Microbial flora of the cervix assessed at the time of embryo transfer adversely affects in vitro fertilization outcome

Clinical Applicability of Microbiota Sampling in a Subfertile Population: Urine versus Vagina

The urogenital microbiota is increasingly gaining recognition as a significant contributor to reproductive health. Recent studies suggest that microbiota can serve as predictors for fertility treatment outcomes. Our objective was to investigate the degree of similarity in microbial composition between patient-collected urine and vaginal samples in a subfertile population. We enrolled women of reproductive age (20-44 years) diagnosed with subfertility and requiring in vitro fertilization (IVF) or IVF with intracytoplasmic sperm injection (IVF-ICSI) treatment. They self-collected both mid-stream urine samples and vaginal swabs before commencing the IVF or IVF-ICSI procedure. All samples were analysed using the intergenic spacer profiling (IS-pro) technique, a rapid clinical microbiota analysis tool. The main outcome measures were the degree of similarity of microbial composition between the two different, but simultaneously collected, samples. Our findings revealed a high correlation (R squared of 0.78) in microbiota profiles between paired urine and vaginal samples from individual patients. Nevertheless, the urinary microbiota profiles contained fewer species compared to the vaginal microbiota, resulting in minor but distinguishable differences. Furthermore, different subfertility diagnoses appeared to be associated with differences in microbial profiles. A noteworthy observation was the exclusive presence of Escherichia coli (E. coli) in both samples of women diagnosed with male factor subfertility. In conclusion, since urinary microbiota profiles seem to represent a diluted version of the vaginal microbiota, vaginal microbiome sampling to predict fertility treatment outcome seems preferable. To enhance the success of fertility treatments, further research is needed to gain deeper insights into a putative causal role of microbiota in the mechanisms of subfertility.

Interaction of semen with female reproductive tract tissues: what we know, what we guess and what we need to do

For nearly 100 years the postcoital inflammatory response has been described in the female reproductive tract of rodents. Since the 1950's this observation has been made in a number of animals including humans and domestic species. Yet pregnancy can be initiated and maintained by using embryo transfer which bypasses insemination and the related postcoital inflammatory response. Thus, the role of semen exposure beyond sperm transport and subsequent postcoital inflammatory response in female reproductive tissues has yet to be given a true physiological purpose. Historically the postcoital inflammatory response of female tissues was suggested to remove spermatozoa and male derived pathogens from the female reproductive tract. More recently, semen exposure and the postcoital inflammatory response have been suggested to play a role in long-term preparation of the maternal immune system to the semi-allogeneic pregnancy, ancillary support of the preimplantation embryo, and potentially fetal programing that improves pregnancy outcomes, while the absence or inappropriate postcoital inflammation has been suggested to contribute to pregnancy complications. Although the postcoital inflammatory response has been robustly characterized, the evidence for its role in promoting positive pregnancy outcomes or reducing pregnancy complications remains tenuous. This manuscript is designed to balance the information we know regarding semen exposure and postcoital inflammation in various animal systems, with the information we perceive to be factual but perhaps not yet fully tested, along with the data we have yet to generate if we intend to postulate a physiological purpose of the postcoital inflammatory response to pregnancy outcomes.

Microbiome in Female Reproductive Health: Implications for Fertility and Assisted Reproductive Technologies

The microbiome plays a critical role in the process of conception and the outcomes of pregnancy. Disruptions in microbiome homeostasis in women of reproductive age can lead to various pregnancy complications, which significantly impact maternal and fetal health. Recent studies have associated the microbiome in the female reproductive tract (FRT) with assisted reproductive technology (ART) outcomes, and restoring microbiome balance has been shown to improve fertility in infertile couples. This review provides an overview of the role of the microbiome in female reproductive health, including its implications for pregnancy outcomes and ARTs. Additionally, recent advances in the use of microbial biomarkers as indicators of pregnancy disorders are summarized. A comprehensive understanding of the characteristics of the microbiome before and during pregnancy and its impact on reproductive health will greatly promote maternal and fetal health. Such knowledge can also contribute to the development of ARTs and microbiome-based interventions.

Comparison of microbial abundance and diversity in uterine and peritoneal fluid in infertile patients with or without endometriosis

INTRODUCTION

Endometriosis (EM) is a multifactorial disease that affects 10 - 15% of women of reproductive age. Additionally, 30-50% of women with EM suffer from infertility. The mechanism of infertility caused by EM has not yet been consistently explained. In recent years, studies have shown a link between infertility associated with EM and changes in the reproductive tract microbiota.

METHODS

In this study, we involved 26 EM patients (8 cases of stage I-II and 18 cases of stage III-IV) and 31 control subjects who were tubal obstruction-related infertility (TORI). The samples from peritoneal fluid (PF) and uterine fluid (UF) were collected and sequenced by 16 S rRNA amplicon.

RESULTS

In the comparison of microbial diversity, we found no significant differences in the microbial diversity of PF and UF between patients with stage I-II EM and those with TORI. However, there was a significant difference in microbial diversity among patients with stage III-IV EM compared to the previous two groups. Lactobacillus decreased in PF of EM compared to the control group, while it increased in UF. In PF, the abundance of Pseudomonas, Enterococcus, Dubosiella and Klebsiella was significantly higher in patients with stage III-IV compared to TORI patients. And in UF, the main differences existed between stage I-II EM compared to the other two groups. The abundance of pontibacter, aquabacterium, Rikenellaceae and so on at the genus level was significantly enriched in the EM patients with stage I-II. In the analysis based on KEGG database, EM may affect the receptivity related pathways of the endometrium by influencing changes in the uterine microbiota.

CONCLUSION

Our results indicated that as EM progresses, the microorganisms in UF and PF keep changing. These changes in the microbiota, as well as the resulting alternations in gene functional classification, may play an important role in the infertility associated with EM.

Longitudinal analysis of vaginal microbiota during IVF fresh embryo transfer and in early pregnancy

IMPORTANCE

Infertility is a global public health issue which leads many couples to seek fertility treatments, of which in vitro fertilization (IVF) is considered to be the most effective. Still, only about one-third of the women achieve live birth after the first IVF embryo transfer (IVF-ET). Factors affecting embryo implantation are poorly known, but the female reproductive tract microbiota may play a key role. Our study confirms the beneficial role of vaginal lactobacilli, especially Lactobacillus crispatus, in the probability of achieving clinical pregnancy and live birth following IVF-ET. Our findings regarding the intra-individual shift of vaginal microbiota between non-pregnancy and pregnancy states are novel and provide new information about the dynamics of microbiota in the early steps of human reproduction. These findings may help clinicians in their attempts to optimize the conditions for ET by microbiota screening or modulation and timing the ET when the microbiota is the most favorable.

Antibiotics prior to or at the time of embryo transfer in ART

BACKGROUND

After an assisted reproductive technology (ART) cycle, embryo transfer (ET) involves the placement of one or more embryos into the uterine cavity, usually by passing a catheter through the cervical os. Despite the transfer of high-quality embryos, many ETs do not result in a pregnancy. There are many factors that may affect the success of ET. There is some evidence to suggest that increased endocervical microbial colonization at the time of ET results in lower pregnancy rates. The association between the cervico-vaginal microbiome and reduced pregnancy rates after ET may indicate either pre-existing dysbiosis in this patient population, or that the passage of the ET catheter itself may be introducing microbes that alter the microbiome of the endometrial cavity or lead to infection. Such an upper genital tract infection, contamination or alteration may have a negative impact on implantation and in vitro fertilization (IVF) success rates by both endometrial and embryonic mechanisms. The administration of antibiotics at the time of ET has been suggested as an intervention to reduce levels of microbial colonization and hence improve pregnancy rates.

OBJECTIVES

To evaluate the benefits and harms of antibiotic administration prior to or at the time of embryo transfer (ET) during assisted reproductive technology (ART) cycles.

SEARCH METHODS

We searched the Cochrane Gynaecology and Fertility (CGF) Group trials register, CENTRAL (now containing output from two trial registers and CINAHL), MEDLINE, Embase and PsycINFO, together with reference checking and contact with study authors and experts in the field to identify additional studies. The search date was November 2022.

SELECTION CRITERIA

We included two randomized controlled trials (RCT) that compared antibiotics administered by any route versus no antibiotics prior to ET.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures recommended by Cochrane, including assessing risk of bias of the included studies using the RoB 2 tool. The primary review outcome was live birth rate (LBR) or ongoing pregnancy, and secondary outcomes were clinical pregnancy rate (CPR), genital tract colonization rate, miscarriage rate, ectopic pregnancy rate, multiple pregnancy rate, fetal abnormalities, adverse events and pelvic infection.

MAIN RESULTS

We included two RCTs with 377 women in the review. Using the GRADE method, we assessed the certainty of the evidence as very low to low across measured outcomes. We are uncertain whether antibiotics given prior to or at the time of ET improved LBR (odds ratio (OR) 0.48, 95% confidence interval (CI) 0.10 to 2.23; 1 study, 27 women; low-certainty evidence). The evidence suggests that if LBR without antibiotics was 60%, the rate with antibiotics would be between 13% and 77%. We are uncertain whether antibiotics given prior to or at the time of ET improve CPR (OR 1.01, 95% CI 0.67 to 1.55; I² = 0%; 2 studies, 377 women; low-certainty evidence). If the CPR without antibiotics was 37%, the rate with antibiotics would be between 29% and 48%. The administration of antibiotics prior to or at the time of ET may reduce genital tract colonization slightly (OR 0.59, 95% CI 0.37 to 0.95; 1 study, 130 women; very low-certainty evidence). If the genital tract colonization rate without antibiotics was 29%, the rate with antibiotics would be between 13% and 28%. However, this did not correspond to an effect on the pregnancy outcome. Only one study with low numbers of women reported on miscarriage rate, with one miscarriage reported in the group not receiving antibiotics (OR 4.04, 0.15 to 108.57; 1 study, 27 women; low-certainty evidence). There was insufficient evidence to reach a conclusion regarding adverse effects and other outcomes as no studies reported data suitable for analysis.

AUTHORS' CONCLUSIONS

We are uncertain if administration of antibiotics prior to or at the time of ET improves LBR in women undergoing ART based on a single study of 27 women with low-certainty evidence. We are uncertain whether there was a difference in CPR. There was evidence for a reduction in genital tract colonization rates, but the evidence was very low certainty. Data were lacking on other secondary outcomes. The pooled results should be interpreted with caution, due to the small number of women included in the analysis.

Impact of sexual intercourse on frozen-thawed embryo transfer outcomes: a randomized controlled trial

BACKGROUND

Exposure of the female reproductive tract to either seminal plasma or fluid component of the ejaculate is beneficial to achieving successful embryo implantation and normal embryo development. But whether the "physical" component of sexual intercourse during the peri-transfer period have any influence on frozen-thawed embryo transfer (FET) pregnancy outcomes is not clear.

METHODS

We conducted a randomized trial that included 223 patients undergoing in vitro fertilization (IVF) treatment at a university-affiliated reproductive center from 19 July 2018 to 24 February 2019. Enrolled patients undergoing IVF treatment were randomized either to engage sexual intercourse using the barrier contraception (Group A, n = 116) or to abstain (Group B, n = 107) one night before FET. The primary outcome was clinical pregnancy rate.

RESULTS

Patients having intercourse had higher clinical pregnancy rate (51.72% vs. 37.07%, P = 0.045) and implantation rate (38.31% vs. 24.77%, P = 0.005) compared to those did not engage intercourse. However, there was no significant difference of the spontaneous abortion rate between two groups (11.67% 33 vs. 14.63%, P = 0.662).

CONCLUSIONS

Sexual intercourse before embryo transfer may improve the clinical pregnancy and implantation rates during FET cycles. However, it should be noted that patients choose only one time for sexual intercourse, that is, the night before embryo transfer.

TRIAL REGISTRATION

The present study was registered at the Chinese Clinical Trial Registry ( http://www.chictr.org.cn/ , ChiCTR1800017209).

Endometrial receptivity array before frozen embryo transfer cycles: a systematic review and meta-analysis

OBJECTIVE

To investigate the impact of endometrial receptivity array (ERA) before frozen embryo transfer in patients undergoing in vitro fertilization (IVF). There is a lack of consensus regarding the use of ERA for increasing the success rate of IVF cycles, mainly in terms of the live birth rate.

DESIGN

PubMed, Web of Science and Embase were searched from inception up to February 15, 2022.

SETTING

Not applicable.

PATIENT(S)

Patients undergoing ERA vs no ERA before frozen embryo transfer.

INTERVENTION(S)

Only comparative studies evaluating pregnancy rates of patients undergoing frozen embryo transfer cycles with or without prior ERA were included. Inter-study heterogeneity was also assessed using Cochrane's Q test and the I² statistic. The random-effects model was used to pool the odds ratio (OR) with the corresponding 95% confidence intervals (CIs). Subgroup analyses were performed to investigate the impact of ERA on pregnancy rates according to the number of previous embryo transfer (ET) failures (≤ 2 previous failed ETs vs. > 2 failed ETs, defined as recurrent implantation failure). Separate analyses were performed according to the study design and adjustment for confounders.

MAIN OUTCOME MEASURES(S)

The primary outcomes of the study were live birth rate and/or ongoing pregnancy rate. Implantation rate, biochemical pregnancy rate, clinical pregnancy rate, and miscarriage rate were considered secondary outcomes.

RESULT(S)

Eight studies (representing data on n = 2,784 patients; n = 831 had undergone ERA and n = 1,953 without ERA) were found to be eligible for this meta-analysis. The live birth or ongoing pregnancy rate for the ERA group was not significantly different compared with the non-ERA group (OR, 1.38; 95% CI, 0.79-2.41; I² 83.0%), nor was a difference seen in subgroup analyses based on the number of previous failed ETs. The rates of implantation, biochemical pregnancy, clinical pregnancy, and miscarriage were also comparable between the ERA and the non-ERA groups. After separate analyses according to the study design and adjustment for confounding factors, overall pooled estimates remained statistically nonsignificant.

CONCLUSION(S)

The findings of the current meta-analysis did not reveal a significant change in the rate of pregnancy after IVF cycles using ERA, and it is not clear whether ERA can increase the pregnancy rate or not.

SYSTEMATIC REVIEW REGISTRATION

Prospectively registered in PROSPERO (CRD42022310862).

Adverse effect of lactobacilli-depauperate cervicovaginal microbiota on pregnancy outcomes in women undergoing frozen-thawed embryo transfer

Purpose

The cervicovaginal microbiota is essential for maintaining the health of the female reproductive tract. However, whether cervicovaginal microbiota status prior to frozen embryo transfer (FET) associates with pregnancy outcomes is largely unexplored.

Methods

Cervical mucus from 29 women who had undergone FET was collected. Microbial composition was analyzed using 16 S rRNA gene sequence to assess the correlation to the pregnancy outcomes.

Results

CST-categorized Lactobacillus was the most dominant (41.71%) in the pregnant group, while CST-IV-based and BV-related Gardnerella (34.96%) prevailed in the non-pregnant group. The average abundance of Gardnerella compared non-pregnant to pregnant women was the highest (34.96% vs. 4.22%, p = 0.0015) among other CST-IV indicator bacteria. Multivariate analysis revealed that CST-IV-related bacteria have a significantly adverse effect on ongoing pregnancy outcomes (odds ratio, 0.083; 95% confidence index, 0.012-0.589, p = 0.013*).

Conclusions

The study found that the CST-IV microbiota, with significantly increasing Gardnerella and the loss of Lactobacilli as the dominant bacteria, can potentially contribute to pregnancy failure. Therefore, dysbiotic microbiota may be a risk factor in women undergoing FET. Assessing the health of the cervicovaginal microbiota prior to FET would enable couples to make a more thoughtful decision on the timing and might improve pregnancy outcomes.

Therapeutic intervention based on gene sequencing analysis of microbial 16S ribosomal RNA of the intrauterine microbiome improves pregnancy outcomes in IVF patients: a prospective cohort study

PURPOSE

A Lactobacillus-dominated microbiota in the endometrium was reported to be associated with favorable reproductive outcomes. We investigated in this study whether 16S ribosomal RNA (rRNA) gene sequencing analysis of the uterine microbiome improves pregnancy outcomes.

METHODS

This prospective cohort study recruited a total of 195 women with recurrent implantation failure (RIF) between March 2019 and April 2021 in our fertility center. Analysis of the endometrial microbiota by 16S rRNA gene sequencing was suggested for all patients who had three or more failed embryo transfers (ETs). One hundred and thirty-one patients underwent microbial 16S rRNA gene sequencing (study group) before additional transfers, while 64 patients proceeded to ET without that analysis (control group). The primary outcome was to compare the cumulative clinical pregnancy rate of two additional ETs.

MAIN RESULTS

An endometrial microbiota considered abnormal was detected in 30 patients (22.9%). All but one of these 30 patients received antibiotics according to the bacterial genus detected in their sample, followed by treatment with probiotics. As a result, the cumulative clinical pregnancy rate (study group: 64.5% vs. control group: 33.3%, p = 0.005) and the ongoing pregnancy rate (study group: 48.9% vs. control group: 32.8%, p = 0.028) were significantly increased in the study group compared to the control group.

CONCLUSION

Personalized treatment recommendations based on the microbial 16S rRNA gene sequencing of the uterine microbiota can improve IVF outcomes of patients with RIF.

TRIAL REGISTRATION

The University Hospital Medical Information Network (UMIN) Clinical Trial Registry: UMIN000036050 (date of registration: March 1, 2019).

Effect of vaginal flora on clinical outcome of frozen embryo transfer

Objective

Vaginal microbiota imbalance is a high risk factor for premature birth, and is closely related to female pelvic inflammation and sexually transmitted diseases. The effect of vaginal microbiota on the outcome of assisted reproductive technology is still unclear. In this study, the vaginal microbial composition and the pregnancy outcome of frozen embryo transfer (FET) was investigated.

Methods

From October 2020 to December 2021, 275 FET cycles were selected from the center of reproductive medicine in Affiliated Hospital of Nantong University. Vaginal secretions were collected on the day of endometrium transformation, and smears were Gram stained. According to the Nugent score they were divided into three groups, including normal group, mild dysbiosis group and sever dysbiosis group. The clinical outcomes of each group were compared.

Results

In 275 FET cycles, the embryo implantation rate, clinical pregnancy rate and ongoing pregnancy rate in the normal group (66.9%,84.3% and 83.1%) were significantly higher than those in the mild dysbiosis group (45.5%, 57.3% and 49.3%) and in sever dysbiosis group (29.6%, 34.2% and 27%). The difference was statistically significant (P<0.01). When compared the preclinical pregnancy loss rate and the miscarriage rate, the normal group (1.3% and 1.3%) was significantly lower than those in the mild dysbiosis group (20.4% and 14.0%) and the sever dysbiosis group (25.5% and 21.1%). The difference was statistically significant (P<0.01), but there was no significant difference between the mild dysbiosis group and sever dysbiosis group (P>0.05).

Conclusion

Nugent score is directly related to the clinical outcome of FET. The Lactobacilli-dominant vaginal flora was a favorable factor for the good clinical outcome of FET, while asymptomatic bacterial vaginosis had a negative correlation with the outcome of FET.

Genital Microbiota and Outcome of Assisted Reproductive Treatment-A Systematic Review

The balance between different bacterial species is essential for optimal vaginal health. Microbiome includes the host genome along with microorganism genomes and incorporates the biotic and abiotic factors, reflecting the habitat as a whole. A significant difference exists in the composition and number of the human microbiota in healthy individuals. About one-tenth of the total body microbiota exists in the urogenital tract and these can be identified by microscopy and culture-based methods, quantitative PCR, next generation and whole genome sequencing. The trend of delaying the planning of pregnancy to a later age nowadays has resulted in magnifying the use of assisted reproductive treatment (ART). Hence, genital microbiota and its impact on fertility has generated immense interest in recent years. In this systematic review, we searched the available evidence on the microbiota of the genital tract in women undergoing ART and studied the outcomes of IVF in different microbial compositions. Despite the inconsistency of the studies, it is evident that vaginal, cervical and endometrial microbiota might play a role in predicting ART outcomes. However, there is no clear evidence yet on whether the diversity, richness, quantity, or composition of species in the maternal genital tract significantly affects the outcomes in ARTs.

Microbiology of Human Follicular Fluid and the Vagina and Its Impact on in Vitro Fertilization Outcomes

PURPOSE

The present study aimed to identify microorganisms in follicular fluids and to investigate their association with in vitro fertilization (IVF) outcomes.

MATERIALS AND METHODS

This study was conducted as a prospective study of 49 infertile females undergoing IVF/intracytoplasmic sperm injection cycles between 2013 and 2016. Paired follicular fluid and vaginal secretions were collected on the day of ovum pick up and were cultured to detect microorganisms.

RESULTS

Fifteen women (30.6%) had no microorganisms in follicular fluid or vaginal swabs, 23 (46.9%) had microorganisms on vaginal swab alone, 3 (6.1%) had microorganisms in follicular fluid alone, and 8 (16.3%) had microorganisms in both follicular fluid and vaginal swabs. The same microorganisms were detected in both the follicular fluid and vaginal swabs of three women, while different microorganisms were detected between follicular fluid and vaginal swabs in five women. Follicular fluid microorganisms were not associated with embryo quality or clinical pregnancy rates during IVF cycles. However, significantly decreased implantation rates (9.1% vs. 29.4%, p=0.031) and clinical pregnancy rates on embryo transfer day 5 (0% vs. 83.3%, p=0.048) were observed in the group that was positive for vaginal pathogens.

CONCLUSION

Follicular fluid contains microorganisms that can differ from those in the vagina of the same women; however, they do not appear to be associated with embryo quality or clinical pregnancy rates in IVF cycles. In contrast, vaginal pathogens were found to be associated with worse implantation rates and clinical pregnancy rates in IVF cycles.

Endometrial microbiota composition is associated with reproductive outcome in infertile patients

BACKGROUND

Previous evidence indicates associations between the female reproductive tract microbiome composition and reproductive outcome in infertile patients undergoing assisted reproduction. We aimed to determine whether the endometrial microbiota composition is associated with reproductive outcomes of live birth, biochemical pregnancy, clinical miscarriage or no pregnancy.

METHODS

Here, we present a multicentre prospective observational study using 16S rRNA gene sequencing to analyse endometrial fluid and biopsy samples before embryo transfer in a cohort of 342 infertile patients asymptomatic for infection undergoing assisted reproductive treatments.

RESULTS

A dysbiotic endometrial microbiota profile composed of Atopobium, Bifidobacterium, Chryseobacterium, Gardnerella, Haemophilus, Klebsiella, Neisseria, Staphylococcus and Streptococcus was associated with unsuccessful outcomes. In contrast, Lactobacillus was consistently enriched in patients with live birth outcomes.

CONCLUSIONS

Our findings indicate that endometrial microbiota composition before embryo transfer is a useful biomarker to predict reproductive outcome, offering an opportunity to further improve diagnosis and treatment strategies. Video Abstract.

The Role of Genital Tract Microbiome in Fertility: A Systematic Review

The human microbiome plays a crucial role in determining the health status of every human being, and the microbiome of the genital tract can affect the fertility potential before and during assisted reproductive treatments (ARTs). This review aims to identify and appraise studies investigating the correlation of genital microbiome to infertility. Publications up to February 2021 were identified by searching the electronic databases PubMed/MEDLINE, Scopus and Embase and bibliographies. Only full-text original research articles written in English were considered eligible for analysis, whereas reviews, editorials, opinions or letters, case studies, conference papers, and abstracts were excluded. Twenty-six articles were identified. The oldest studies adopted the exclusive culture-based technique, while in recent years PCR and RNA sequencing based on 16S rRNA were the most used technique. Regardless of the anatomical site under investigation, the Lactobacillus-dominated flora seems to play a pivotal role in determining fertility, and in particular Lactobacillus crispatus showed a central role. Nonetheless, the presence of pathogens in the genital tract, such as Chlamydia trachomatis, Gardnerella vaginalis, Ureaplasma species, and Gram-negative stains microorganism, affected fertility also in case of asymptomatic bacterial vaginosis (BV). We failed to identify descriptive or comparative studies regarding tubal microbiome. The microbiome of the genital tract plays a pivotal role in fertility, also in case of ARTs. The standardization of the sampling methods and investigations approaches is warranted to stratify the fertility potential and its subsequent treatment. Prospective tubal microbiome studies are warranted.

Contribution of Lactobacillus iners to Vaginal Health and Diseases: A Systematic Review

Lactobacillus iners, first described in 1999, is a prevalent bacterial species of the vaginal microbiome. As L. iners does not easily grow on de Man-Rogosa-Sharpe agar, but can grow anaerobically on blood agar, it has been initially overlooked by traditional culture methods. It was not until the wide application of molecular biology techniques that the function of L. iners in the vaginal microbiome was carefully explored. L. iners has the smallest genome among known Lactobacilli and it has many probiotic characteristics, but is partly different from other major vaginal Lactobacillus species, such as L. crispatus, in contributing to the maintenance of a healthy vaginal microbiome. It is not only commonly present in the healthy vagina but quite often recovered in high numbers in bacterial vaginosis (BV). Increasing evidence suggests that L. iners is a transitional species that colonizes after the vaginal environment is disturbed and offers overall less protection against vaginal dysbiosis and, subsequently, leads to BV, sexually transmitted infections, and adverse pregnancy outcomes. Accordingly, under certain conditions, L. iners is a genuine vaginal symbiont, but it also seems to be an opportunistic pathogen. Further studies are necessary to identify the exact role of this intriguing species in vaginal health and diseases.

The Microbial Composition of Lower Genital Tract May Affect the Outcome of in vitro Fertilization-Embryo Transfer

Objective: This work was conducted in order to study the effect of the lower genital tract (vaginal and cervical canal) microbiota on pregnancy outcomes of reproductive-aged women receiving embryo transfer.

Study design: A total of 150 reproductive-aged patients who received the first fresh in vitro fertilization-embryo transfer (IVF-ET) were included in the study. Samples from the vagina and cervical site of each patient were collected separately using sterile swabs before ET. Genomic DNA was pyrosequenced for the V3–V4 regions of the 16S ribosomal RNA gene. Further bioinformatics analysis was performed using QIIME and R package. Pregnancy outcomes were followed and analyzed to compare differences in microbial composition.

Results: The cervical microbiota had a higher Shannon index than the vaginal microbiota, and the microbial composition was different between the two sites. However, the Sorenson index between the two sites within the same individual was 0.370 (0.309–0.400). A total of 89 patients achieved clinical pregnancy after ET, while 61 failed. The Shannon indices and the microbial community of both vaginal and cervical microbiota between pregnant and non-pregnant groups were not significantly different. The relative abundance of Lactobacillus in the vagina and cervical canal did not differ between the two groups. Linear discriminant analysis, random forest analysis, and receiver-operating characteristic curve analysis showed that Bifidobacterium, Prevotella, and Lactobacillus iners in the vagina, as well as Solanum torvum, Fusobacterium, and Streptococcus in the cervix, may be negatively associated with clinical pregnancy after IVF.

Conclusion: The cervical microbiota was more diverse than the vaginal microbiota, but because of anatomical continuity, there was a correlation between the two sites. The microbial composition of the vagina and cervical canal may influence the outcome of IVF-ET, but more samples are needed to verify this conclusion.

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

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.

To understand the reproductive tract microbiome associated with infertility through metagenomics analysis

Background

Knowledge of the microbiome is in its infancy in health and human illness, especially concerning human reproduction. We will be better able to treat dysbiosis of the reproductive tract clinically if it is better explained and understood. It has been shown that altered vaginal microbiota affects parturition, and its function is uncertain in assisted reproductive technologies. However, the effects of recognized microbes such as Mycoplasma tuberculosis, Chlamydia trachomatis, and Neisseria gonorrhoeae are well established, resulting in subclinical changes which are considered to be risk factors for infertility and poor reproductive outcomes.

Main body

Recent studies indicate that the vaginal tract comprises several different organisms of the microbiome. Some microbiota can play an important role not only in the reproductive tract but also in overall health. The microbiome of the female reproductive tract has been identified mainly based on studies that examine vaginal samples across many reproductive technologies, using a metagenomics approach.

Conclusion

Alteration of reproductive tract microbiota or presence of certain microbiota irrespective of the level of pathogenicity may interfere with fertilization, implantation, and subsequent embryo development. This may lead to failed fertility treatments and reduced live birth rate (LBR).

The effect of endocervical and catheter bacterial colonisation during in vitro fertilisation and embryo transfer (IVF-ET) on IVF success rate among asymptomatic women: a longitudinal prospective study

The adverse effects of bacterial contamination during in vitro fertilisation and embryo transfer (IVF-ET) have been studied previously. However, data on asymptomatic women with positive bacterial culture and their IVF outcome are lacking. This prospective longitudinal study was conducted on 74 women undergoing IVF-ET, of whom specimens from the endocervix and ET catheter were taken and sent to a laboratory for microbiological assessment. Then, patients were followed up for evaluation of chemical pregnancy (β-HCG > 25 mIU/mL) and clinical pregnancy (detected foetal heartbeat). The findings revealed that there was no significant difference in terms of biochemical (35.4% vs. 19.2%, p= .116) and clinical pregnancy rate (25.0% vs. 15.4%, p= .257) among ET catheter culture positive and negative women. This finding allows us to conclude that the positive culture in the absence of clinical signs of infection may not increase the risk of implantation failure.Impact StatementWhat is already known on this subject? There is growing evidence indicating that endometritis may decrease the endometrial receptiveness in in vitro fertilisation (IVF) cycles; however, there is a paucity of knowledge regarding IVF outcomes when the bacterial culture of embryo transfer (ET) catheter is positive.What the results of this study add? The present study demonstrates that positive ET catheter culture in asymptomatic women does not increase the risk of IVF failure.What the implications are of these findings for clinical practice and/or further research? Positive-culture, per se, may not be associated with poor IVF outcomes and further studies should be undertaken on this topic in various clinical settings using different protocols.

The vaginal microbiota composition of women undergoing assisted reproduction: a prospective cohort study

OBJECTIVE

To evaluate the impact of vaginal microbiota on pregnancy outcomes in women undergoing assisted reproduction.

DESIGN

A prospective cohort study.

SETTING

A university-based assisted reproductive technology (ART) centre.

POPULATION

223 women undergoing ART treatment.

METHODS

Prior to embryo transfer, vaginal samples were collected from the posterior fornix. Vaginal microbiota identification was carried out using next-generation sequencing and categorised according to the V3-V4 hypervariable region in the 16S rRNA gene region.

MAIN OUTCOME MEASURES

ART clinical outcomes (implantation, clinical pregnancy rates and live birth rates).

RESULTS

The live birth rate in women with community state type (CST)-I (39%) was higher than that in women with CST-III (21.5%) but the difference was not statistically significant (P = 0.052). The relative abundance of Lactobacillus was lower in women who failed to become pregnant (NP group) (67.71%) than in women who became pregnant (PR group) (79.72%). However, this difference was not statistically significant (P = 0.06). In the NP group, the relative abundance of Streptococcus (7.81%) and Gardnerella (9.40%) was higher than that in the PR group (relative abundance of Streptococcus and Gardnerella was 2.28% and 5.56%, respectively). The abundance of Streptococcus was found to be statistically significantly different between the two study groups (P = 0.014). Linear discriminant analysis (LDA) further validated that Streptococcus had the highest contribution (LDA score >4.0) to the difference between these two groups.

CONCLUSIONS

Streptococcus has the highest contribution to the distinction between the PR and NP groups.

TWEETABLE ABSTRACT

A relatively high abundance of Streptococcus in the vaginal microbiota may be associated with a lower ART success rate.

When a Neonate Is Born, So Is a Microbiota

In recent years, the role of human microbiota as a short- and long-term health promoter and modulator has been affirmed and progressively strengthened. In the course of one’s life, each subject is colonized by a great number of bacteria, which constitute its specific and individual microbiota. Human bacterial colonization starts during fetal life, in opposition to the previous paradigm of the “sterile womb”. Placenta, amniotic fluid, cord blood and fetal tissues each have their own specific microbiota, influenced by maternal health and habits and having a decisive influence on pregnancy outcome and offspring outcome. The maternal microbiota, especially that colonizing the genital system, starts to influence the outcome of pregnancy already before conception, modulating fertility and the success rate of fertilization, even in the case of assisted reproduction techniques. During the perinatal period, neonatal microbiota seems influenced by delivery mode, drug administration and many other conditions. Special attention must be reserved for early neonatal nutrition, because breastfeeding allows the transmission of a specific and unique lactobiome able to modulate and positively affect the neonatal gut microbiota. Our narrative review aims to investigate the currently identified pre- and peri-natal factors influencing neonatal microbiota, before conception, during pregnancy, pre- and post-delivery, since the early microbiota influences the whole life of each subject.

Association of vaginal bacterial communities and reproductive outcomes with prophylactic antibiotic exposure in a subfertile population undergoing in vitro fertilization: a prospective exploratory study

OBJECTIVE

To determine whether prophylactic azithromycin is associated with the vaginal bacterial microbiome and clinical outcomes in subfertile women undergoing in vitro fertilization (IVF).

DESIGN

Prospective exploratory cohort study.

SETTING

Single academic fertility center.

PATIENTS

Subfertile women aged 18-43 years undergoing their first IVF cycle and fresh embryo transfer.

INTERVENTION

Primary exposure to prophylactic azithromycin (1 g orally) once at baseline.

MAIN OUTCOME MEASURES

The primary outcome was the effect of azithromycin on the vaginal microbiome compared with a no-azithromycin group at 3 time points throughout the IVF cycle (baseline, retrieval, and embryo transfer). The secondary outcomes were associations of vaginal bacterial communities with clinical outcomes.

RESULTS

A planned a priori exploratory cohort of 27 subjects (12 in the azithromycin treatment group and 15 in the no-azithromycin group) contributed 79 vaginal swabs for the analysis as part of an ongoing randomized, controlled noninferiority trial. No specific taxa were associated with azithromycin or pregnancy at any time point. Azithromycin did not affect alpha diversity or community stability. Although there were trends of a lower bacterial load and higher percentage of Lactobacillus species in the azithromycin group at the time of transfer, these were not statistically significant. In women who did not become pregnant, the percentage of Lactobacillus species was lower (P = .048; Hodges-Lehmann estimate of difference, 0.41; 95% confidence interval, 0.08-0.65) and the change in community composition over time was higher. The percentage of Lactobacillus species at baseline was not predictive of the percentage of Lactobacillus species at the time of embryo transfer.

CONCLUSIONS

Prophylactic azithromycin at baseline is not associated with changes in vaginal bacterial communities. Bacterial community features at the time of embryo transfer are associated with pregnancy. Bacterial community structures at baseline are not predictive of those at the time of embryo transfer.

CLINICAL TRIAL REGISTRATION NUMBER

NCT03386227.

Impact of endometrial microbiome on fertility

Background

Next-generation sequencing isolates culturable and unculturable bacteria from the female reproductive tract. Current literatures surrounding the impact of endometrial microbiome on fertility are reviewed.

Main body

An abnormal endometrial microbiota has been associated with implantation failure pregnancy loss and other gynecological and obstetrical conditions. Identification of endometrial dysbiosis as a new cause of infertility opens a new microbiological field in the evaluation of endometrial factor, highlighting the relevance of assessing the uterine microbiota in infertile patients to restore a favorable endometrial flora in those patients with altered uterine microbiota to improve and personalize the clinical care of infertile patients. Understanding the significance of microbiome in the endometrium may completely change the therapeutic approach in the treatment of this part of the reproductive tract.

Conclusion

Investigation of the endometrial microbiota may be a future tool for improving reproductive outcomes in infertile patients. Further well-designed studies are required to establish its role in the evaluation and treatment of infertile patients

Application of Ligilactobacillus salivarius CECT5713 to Achieve Term Pregnancies in Women with Repetitive Abortion or Infertility of Unknown Origin by Microbiological and Immunological Modulation of the Vaginal Ecosystem

In this study, the cervicovaginal environment of women with reproductive failure (repetitive abortion, infertility of unknown origin) was assessed and compared to that of healthy fertile women. Subsequently, the ability of Ligilactobacillus salivarius CECT5713 to increase pregnancy rates in women with reproductive failure was evaluated. Vaginal pH and Nugent score were higher in women with reproductive failure than in fertile women. The opposite was observed regarding the immune factors TGF-β 1, TFG-β 2, and VEFG. Lactobacilli were detected at a higher frequency and concentration in fertile women than in women with repetitive abortion or infertility. The metataxonomic study revealed that vaginal samples from fertile women were characterized by the high abundance of Lactobacillus sequences, while DNA from this genus was practically absent in one third of samples from women with reproductive failure. Daily oral administration of L. salivarius CECT5713 (~9 log₁₀ CFU/day) to women with reproductive failure for a maximum of 6 months resulted in an overall successful pregnancy rate of 56%. The probiotic intervention modified key microbiological, biochemical, and immunological parameters in women who got pregnant. In conclusion, L. salivarius CECT5713 has proved to be a good candidate to improve reproductive success in women with reproductive failure.

Evaluation of embryo aneuploidy (PGT-A) and endometrial receptivity (ERA) testing in patients with recurrent implantation failure in ICSI cycles

OBJECTIVE

The objective of a study was to assess the ability of the pre-implantation genetic testing of embryos for aneuploidy (PGT-A) and Endometrial receptivity array (ERA)-alone or in combination to improve the clinical outcomes in intracytoplasmic sperm injection (ICSI) cycles in patients with repeated implantation failure (RIF).

METHODS

This was a retrospective study of the 253 cycles with a history of the previous RIF. They were divided into four groups: Group I - frozen embryo transfers without any additional tests or procedures (pure FET), n = 72 cycles; Group II - FET with PGT-A, n = 87; Group III - FET with PGT-A and ERA, n = 72; Group IV - FET with ERA, n = 22.

RESULTS

Median age of the entire study group for the females was 35 years. Only Group II (FET + PGT-A) showed statistically significant higher chance in achieving both biochemical (p = .01, OR = 5.5) and clinical pregnancy (p =.049, OR = 2.3), as compared to the Group I (FET with no additional tests). Both Group III and Group IV failed to demonstrate better clinical outcomes as compared to the Group I.

CONCLUSIONS

Patients with RIF can benefit from testing for embryo aneuploidy using the PGT-A method, but the ability of the ERA test to improve the clinical outcome in ICSI cycles seems to be rather limited. Although the endometrium cycle is also weakened with age, the contribution of the embryo genetic quality is evidently more important for successful implantation, although in principle both factors reflect the reproductive health.

Lactobacillus iners and gasseri, Prevotella bivia and HPV Belong to the Microbiological Signature Negatively Affecting Human Reproduction

Infertile couples undergoing the use of assisted reproductive technology are a good study model to evaluate the microbiological signatures affecting reproductive health. We tested vaginal lavages, follicular fluids, embryo culture mediums, and seminal fluids from 47 couples for their microbiome composition and HPV infection. Twenty-five infertile couples were diagnosed with unexplained infertility, whereas 22 were diagnosed with explained infertility. Lactobacilli were dominant in the vaginal lavages of both patient groups, and the most abundant species was L. iners (CST III), which is linked to a decreased fertility rate. Besides this, L. gasseri—which is known to be associated with oocyte DNA fragmentation and decreased sperm mobility—was identified in the seminal fluids, follicular fluids, and embryo culture media of the unexplained infertility group. Prevotella was increased in the seminal fluids of the explained infertility group, along with HPV-positive seminal fluids: an infection commonly associated with infertility, especially male infertility. Prevotella has been described to negatively affect sperm motility. Taken together, these results suggest that the profiling of the reproductive tract microbiome can add new perspectives to human reproduction.

Menstruation: science and society

Women's health concerns are generally underrepresented in basic and translational research, but reproductive health in particular has been hampered by a lack of understanding of basic uterine and menstrual physiology. Menstrual health is an integral part of overall health because between menarche and menopause, most women menstruate. Yet for tens of millions of women around the world, menstruation regularly and often catastrophically disrupts their physical, mental, and social well-being. Enhancing our understanding of the underlying phenomena involved in menstruation, abnormal uterine bleeding, and other menstruation-related disorders will move us closer to the goal of personalized care. Furthermore, a deeper mechanistic understanding of menstruation-a fast, scarless healing process in healthy individuals-will likely yield insights into a myriad of other diseases involving regulation of vascular function locally and systemically. We also recognize that many women now delay pregnancy and that there is an increasing desire for fertility and uterine preservation. In September 2018, the Gynecologic Health and Disease Branch of the Eunice Kennedy Shriver National Institute of Child Health and Human Development convened a 2-day meeting, "Menstruation: Science and Society" with an aim to "identify gaps and opportunities in menstruation science and to raise awareness of the need for more research in this field." Experts in fields ranging from the evolutionary role of menstruation to basic endometrial biology (including omic analysis of the endometrium, stem cells and tissue engineering of the endometrium, endometrial microbiome, and abnormal uterine bleeding and fibroids) and translational medicine (imaging and sampling modalities, patient-focused analysis of menstrual disorders including abnormal uterine bleeding, smart technologies or applications and mobile health platforms) to societal challenges in health literacy and dissemination frameworks across different economic and cultural landscapes shared current state-of-the-art and future vision, incorporating the patient voice at the launch of the meeting. Here, we provide an enhanced meeting report with extensive up-to-date (as of submission) context, capturing the spectrum from how the basic processes of menstruation commence in response to progesterone withdrawal, through the role of tissue-resident and circulating stem and progenitor cells in monthly regeneration-and current gaps in knowledge on how dysregulation leads to abnormal uterine bleeding and other menstruation-related disorders such as adenomyosis, endometriosis, and fibroids-to the clinical challenges in diagnostics, treatment, and patient and societal education. We conclude with an overview of how the global agenda concerning menstruation, and specifically menstrual health and hygiene, are gaining momentum, ranging from increasing investment in addressing menstruation-related barriers facing girls in schools in low- to middle-income countries to the more recent "menstrual equity" and "period poverty" movements spreading across high-income countries.

Uterine microbiome-low biomass and high expectations†

The existence of different bacterial communities throughout the female reproductive tract has challenged the traditional view of human fetal development as a sterile event. There is still no consensus on what physiological microbiota exists in the upper reproductive tract of the vast majority of women who are not in periods of infection or pregnancy, and the role of bacteria that colonize the upper reproductive tract in uterine diseases or pregnancy outcomes is not well established. Despite published studies and advances in uterine microbiome sequencing, some study aspects-such as study design, sampling method, DNA extraction, sequencing methods, downstream analysis, and assignment of taxa-have not yet been improved and standardized. It is time to further investigate the uterine microbiome to increase our understanding of the female reproductive tract and to develop more personalized reproductive therapies, highlighting the potential importance of using microbiological assessment in infertile patients.

The vaginal microbiome as a predictor for outcome of in vitro fertilization with or without intracytoplasmic sperm injection: a prospective study

STUDY QUESTION

Is the presence or absence of certain vaginal bacteria associated with failure or success to become pregnant after an in vitro fertilization (IVF) or IVF with intracytoplasmic sperm injection (IVF-ICSI) treatment?

SUMMARY ANSWER

Microbiome profiling with the use of interspace profiling (IS-pro) technique enables stratification of the chance of becoming pregnant prior to the start of an IVF or IVF-ICSI treatment.

WHAT IS KNOWN ALREADY

Live-birth rates for an IVF or IVF-ICSI treatment vary between 25 and 35% per cycle and it is difficult to predict who will or will not get pregnant after embryo transfer (ET). Recently, it was suggested that the composition of the vaginal microbiota prior to treatment might predict pregnancy outcome. Analysis of the vaginal microbiome prior to treatment might, therefore, offer an opportunity to improve the success rate of IVF or IVF-ICSI.

STUDY DESIGN, SIZE, DURATION

In a prospective cohort study, 303 women (age, 20-42 years) undergoing IVF or IVF-ICSI treatment in the Netherlands were included between June 2015 and March 2016.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Study subjects provided a vaginal sample before the start of the IVF or IVF-ICSI procedure. The vaginal microbiota composition was determined using the IS-pro technique. IS-pro is a eubacterial technique based on the detection and categorization of the length of the 16S-23S rRNA gene interspace region. Microbiome profiles were assigned to community state types based on the dominant bacterial species. The predictive accuracy of the microbiome profiles for IVF and IVF-ICSI outcome of fresh ET was evaluated by a combined prediction model based on a small number of bacterial species. From this cohort, a model was built to predict outcome of fertility treatment. This model was externally validated in a cohort of 50 women who were undergoing IVF or IVF-ICSI treatment between March 2018 and May 2018 in the Dutch division of the MVZ VivaNeo Kinderwunschzentrum Düsseldorf, Germany.

MAIN RESULTS AND THE ROLE OF CHANCE

In total, the vaginal microbiota of 192 women who underwent a fresh ET could be analysed. Women with a low percentage of Lactobacillus in their vaginal sample were less likely to have a successful embryo implantation. The prediction model identified a subgroup of women (17.7%, n = 34) who had a low chance to become pregnant following fresh ET. This failure was correctly predicted in 32 out of 34 women based on the vaginal microbiota composition, resulting in a predictive accuracy of 94% (sensitivity, 26%; specificity, 97%). Additionally, the degree of dominance of Lactobacillus crispatus was an important factor in predicting pregnancy. Women who had a favourable profile as well as <60% L. crispatus had a high chance of pregnancy: more than half of these women (50 out of 95) became pregnant. In the external validation cohort, none of the women who had a negative prediction (low chance of pregnancy) became pregnant.

LIMITATIONS, REASONS FOR CAUTION

Because our study uses a well-defined study population, the results will be limited to the IVF or IVF-ICSI population. Whether these results can be extrapolated to the general population trying to achieve pregnancy without ART cannot be determined from these data.

WIDER IMPLICATIONS OF THE FINDINGS

Our results indicate that vaginal microbiome profiling using the IS-pro technique enables stratification of the chance of becoming pregnant prior to the start of an IVF or IVF-ICSI treatment. Knowledge of their vaginal microbiota may enable couples to make a more balanced decision regarding timing and continuation of their IVF or IVF-ICSI treatment cycles.

STUDY FUNDING/COMPETING INTEREST(S)

This study was financed by NGI Pre-Seed 2014-2016, RedMedTech Discovery Fund 2014-2017, STW Valorisation grant 1 2014-2015, STW Take-off early phase trajectory 2015-2016 and Eurostars VALBIOME grant (reference number: 8884). The employer of W.J.S.S.C. has in collaboration with ARTPred acquired a MIND subsidy to cover part of the costs of this collaboration project. The following grants are received but not used to finance this study: grants from Innovatie Prestatie Contract, MIT Haalbaarheid, other from Dutch R&D tax credit WBSO, RedMedTech Discovery Fund, (J.D.d.J.). Grants from Ferring (J.S.E.L., K.F., C.B.L. and J.M.J.S.S.), Merck Serono (K.F. and C.B.L.), Dutch Heart Foundation (J.S.E.L.), Metagenics Inc. (J.S.E.L.), GoodLife (K.F.), Guerbet (C.B.L.). R.K. is employed by ARTPred B.V. during her PhD at Erasmus Medical Centre (MC). S.A.M. has a 100% University appointment. I.S.P.H.M.S., S.A.M. and A.E.B. are co-owners of IS-Diagnostics Ltd. J.D.d.J. is co-owner of ARTPred B.V., from which he reports personal fees. P.H.M.S. reports non-financial support from ARTPred B.V. P.H.M.S., J.D.d.J. and A.E.B. have obtained patents `Microbial population analysis' (9506109) and `Microbial population analysis' (20170159108), both licenced to ARTPred B.V. J.D.d.J. and A.E.B. report patent applications `Method and kit for predicting the outcome of an assisted reproductive technology procedure' (392EPP0) and patent `Method and kit for altering the outcome of an assisted reproductive technology procedure' by ARTPred. W.J.S.S.C. received personal consultancy and educational fees from Goodlife Fertility B.V. J.S.E.L. reports personal consultancy fees from ARTPred B.V., Titus Health B.V., Danone, Euroscreen and Roche during the conduct of the study. J.S.E.L. and N.G.M.B. are co-applicants on an Erasmus MC patent (New method and kit for prediction success of in vitro fertilization) licenced to ARTPred B.V. F.J.M.B. reports personal fees from Advisory Board Ferring, Advisory Board Merck Serono, Advisory Board Gedeon Richter and personal fees from Educational activities for Ferring, outside the submitted work. K.F. reports personal fees from Ferring (commercial sponsor) and personal fees from GoodLife (commercial sponsor). C.B.L. received speakers' fee from Ferring. J.M.J.S.S. reports personal fees and other from Merck Serono and personal fees from Ferring, unrelated to the submitted paper. The other authors declare that they have no competing interests.

TRIAL REGISTRATION NUMBER

ISRCTN83157250. Registered 17 August 2018. Retrospectively registered.

The Disordered Vaginal Microbiota Is a Potential Indicator for a Higher Failure of in vitro Fertilization

Infertility is one of the most common reproductive system diseases, and no effective method is available for its treatment. Although in vitro fertilization (IVF) has been widely used to enhance the clinical pregnancy outcome of infertility, the unsatisfied pregnancy rate with unknown reasons is obtained. To identify the possible cause of IVF failure, 555 patients were enrolled in the present study to determine their relevant clinical characteristics and vaginal microbiota. Our results indicated that the age and endometrium thickness significantly affected the pregnancy success rate of pregnant patients (P group) and non-pregnant patients (NP group) receiving IVF, and high values of luteinizing hormone, estrogen and progesterone were observed from P group. Furthermore, the Partial Least Squares Discriminant Analysis (PLS-DA) indicated a different microbial composition in P group and NP group, and a higher microbial abundance had been identified in non-pregnant patients compared with pregnant patients. At phylum level, a higher abundance of Firmicutes and Proteobacteria, and a lower abundance of Actinobacteria, Fusobacteria, and Bacteroidetes were obtained in pregnant patients compared with non-pregnant patients. At genus level, a lower abundance of the probiotic Lactobacillus, and higher abundance of pathogens Gardnerella and Prevotella were identified from non-pregnant patients. Therefore, the disordered microbiota, characterizing by the reduction of probiotics and overgrowth of pathogens in non-pregnant patients, may be used as a potential indicator for a higher IVF failure rate.

The first glimpse of the endometrial microbiota in early pregnancy

Investigation of the microbial community in the female reproductive tract with the use of sequencing techniques has revealed that endometrial samples obtained through a transvaginal catheter are dominated by Lactobacillus species. Dysbiotic changes in the endometrial microbiota may be associated with implantation failure or early spontaneous abortion in patients who undergo assisted reproductive technology treatment. Whether or not there is an endometrial microbiota in early pregnancy is unknown. Herein we describe, the human endometrial microbiota in a patient who subsequently had an 8th week spontaneous clinical miscarriage with euploid embryos in the next cycle and, for the first time, during a successful pregnancy in which the endometrial fluid was sampled at 4 weeks of gestation. The microbial profile found on the endometrial sample before the spontaneous abortion had higher bacterial diversity and lower Lactobacillus abundance than the endometrial fluid from the healthy pregnancy. Functional metagenomics detected different Lactobacillus species between the 2 samples. Lactobacillus crispatus was present in the endometrium before the spontaneous abortion, as were other bacteria involved in dysbiosis, which had an unstable functional pattern characterized by transposases and insertion elements. Lactobacillus iners was the most prevalent microbe found in the endometrium during early pregnancy; its presence was associated with defense mechanisms and basal functions. These novel observations prompt future investigations to understand the potential implications of microbiology on healthy and pathologic human pregnancy.

Does bacterial colonization during embryo transfer have an impact on pregnancy rate in ICSI? : Tunisian preliminary results

INTRODUCTION

Embryos' transfer into the uterine cavity remains a limiting factor in the success of intracytoplasmic sperm injection (ICSI). This study aimed to evaluate the impact of cervico-vaginal colonization on ICSI outcomes.

MATERIEL AND METHODS

Longitudinal, prospective and analytical study, conducted from February 1 st to October 31 st, 2017. On the day of embryos' transfer, patients with the following criteria were included: Age ≤ 40, normal uterine ultrasound and hysteroscopy, first or second attempt of ICSI, use of fresh semen and transfer of at least one good quality embryo. Three samples were done for microbiological analysis: vaginal secretions, cervical mucus and the tip of the transfer catheter.

RESULTS

The study included 40 patients. Pregnancy rate was 52.5 %. Catheter contamination occurred in nine cases (22.5 %). The most frequently isolated bacteria were Streptococcus anginosus (37 % of cases), Gardnerella vaginalis (27 % of cases) and Streptococcus agalactiae (18 % of cases). In all cases of contamination, the same bacteria were found also in the vagina and cervical mucus. In cases of contamination with Gardnerella vaginalis, the study of vaginal flora showed bacterial vaginosis. No pregnancy was obtained when contamination of the transfer catheter occurred. In the absence of contamination, pregnancy rate was 61.2 % (ρ = 0.003). Both populations (patients with catheter contamination and patients without catheter contamination) were comparable regarding epidemiological characteristics and ICSI attempt data.

CONCLUSION

Contamination of the transfer catheter by cervical-vaginal bacteria appears to affect IVF results. Systematic antibiotic prophylaxis could be proposed to reduce this negative impact.

Taxonomical and Functional Assessment of the Endometrial Microbiota in A Context of Recurrent Reproductive Failure: A Case Report

Investigation of the microbial community in the female reproductive tract has revealed that the replacement of a community dominated by Lactobacillus with pathogenic bacteria may be associated with implantation failure or early spontaneous abortion in patients undergoing assisted reproductive technology (ART) treatment. Herein we describe taxonomically and functionally the endometrial microbiome of an infertile patient with repeated reproductive failures (involving an ectopic pregnancy and two clinical miscarriages). The microbiological follow-up is presented over 18-month in which the microbiota was evaluated in six endometrial fluid samples. The microbial profile of 16S rRNA gene sequencing showed a persistent infection with Gardnerella and other bacterial taxa such as Atopobium and Bifidobacterium. In addition, taxonomic and functional analysis by whole metagenome sequencing in the endometrial fluid sample collected before one clinical miscarriage suggested the presence of multiple Gardnerella vaginalis clades with a greater abundance of clade 4, usually associated with metronidazole resistance. These results revealed a persistent G. vaginalis endometrial colonization presenting genetic features consistent with antimicrobial resistance, biofilm formation, and other virulence factors, which could be related to the reproductive failure observed.

Relevance of assessing the uterine microbiota in infertility

Technical advances in massive parallel sequencing have allowed the characterization of the whole reproductive tract microbiome in all the compartments beyond the vagina. The microbiota in the uterine cavity seem to be a continuum from the microbiota in the vagina, but several works have reported significant differences between vaginal and endometrial microbiota, highlighting the relevance of assessing the upper genital tract microbiota to better understand the potential roles of bacteria in the physiological and pathological processes taking place in the uterine cavity, including embryo implantation, pregnancy maintenance, and other gynecological diseases. However, the study of the endometrial microbiota, as with other low-biomass microbiota, presents important hurdles because, due to the small amount of starting material, they are easily contaminated by exogenous bacterial DNA. For this reason, careful and appropriate investigation of the endometrial microbiota is of outstanding importance to detect uterine dysbiosis that may impact the reproductive function.

How uterine microbiota might be responsible for a receptive, fertile endometrium

BACKGROUND

Fertility depends on a receptive state of the endometrium, influenced by hormonal and anatomical adaptations, as well as the immune system. Local and systemic immunity is greatly influenced by microbiota. Recent discoveries of 16S rRNA in the endometrium and the ability to detect low-biomass microbiota fueled the notion that the uterus may be indeed a non-sterile compartment. To date, the concept of the 'sterile womb' focuses on in utero effects of microbiota on offspring and neonatal immunity. However, little awareness has been raised regarding the importance of uterine microbiota for endometrial physiology in reproductive health; manifested in fertility and placentation.

OBJECTIVE AND RATIONALE

Commensal colonization of the uterus has been widely discussed in the literature. The objective of this review is to outline the possible importance of this uterine colonization for a healthy, fertile uterus. We present the available evidence regarding uterine microbiota, focusing on recent findings based on 16S rRNA, and depict the possible importance of uterine colonization for a receptive endometrium. We highlight a possible role of uterine microbiota for host immunity and tissue adaptation, as well as conferring protection against pathogens. Based on knowledge of the interaction of the mucosal immune cells of the gut with the local microbiome, we want to investigate the potential implications of commensal colonization for uterine health.

SEARCH METHODS

PubMed and Google Scholar were searched for articles in English indexed from 1 January 2008 to 1 March 2018 for '16S rRNA', 'uterus' and related search terms to assess available evidence on uterine microbiome analysis. A manual search of the references within the resulting articles was performed. To investigate possible functional contributions of uterine microbiota to health, studies on microbiota of other body sites were additionally assessed.

OUTCOMES

Challenging the view of a sterile uterus is in its infancy and, to date, no conclusions on a 'core uterine microbiome' can be drawn. Nevertheless, evidence for certain microbiota and/or associated compounds in the uterus accumulates. The presence of microbiota or their constituent molecules, such as polysaccharide A of the Bacteroides fragilis capsule, go together with healthy physiological function. Lessons learned from the gut microbiome suggest that the microbiota of the uterus may potentially modulate immune cell subsets needed for implantation and have implications for tissue morphology. Microbiota can also be crucial in protection against uterine infections by defending their niche and competing with pathogens. Our review highlights the need for well-designed studies on a 'baseline' microbial state of the uterus representing the optimal starting point for implantation and subsequent placenta formation.

WIDER IMPLICATIONS

The complex interplay of processes and cells involved in healthy pregnancy is still poorly understood. The correct receptive endometrial state, including the local immune environment, is crucial not only for fertility but also placenta formation since initiation of placentation highly depends on interaction with immune cells. Implantation failure, recurrent pregnancy loss, and other pathologies of endometrium and placenta, such as pre-eclampsia, represent an increasing societal burden. More robust studies are needed to investigate uterine colonization. Based on current data, future research needs to include the uterine microbiome as a relevant factor in order to understand the players needed for healthy pregnancy.

Deciphering the effect of reproductive tract microbiota on human reproduction

BACKGROUND

The female reproductive tract contains an active microbiome comprising mainly bacteria from the Lactobacillus genus, which is associated with a healthy microbiome state. However, spatio-temporal fluctuations of this microbiome that occur in response to internal and external factors may impact the physiology of the reproductive tract organs and even lead to pathological states.

METHODS

Current literature covering the reproductive tract microbiome is summarized and contextualized in this review.

MAIN FINDINGS

This review presents the current knowledge about the bacterial composition of the lower and upper reproductive tract as well as the impact of the microbiota on women's health and reproduction. We place special focus on the impact of the endometrial microbiome in infertility and assisted reproductive technologies.

CONCLUSION

The assessment of the reproductive tract microbiome adds a new microbiological perspective to human reproduction, pregnancy, and onset of new life, highlighting the importance of considering the evaluation of microbial communities to improve personalized care in reproductive medicine and women's health.

Impact of asymptomatic genital tract infections on in vitro Fertilization (IVF) outcome

Background

Infertility is estimated to affect approximately 9–30% of reproductive-aged couples. Several conditions involving one or both partners may contribute to infertility. The aim of this study is to evaluate the role of asymptomatic genital tract infections in the outcome of In Vitro Fertilization (IVF) in couples with infertility.

Methods

A total of 285 infertile couples were enrolled in the study. Vaginal/endocervical swabs and semen samples were collected and subjected to microbiological analysis. Spermiograms were carried out on semen specimens, and lactobacilli were quantified in vaginal swabs. Data were associated with IVF results and analysed by using non parametric tests and multivariate analysis.

Results

Microbiological analysis showed that 46.3% of couples presented with an asymptomatic genital tract infection. Spermiogram results showed a significantly diminished motility of sperm cells in samples positive to microbiological testing compared to negative specimens. Enterococcus faecalis was the most prevalent species (11.6%) in positive semen samples and was found to negatively affect both sperm morphology (p = 0.026) and motility (p = 0.003). Analysis of genital swabs from females showed that the presence of E. faecalis (p<0.0001), Escherichia coli (p = 0.0123), Streptococcus agalactiae (p<0.0001), and Gardnerella vaginalis (p = 0.0003) was significantly associated to reduced levels of vaginal lactobacilli. Association of microbiological data with IVF outcome showed that 85.7% of IVF+ couples was microbiologically negative, while IVF was successful in just 7.5% of couples infected with E. faecalis and/or U. urealyticum and/or M. hominis (p = 0.02).

Conclusions

The results show the negative impact of E. faecalis on sperm quality and the association of definite bacterial pathogens with reduced levels of vaginal lactobacilli. The presence of E. faecalis and/or U. urealyticum and/or M. hominis in genital samples of infertile couples is predictive for a negative outcome of IVF.

Endometrial microbes and microbiome: Recent insights on the inflammatory and immune "players" of the human endometrium

In recent years, extended scientific works shed light on the important role played by the endometrium in early pregnancy. This review examines our current knowledge about the delicate balance between microbial and cellular immune agents at endometrial level: All of them might affect endometrial receptivity. In contrast to the classical thinking of human endometrium as a sterile tissue, several recent studies have drawn attention to a resident population of microorganisms, which reaches only a 30% of concordance with those of the cervical-vaginal flora. At present, the understanding of the microbiome in relation to human reproduction is in its infancy and further studies are needed to clarify the activity of endometrial microbiome and the possible effects of a "reproductive tract dysbiosis" on fertility. Moreover, in the human endometrium, there is a complex system works preventing the risk of infection as well as enabling, when pregnancy occurs, the acceptance of the blastocyst. In this way, the endometrium plays a central role in the uterine immune surveillance. A better understanding of the different agents that may affect endometrial receptivity would improve the diagnosis and treatment of obstetric complications related to defective implantation and placentation.

Cervical mucus removal prior to intrauterine insemination: a randomized trial

OBJECTIVE

To detect if removing the cervical mucus before performing intrauterine insemination (IUI) could improve pregnancy outcomes in patients with unexplained infertility.

DESIGN

Prospective randomized study.

SETTING

An Egyptian University Hospital.

POPULATION

Seven hundred and fourteen couples with unexplained infertility who underwent intrauterine insemination (IUI) with or without cervical mucus removal.

METHODS

Using computer-generated numbers, patients were randomly allocated to cervical-mucus-removal (removed from both internal and external os) or non-mucus-removal groups. Only participants were blinded as to group assignment.

MAIN OUTCOME MEASURES

The clinical pregnancy rate.

RESULTS

Of 714 IUI patients between November 2014 and March 2017, 361 were in the mucus removal group, and 353 in the non-mucus-removal group. Difficult catheterization was encountered in 17 cases out of 666 (2.6%) 12 in the cervical-mucus-removal group and five in the non-mucus-removal group). A total of 666 IUI cycles were completed while 48 were either cancelled or lost in their follow-up. The clinical pregnancy rate was significantly higher in the mucus-removal group [31.0% (n = 112)] than in the non-mucus-removal group [21.8% (n = 77); P = 0.005]. Ovarian hyperstimulation developed in 33 (4.6%) cases: 18 cervical mucus-removal and 15 non-mucus-removal. All except one were mild and managed with outpatient care.

CONCLUSIONS

Cervical mucus removal before IUI could improve pregnancy outcomes in women with unexplained infertility.

TWEETABLE ABSTRACT

Cervical mucus removal before IUI can improve pregnancy outcomes.

Evidence that the endometrial microbiota has an effect on implantation success or failure

BACKGROUND

Bacterial cells in the human body account for 1-3% of total body weight and are at least equal in number to human cells. Recent research has focused on understanding how the different bacterial communities in the body (eg, gut, respiratory, skin, and vaginal microbiomes) predispose to health and disease. The microbiota of the reproductive tract has been inferred from the vaginal bacterial communities, and the uterus has been classically considered a sterile cavity. However, while the vaginal microbiota has been investigated in depth, there is a paucity of consistent data regarding the existence of an endometrial microbiota and its possible impact in reproductive function.

OBJECTIVE

This study sought to test the existence of an endometrial microbiota that differs from that in the vagina, assess its hormonal regulation, and analyze the impact of the endometrial microbial community on reproductive outcome in infertile patients undergoing in vitro fertilization.

STUDY DESIGN

To identify the existence of an endometrial microbiota, paired samples of endometrial fluid and vaginal aspirates were obtained simultaneously from 13 fertile women in prereceptive and receptive phases within the same menstrual cycle (total samples analyzed n = 52). To investigate the hormonal regulation of the endometrial microbiota during the acquisition of endometrial receptivity, endometrial fluid was collected at prereceptive and receptive phases within the same cycle from 22 fertile women (n = 44). Finally, the reproductive impact of an altered endometrial microbiota in endometrial fluid was assessed by implantation, ongoing pregnancy, and live birth rates in 35 infertile patients undergoing in vitro fertilization (total samples n = 41) with a receptive endometrium diagnosed using the endometrial receptivity array. Genomic DNA was obtained either from endometrial fluid or vaginal aspirate and sequenced by 454 pyrosequencing of the V3-V5 region of the 16S ribosomal RNA (rRNA) gene; the resulting sequences were taxonomically assigned using QIIME. Data analysis was performed using R packages. The χ² test, Student t test, and analysis of variance were used for statistical analyses.

RESULTS

When bacterial communities from paired endometrial fluid and vaginal aspirate samples within the same subjects were interrogated, different bacterial communities were detected between the uterine cavity and the vagina of some subjects. Based on its composition, the microbiota in the endometrial fluid, comprising up to 191 operational taxonomic units, was defined as a Lactobacillus-dominated microbiota (>90% Lactobacillus spp.) or a non-Lactobacillus-dominated microbiota (<90% Lactobacillus spp. with >10% of other bacteria). Although the endometrial microbiota was not hormonally regulated during the acquisition of endometrial receptivity, the presence of a non-Lactobacillus-dominated microbiota in a receptive endometrium was associated with significant decreases in implantation [60.7% vs 23.1% (P = .02)], pregnancy [70.6% vs 33.3% (P = .03)], ongoing pregnancy [58.8% vs 13.3% (P = .02)], and live birth [58.8% vs 6.7% (P = .002)] rates.

CONCLUSION

Our results demonstrate the existence of an endometrial microbiota that is highly stable during the acquisition of endometrial receptivity. However, pathological modification of its profile is associated with poor reproductive outcomes for in vitro fertilization patients. This finding adds a novel microbiological dimension to the reproductive process.

Does screening for vaginal infection have an impact on pregnancy rates in intracytoplasmic sperm injection cycles?

Objective:

Assisted reproduction techniques have become widespread worldwide. Considering their costs, physicians endeavor to improve pregnancy rates. Infections are one of the disrupting problems in this arena. We aimed to investigate the effects of screening for vaginal infection on pregnancy rates in intracytoplasmic sperm injection cycles.

Materials and Methods:

One hundred twenty patients randomized into two groups for this study. Patients were screened for vaginal infections in group 1, and no screening was performed in group 2. The assisted reproduction outcomes were investigated and compared between the two groups.

Results:

There was no significant difference between ages, or durations and causes of infertility of patients who conceived and of those who did conceive. Forty-five patients in group 1, and 40 patients in group 2 reached the embryo transfer stage. The rates of conception were 23.5% (n=4) in culture-positive patients (n=17), and 42.9% (n=12) in culture-negative patients (n=28) in group 1. There was no significant difference among patients who were not screened, screen-positive, and screen-negative, in terms of pregnancy rates. None of the patients had Neisseria gonorrhoeae or Trichomonas vaginalis. Bacterial vaginosis was detected in 13 patients, and both bacterial vaginosis and Chlamydia trachomatis were detected in 4 patients. Three of 4 patients who conceived screen-positive and 8 of 12 patients who conceived screen-negative delivered healthily at term.

Conclusion:

No significant difference was found between patients who were sampled for culture and patients who were not sampled in terms of pregnancy rates. Also, no difference was found between the patients who were culture-negative and patients who were treated with antimicrobials after a culture positive result. Further larger studies are warranted to clarify this issue.

Antibiotic Prophylaxis for Gynecologic Procedures prior to and during the Utilization of Assisted Reproductive Technologies: A Systematic Review

The use of assisted reproductive technologies (ART) has increased steadily. There has been a corresponding increase in the number of ART-related procedures such as hysterosalpingography (HSG), saline infusion sonography (SIS), hysteroscopy, laparoscopy, oocyte retrieval, and embryo transfer (ET). While performing these procedures, the abdomen, upper vagina, and endocervix are breached, leading to the possibility of seeding pelvic structures with microorganisms. Antibiotic prophylaxis is therefore important to prevent or treat any procedure-related infections. After careful review of the published literature, it is evident that routine antibiotic prophylaxis is generally not recommended for the majority of ART-related procedures. For transcervical procedures such as HSG, SIS, hysteroscopy, ET, and chromotubation, patients at risk for pelvic infections should be screened and treated prior to the procedure. Patients with a history of pelvic inflammatory disease (PID) or dilated fallopian tubes are at high risk for postprocedural infections and should be given antibiotic prophylaxis during procedures such as HSG, SIS, or chromotubation. Antibiotic prophylaxis is recommended prior to oocyte retrieval in patients with a history of endometriosis, PID, ruptured appendicitis, or multiple prior pelvic surgeries.

Individualized medicine and the microbiome in reproductive tract

Humans have evolved along with the millions of microorganisms that populate their bodies. These microbes (10(14)) outnumber human cells by 10 to 1 and account for 3 × 10(6) genes, more than ten times the 25,000 human genes. This microbial metagenome acts as our "other genome" and like our own genes, is unique to the individual. Recent international efforts such as the Human Microbiome Project (HMP) and the MetaHIT Project have helped catalog these microbial genomes using culture-independent, high-throughput, next-generation sequencing. This manuscript will describe recent efforts to define microbial diversity in the female reproductive tract because of the impact that microbial function has on reproductive efficiency. In this review, we will discuss current evidence that microbial communities are critical for maintaining reproductive health and how perturbations of microbial community structures can impact reproductive health from the aspect of infection, reproductive cyclicity, pregnancy, and disease states. Investigations of the human microbiome are propelling interventional strategies from treating medical populations to treating individual patients. In particular, we highlight how understanding and defining microbial community structures in different disease and physiological states have lead to the discovery of biomarkers and, more importantly, the development and implementation of microbial intervention strategies (probiotics) into modern day medicine. Finally this review will conclude with a literature summary of the effectiveness of microbial intervention strategies that have been implemented in animal and human models of disease and the potential for integrating these microbial intervention strategies into standard clinical practice.