0% of women, reduction in the frequency of Lactobacillus detection with worsening of the condition and the onset of clinical manifestations of the disease six months later. In the main group, after glycyrrhizic acid administration, laboratory criteria of BV recovery three months after the treatment, and clinical and laboratory markers of BV recovery six months after the treatment were lower as compared to the control group. Conclusions. The anti-recurrence course of BV (vaginal administration of 0.1% glycyrrhizic acid) demonstrated a decrease in the frequency of complaints, clinical and laboratory markers, stabilization of the species composition of Lactobacillus, and a decrease in facultative anaerobe concentration in the vaginal microbiome as compared to group without anti-recurrence treatment.

Endometrial Dysbiosis Is Related to Inflammatory Factors in Women with Repeated Implantation Failure: A Pilot Study

An abnormal endometrial microbiota has been suggested to impair the process of embryo implantation, thus leading to repeated implantation failure (RIF) in women undergoing in vitro fertilization (IVF). However, the molecular mechanisms linking uterine microbiota and IVF out-comes are still an open question. The aim of this cohort study was to outline the relationship between endometrial microbiota, inflammation and IVF outcomes. To this purpose, endometrial microbiota and selected components of the “cytokine network” were analyzed in women presenting RIF and divided between eubiosis and dysbiosis groups, according to the percentage of endometrial lactobacilli (≥90% or <90%, respectively). The Dysbiosis group presented significantly higher tissue concentrations of the inflammatory markers (IL-6, IL-1β, HIF-1α and COX-2) and significantly lower levels of the anti-inflammatory/well-being factors, IL-10 and IGF-1, with respect to women with eubiosis. Moreover, the Lactobacillus percentage was negatively related to the concentrations of the inflammatory molecules and positively related to IL-10/IGF-1. Interestingly, the number of IVF attempts was directly related to the levels of the inflammatory factors COX-2, IL-1β and HIF-1α in the eubiosis group. Overall, endometrial dysbiosis was demonstrated to be associated with inflammation-related endometrial changes affecting the process of embryo implantation, underlining the importance of assessing uterine microbiota in patients undergoing IVF.

Identification of vaginal microbiome associated with IVF pregnancy

The factors that cause a preterm birth (PTB) are not completely understood up to date. Moreover, PTB is more common in pregnancies achieved by in-vitro fertilization (IVF) than in spontaneous pregnancies. Our aim was to compare the composition of vaginal microbiome at 12 weeks of gestation between women who conceived naturally or through IVF in order to study whether IVF PTB-risk could be related to vaginal microbiome composition. We performed an observational, prospective and multicentre study among two public hospitals and a fertility private clinic in Spain. Vaginal swabs from 64 pregnant women at 12 weeks of gestation were collected to analyse the microbiome composition by sequencing the V3-V4 region of the 16S rRNA. Our results showed that the vaginal microbiome signature at 12 weeks of pregnancy was different from women who conceived naturally or through IVF. The beta diversity and the genus composition were different between both cohorts. Gardnerella, Neisseria, Prevotella, and Staphylococcus genus were enriched genus in the vaginal microbiome from the IVF group, allowing us to create a balance model to predict both cohorts. Moreover, at species level the L. iners abundance was higher and L. gasseri was lower in the IVF group. As a conclusion, our findings were consistent with a proposed framework in which IVF pregnancy are related to risk for preterm birth (PTB) suggesting vaginal microbiome could be the reason to the relation between IVF pregnancy and risk for PTB.

Vaginal Dysbiotic Microbiome in Women With No Symptoms of Genital Infections

The vaginal microbiome plays a critical role in determining the progression of female genital tract infections; however, little is known about the vaginal microbiota of Indian women. We aimed to investigate the vaginal microbial architecture of women with asymptomatic bacterial vaginosis (BV) (n=20) and normal microbiota (n=19). Microbial diversity was analyzed in vaginal swabs from regularly menstruating women (18-45yrs) by 16S rRNA V3-V4 amplicon (MiSeq Illumina) sequencing. Rarefaction analysis showed a higher number of species in normal flora compared to BV. Alpha diversity as measured by Pielou’s evenness revealed microbial diversity was significantly greater in BV samples than normal microbiota (p= 0.0165). Beta diversity comparison using UniFrac metrics indicated distinct microbial communities clustering between normal and BV flora. Firmicutes were the major phyla observed in vaginal specimens of normal microbiota whereas Actinobacteria, Fusobacteria, Bacteroidetes were significantly abundant in BV samples. Notably, the relative abundance of Lactobacillus was significantly high in normal microbiota. Conversely Gardnerella, Sneathia, Prevotella, Atopobium, Ureaplasma, Dialister significantly dominated dysbiotic microbiota. Relative frequency of Lactobacillus decreased significantly in BV (6%) as compared to normal microbiota (35.2%). L. fermentum, L. gasseri, L. iners, L. jensenii, L. mucosae, L. ruminis, L. salivarius, L. coleohominis was more exclusively present in normal microbiota. L. iners was detected from both the groups with a relative frequency of 50.4% and 17.2% in normal and BV microbiota respectively. Lefse analysis indicated Atopobium vaginae, Sneathia amnii, Mycoplasma hominis Prevotella disiens in the vaginal microbiota as a biomarker for dysbiosis and L. jensenii as a biomarker of a healthy microbiota. Firmicutes were negatively correlated to Tenericutes, Actinobacteria, Bacteroidetes, and Fusobacteria. Proteobacteria positively correlated to Tenericutes, and Bacteroidetes were shown to be positively correlated to Fusobacteria. Predicted functional analysis indicated differences in the functional profiles between BV and normal microbiota. Normal microbiota utilized pathways essential for phosphatidylglycerol biosynthesis I & II, peptidoglycan biosynthesis, geranylgeranyl diphosphate biosynthesis I, mevalonate pathway, CoA biosynthesis pathway I and pyrimidine nucleotide salvage; whereas BV bacteria had characteristic aromatic amino acid biosynthesis, pentose phosphate pathway, carbohydrate degradation. In conclusion, women with asymptomatic BV have vaginal microbiota significantly different than women with normal microbiota. Furthermore, the study provides insights into the vaginal microbial structure of Indian women that will enable us to explore the prospective candidates for restoring the vaginal microbiota.

Wet Mount Microscopy of the Vaginal Milieu Does Not Predict the Outcome of Fertility Treatments: A Cross-sectional Study

OBJECTIVE

The aim of the study was to evaluate whether vaginal dysbiosis (bacterial vaginosis [BV] or moderate/severe aerobic vaginitis [AV]/desquamative inflammatory vaginitis) in women subjected to intrauterine insemination (IUI) or in vitro fertilization/intracytoplasmic sperm injection influences the rates of pregnancy.

MATERIALS AND METHODS

This is a cross-sectional study involving 392 women who underwent IUI or in vitro fertilization/intracytoplasmic sperm injection at a fertility clinic. All had a slide collected for phase contrast wet mount microscopy (WMM), which was classified according to the International Society for the Study of Vulvovaginal Disease recommendations. Correlation between flora patterns and the rate of pregnancy were evaluated.

RESULTS

There were no differences in any of the groups in terms of pregnancy rate (biochemical, clinical, at first trimester ultrasound, or live birth) after stratifying for the presence of BV, moderate or severe (ms) AV, BV and/or moderate or severe AV, cytolysis, or abnormal vaginal flora (lactobacillary grade ≥ IIb). The presence of Candida species, cocci, or bacilli morphotypes other than lactobacilli also showed no differences.

CONCLUSIONS

The vaginal flora assessment by WMM at the time of IUI or oocyte retrieval was not predictive of the success of fertility treatments.The absence of differences may be due to intrinsic limitations of WMM (i.e., identifying only bacterial morphotypes), a positive impact of the treatments in the vaginal flora or because the sperm and embryo transfer is made directly into the uterine cavity, thus overcoming any cervical or vaginal dysbiosis disadvantage. Future studies should focus on the endometrial milieu, rather than in the vaginal and/or cervical one.

The impact of the female genital tract microbiome in women health and reproduction: a review

PURPOSE

The aim of this review is to gather the available research focusing on female genital tract (FGT) microbiome. Research question focuses in decipher which is the role of FGT microbiota in eubiosis, assisted reproduction techniques (ARTs), and gynaecological disorders, and how microbiome could be utilised to improve reproduction outcomes and to treat fertility issues.

METHODS

PubMed was searched for articles in English from January 2004 to April 2021 for "genital tract microbiota and reproduction", "endometrial microbiome", "microbiome and reproduction" and "microbiota and infertility". Manual search of the references within the resulting articles was performed.

RESULTS

Current knowledge confirms predominance of Lactobacillus species, both in vagina and endometrium, whereas higher variability of species is both found in fallopian tubes and ovaries. Microbial signature linked to different disorders such endometriosis, bacterial vaginosis, and gynaecological cancers are described. Broadly, low variability of species and Lactobacillus abundance within the FGT is associated with better reproductive and ART outcomes.

CONCLUSION

Further research regarding FGT microbiome configuration needs to be done in order to establish a more precise link between microbiota and eubiosis or dysbiosis. Detection of bacterial species related with poor reproductive outcomes, infertility or gynaecological diseases could shape new tools for their diagnosis and treatment, as well as resources to assess the pregnancy prognosis based on endometrial microbiota. Data available suggest future research protocols should be standardised, and it needs to include the interplay among microbiome, virome and mycobiome, and the effect of antibiotics or probiotics on the microbiome shifts.

Identification of Uterine Microbiota in Infertile Women Receiving in vitro Fertilization With and Without Chronic Endometritis

In vitro fertilization (IVF) is an important assisted reproductive technology in treating infertility, whose failure rate is still high. Studies suggested that uterine microbiota are related to women’s reproductive diseases and persisting intrauterine bacterial infectious conditions, such as chronic endometritis (CE), impairing the pregnant processes. However, the relationship between uterine microbiota and IVF outcomes is still an open question. In the present study, 94 patients diagnosed with infertility were enrolled and were divided into CE (E group, n = 25) and non-CE (NE group, n = 69) groups depending on the hysteroscopy and immunohistochemistry. Subsequently, E (Ep, n = 8 and Enp, n = 17) and NE (NEp, n = 41 and NEnp, n = 28) groups were divided into pregnancy and non-pregnancy groups depending on the IVF outcomes, respectively. The uterine fluids were collected and microbial profiles were examined through the V4 region of 16S rRNA gene high-throughput sequencing. The results demonstrated that patients with CE had significantly lower clinical pregnancy rate compared with the non-CE patients (32 vs. 58.42%, p = 0.0014). The relative abundances of Proteobacteria and Acidobacteria were higher in the non-CE group, whereas high abundances of Actinobacteria and Fusobacteria were observed in the CE group at the phylum level. At the genus level, high relative abundances of Gardnerella were observed in the CE group and non-pregnancy groups, which significantly referred to the negative IVF outcome. In conclusion, CE may be a key factor for the negative outcome after IVF, of which the uterine microbiota plays a pivotal role, and the microbial diversity in uterine may serve as a biomarker to forecast the success of IVF outcome.

Bacterial vaginosis: drivers of recurrence and challenges and opportunities in partner treatment

Bacterial vaginosis (BV) is the most common vaginal dysbiosis to affect women globally, yet an unacceptably high proportion of women experience BV recurrence within 6 months of recommended antibiotic therapy. The low rate of sustained cure highlights our limited understanding of the pathogenesis of BV recurrence, which has been attributed to possible persistence and re-emergence of BV-associated bacteria (BVAB) or a BV-associated biofilm following antimicrobials and/or reinfection occurring from sexual partners.There is a robust body of evidence to support the exchange of bacteria between partners during sexual activity, and while the hypothesis that women treated for BV are subsequently reinfected with BVAB following sex with an untreated sexual partner is not new, failure of past partner treatment trials has eroded confidence in this concept. If reinfection is a key driver of recurrence, current antimicrobial regimens directed to women alone are unlikely to achieve a high level of sustained cure, and the approach of partner treatment to reduce reinfection is justified. In this manuscript, we present the molecular and epidemiological evidence that underlies the hypothesis that BV is sexually transmitted, and summarise why research that continues to consider sexual partnerships is necessary. We also outline the significant barriers and challenges that we have identified while undertaking partner treatment studies, and we discuss the factors that impact on our ability to determine their effectiveness.Ultimately, the pathogenesis of BV recurrence is likely to be multifaceted and not attributable to a single mechanism in all women. If we are to achieve sustained cure for women, it is likely that combined and individualised approaches to eradicate BVAB, support an optimal vaginal microbiome, and prevent reinfection from partners will be required.