Prevalence of vaginal microorganisms among pregnant women according to trimester and association with preterm birth

Impact of pre-pregnancy weight on the risk of premature rupture of membranes in Chinese women

Objective

The objective of this study was to investigate the influence of pre-pregnancy body mass index (BMI) on the incidence of premature rupture of membranes (PROM) among Chinese women.

Methods

This was a hospital-based retrospective cohort study of 75,760 Chinese women who had live singleton births between 2016 and 2020. In this study, we utilized logistic regression analysis to estimate the association between pre-pregnancy BMI and PROM based on gestational age.

Results

Prior to pregnancy, being overweight or obese was found to be significantly associated with an increased risk of preterm premature rupture of membranes (PPROM), as evidenced by adjusted odds ratios and 95 % confidence intervals of 1.336 (1.173-1.522) and 1.411 (1.064-1.872), respectively. Those with PPROM were divided into three groups according to gestational age: 22-27, 28-31, and 32-36 weeks. Women who were overweight or obese prior to pregnancy had a higher likelihood of experiencing PROM between 22 and 27 weeks of gestation. This finding remained consistent even after controlling for potential confounding factors, such as gestational diabetes mellitus (GDM), gestational hypertension, preeclampsia, hydramnios, cervical abnormalities, and a history of preterm birth.

Conclusion

Our research findings indicate that being overweight or obese before pregnancy is linked to a higher likelihood of experiencing PPROM. Therefore, achieving optimal weight before pregnancy is important to prevent PPROM and its associated complications.

The effects of microbiota on reproductive health: A review

Reproductive issues are becoming an increasing global problem. There is increasing interest in the relationship between microbiota and reproductive health. Stable microbiota communities exist in the gut, reproductive tract, uterus, testes, and semen. Various effects (e.g., epigenetic modifications, nervous system, metabolism) of dysbiosis in the microbiota can impair gamete quality; interfere with zygote formation, embryo implantation, and embryo development; and increase disease susceptibility, thus adversely impacting reproductive capacity and pregnancy. The maintenance of a healthy microbiota can protect the host from pathogens, increase reproductive potential, and reduce the rates of adverse pregnancy outcomes. In conclusion, this review discusses microbiota in the male and female reproductive systems of multiple animal species. It explores the effects and mechanisms of microbiota on reproduction, factors that influence microbiota composition, and applications of microbiota in reproductive disorder treatment and detection. The findings support novel approaches for managing reproductive diseases through microbiota improvement and monitoring. In addition, it will stimulate further systematic explorations of microbiota-mediated effects on reproduction.

Vaginal microecological characteristics of women in different physiological and pathological period

The vaginal microbiota, the host endocrine system, the vaginal anatomy, and the local mucosal immunity comprise the vaginal microbiota, which interacts with each other to maintain the balance of the vaginal microbiota, which maintains female reproductive health. Puberty, menstruation, pregnancy, and menopause are four phases women go through during their reproductive and post-reproductive years. Vaginal microbiota composition and abundance are heavily influenced by estrogen and progesterone, which start at puberty and continue during the reproductive years in a dynamic balance with some fluctuations. Estrogen promotes proliferation of vaginal epithelial cells and increases glycogen storage, while progesterone lyses vaginal epithelial cells, facilitating the release of glycogen to maintain normal pH. This review summarizes the latest national and international evidence on the composition and distribution of vaginal microecology in women during different physiological and pathological periods and proposes a hormone-driven microbial diversity hypothesis to explain the temporal patterns of vaginal microbial diversity during the female reproductive cycle and menopause. A relatively balanced vaginal microecological system has a positive effect on the maintenance of female health. An imbalance in the ratio of flora can lead to susceptibility to infections or reproductive complications. The study of human microecology and its role in the development and progression of human disease is essential for the prevention, diagnosis, and treatment of related obstetric and gynecologic conditions.

Phylogeny-guided microbiome OTU-specific association test (POST)

BACKGROUND

The relationship between host conditions and microbiome profiles, typically characterized by operational taxonomic units (OTUs), contains important information about the microbial role in human health. Traditional association testing frameworks are challenged by the high dimensionality and sparsity of typical microbiome profiles. Phylogenetic information is often incorporated to address these challenges with the assumption that evolutionarily similar taxa tend to behave similarly. However, this assumption may not always be valid due to the complex effects of microbes, and phylogenetic information should be incorporated in a data-supervised fashion.

RESULTS

In this work, we propose a local collapsing test called phylogeny-guided microbiome OTU-specific association test (POST). In POST, whether or not to borrow information and how much information to borrow from the neighboring OTUs in the phylogenetic tree are supervised by phylogenetic distance and the outcome-OTU association. POST is constructed under the kernel machine framework to accommodate complex OTU effects and extends kernel machine microbiome tests from community level to OTU level. Using simulation studies, we show that when the phylogenetic tree is informative, POST has better performance than existing OTU-level association tests. When the phylogenetic tree is not informative, POST achieves similar performance as existing methods. Finally, in real data applications on bacterial vaginosis and on preterm birth, we find that POST can identify similar or more outcome-associated OTUs that are of biological relevance compared to existing methods.

CONCLUSIONS

Using POST, we show that adaptively leveraging the phylogenetic information can enhance the selection performance of associated microbiome features by improving the overall true-positive and false-positive detection. We developed a user friendly R package POSTm which is freely available on CRAN ( https://CRAN.R-project.org/package=POSTm ). Video Abstract.

Antibiotic-resistant pathogenic bacterial isolates from patients attending the outpatient department of university of Cape Coast hospital, Ghana: A retrospective study between 2013-2015

Uropathogenic Escherichia coli (E. coli) is an important urinary tract infection (UTI) that has been associated with both complicated and uncomplicated disease conditions. The global emergence of multiple drug-resistant (MDR) and extended-spectrum β-lactamase (ESBL) is of public health concern as the resistance limits the current treatment options. The objective of this study was to analyze the antibiotic-resistant patterns among the uropathogenic E. coli isolates at the University of Cape Coast (UCC) hospital between 2013 and 2015 as baseline data to understand the current antibiotic resistance situation within UCC and its environs. A retrospective cross-sectional study of bacteria isolates at UCC hospital from January 2013 to December 2015 were analyzed. A standard biochemical and antibiotic susceptibility tests were performed using Kirby-Bauer NCCLs modified disc diffusion technique. The network of interaction between pathogenic isolates and antibiotic resistance was performed using Cytoscape software. Statistical significance was tested using ANOVA and one-sample Wilcoxon test. The overall E. coli prevalence was 15.76% (32/203); females had the highest infection of 17.33% (26/150) compared to male subjects who had 11.32% (6/53) out of all the pathogenic infections. The E. coli prevalence among the age categories were 2/21 (9.52%), 27/154 (17.53%) and 4/21 (19.05%) among ≤20 years, 21-40 years and 41-60 years respectively. The isolated resistant pathogens exhibited different antibiotic resistance patterns. An interaction network of nodes connecting to other nodes indicating positive correlations between the pathogens and antibiotic resistance was established. Escherichia coli, Citrobacter spp, Klebsiella spp among other isolated pathogens formed higher centrality in the network of interaction with antibiotic resistance. The individual E. coli isolates showed a significant difference in the mean ± SD (95% CI) pattern of antibiotic resistance, 2.409±1.205 (1.828-2.990), χ2 = 36.68, p<0.0001. In conclusion, the study reports the interaction of E. coli isolates at UCC hospital and its antibiotic-resistant status between 2013 and 2015. This data forms the baseline information for assessing the current antibiotic status in UCC and its environs.

Prevalence of bacterial vaginosis and aerobic vaginitis and their associated risk factors among pregnant women from northern Ethiopia: A cross-sectional study

This study aimed to determine the prevalence of bacterial vaginosis (BV) and aerobic vaginitis (AV) and their associated risk factors among pregnant women from Ethiopia. Also, this study investigated the bacterial pathogens and their antibiotic resistance in AV cases. A total of 422 pregnant women from northern Ethiopia were participated in this study. Socio-demographic and clinical data were recorded. Vaginal swabs were collected and used for wet mount and Gram stain methods to evaluate the AV and BV scores according to the Nugent’s and Donder’s criteria, respectively. In AV cases the bacterial pathogens and their antibiotic resistance were determined using standard methods. The possible risk factors for AV and BV in pregnant women were investigated. The prevalence rates of BV and AV were 20.1% (85/422) and 8.1% (34/422), respectively. BV was more common in symptomatic vs. asymptomatic people (P < 0.001), and in second trimester vs. first trimester samples (P = 0.042). However, AV was more common in secondary school vs. primary and those who were unable to read and write (P = 0.021) and in housewife women vs. employee (P = 0.013). A total of 44 bacterial strains were isolated from AV cases, of which the coagulase-negative staphylococci (CoNS) (38.6%) and Staphylococcus aureus (29.5%) were the most predominant bacteria, respectively. The highest resistance rate was observed against penicillin (100.0%) in staphylococci, while 86.7% of them were sensitive to ciprofloxacin. The resistance rate of Enterobacteriaceae ranged from 0.0% for ciprofloxacin and chloramphenicol to 100.0% against amoxicillin/clavulanate. The prevalence of BV was higher than AV in pregnant women. This higher prevalence of BV suggests that measures should be taken to reduce the undesired consequences related to BV in the pregnancy. The circulation of drug-resistant bacteria in vaginal infections requires a global surveillance to reduce the risks to pregnant mothers and infants.

Influence of Maternal Microbiome and Inflammatory Response in Preterm Birth: Recent Aspects of the Prevention of Preterm Birth

Preterm birth (PTB) is a global health issue and one of the most challenging problems affecting 12.9 million births worldwide. PTB is a multi-etiological disease and remains incompletely understood. The major cause of PTB is infection or inflammation and disruption of the vaginal microbiome, which affects the maternal immunologic response leading to PTB. The vaginal microbiome composition changes by a shift in the community are typically dominated by Lactobacillus during pregnancy. There are complex interactions between the maternal microbiome in pregnancy and the development of PTB, therefore, researchers have struggled to connect the maternal microbiome with the dysregulation of the maternal immune response in cases of PTB. The host microbiome affects alterations of the microorganisms with external stimuli such as disease, nutrition, immunity, and behavior. In this review, we discuss the complex association between the maternal microbiome and the risk of PTB and also focus on recent aspects of the prevention of PTB.

Vaginal health in women and the possibility of predicting preterm birth through microbiome analysis

Background: With the recent development of next-generation sequencing technology, the microbiome in the body is being revealed in detail. It is also possible to describe the normal vaginal microenvironment and, more specifically, any changes in pregnancy. Moreover, we present the hypothesis that the microbiome is a contributing factor to preterm birth (PTB).Current Concepts: High estrogen status stimulates the maturation and proliferation of vaginal epithelial cells and the accumulation of glycogen, which promotes lactic acid production and maintains the vaginal environment at an acidic pH. The vaginas of most premenopausal women are predominantly colonized by Lactobacillus which plays an important role in local defense. Recently, it has also been reported that there are several specific types of Lactobacillus species, while other anaerobes, including Gardnerella and Atopobium also coexist in the vagina. Vaginal dysbiosis is defined as various expressions of microorganisms, secretion of specific metabolites, and changes in pH. During pregnancy, a multitude of microbiome changes occur in the oral cavity, gut, vagina, and placenta. The risk of PTB increases if the microbiome changes to one of dysbiosis. It is possible to analyze the characteristic microbiome composition related to PTB and to develop biomarkers predicting PTB. It is necessary to educate patients based on these findings.Discussion and Conclusion: Microbiome analysis has contributed significantly to understanding the association between women’s vaginal health and PTB. Continued research will also contribute to public health by assisting in the prediction and prevention of PTB.

Colonization Rate of Potential Neonatal Disease-Causing Bacteria, Associated Factors, and Antimicrobial Susceptibility Profile Among Pregnant Women Attending Government Hospitals in Hawassa, Ethiopia

Introduction

Vaginal colonization with some species of bacteria during the last term of pregnancy can affect the health of fetuses and newborns resulting in high morbidity and mortality among newborns.

Objective

The aim of this study was to determine the colonization rate of potential neonatal disease-causing bacteria, factors associated with colonization rate, and the antimicrobial susceptibility profile of bacteria among pregnant women.

Methods

Institution-based cross-sectional study was conducted on pregnant women from October 13 to December 28, 2020, at government hospitals located in Hawassa, Ethiopia. Background data were captured using a structured questionnaire. Vaginal swabs were collected to isolate bacteria using the standard method. Antimicrobial susceptibility test was performed using the modified Kirby–Bauer disc diffusion method. Data were analyzed using SPSS. Factors that could predict vaginal colonization with potential neonatal disease-causing bacteria were determined using logistic regression.

Results

Overall bacterial colonization rate among pregnant women was 271 (98.9%) 95 CI (97.4‒100.1). The prevalence of potential neonatal disease-causing bacteria was 95 (34.7%) 95 CI (28.8‒40.1). The proportion of potential neonatal disease-causing bacteria were as follows: Escherichia coli (n=82, 29.9%), Acinetobacter species (n=9, 3.3%), Staphylococcus aureus (n=7. 2.6%), and Klebsiella pneumoniae (n=4, 1.5%). Pregnant women with a gestational age of 38‒40 weeks were 1.9 times (AOR= 1.9, 95% CI= 1.0–3.4, p=0.04) were more likely to be colonized by potential neonatal disease-causing bacteria. All E. coli, Klebsiella species, and Acinetobacter species were susceptible to gentamicin and imipenem. All S. aureus were susceptible to penicillin, tetracycline, clindamycin, and erythromycin.

Conclusion

High proportion of pregnant women in this study were colonized with potential neonatal disease-causing bacteria. E. coli was the predominant bacteria. Most bacteria isolated in this study were susceptible to antimicrobial agents tested. Gestational age was significantly associated with the colonization rate of potential neonatal disease-causing bacteria.

Molecular Mechanism of Microbiota Metabolites in Preterm Birth: Pathological and Therapeutic Insights

Preterm birth (PTB) refers to the birth of infants before 37 weeks of gestation and is a challenging issue worldwide. Evidence reveals that PTB is a multifactorial dysregulation mediated by a complex molecular mechanism. Thus, a better understanding of the complex molecular mechanisms underlying PTB is a prerequisite to explore effective therapeutic approaches. During early pregnancy, various physiological and metabolic changes occur as a result of endocrine and immune metabolism. The microbiota controls the physiological and metabolic mechanism of the host homeostasis, and dysbiosis of maternal microbial homeostasis dysregulates the mechanistic of fetal developmental processes and directly affects the birth outcome. Accumulating evidence indicates that metabolic dysregulation in the maternal or fetal membranes stimulates the inflammatory cytokines, which may positively progress the PTB. Although labour is regarded as an inflammatory process, it is still unclear how microbial dysbiosis could regulate the molecular mechanism of PTB. In this review based on recent research, we focused on both the pathological and therapeutic contribution of microbiota-generated metabolites to PTB and the possible molecular mechanisms.

Identification of Indicators for Preterm Birth Using Retinoid Metabolites

Metabolites reflect the biochemical dynamics for the maintenance of pregnancy and parturition. UPLC-Q/TOF-MS and LC-MS/MS metabolomics were performed to identify and validate the plasma metabolomic signatures of preterm birth (PTB). We recruited pregnant women between 16 and 40 weeks 5 days gestational age at Ewha Womans Mokdong Hospital for a nested case-control study. In untargeted UPLC-Q/TOF-MS, score plots of partial least-squares discriminant analysis clearly separated the PTB group from the term birth (TB, n = 10; PTB, n = 11). Fifteen metabolites were significantly different between the two groups, as indicated by a variable importance in projection >1 and p < 0.05. Metabolic pathways involving retinol, linoleic acid, d-arginine, and d-ornithine were associated with PTB. Verification by LC-MS/MS focused on retinol metabolism (TB, n = 39; PTB, n = 20). Retinol levels were significantly reduced in PTB compared to TB, while retinal palmitate, all-trans-retinal, and 13-cis-retinoic acid (¹³cis-RA) significantly increased (p < 0.05). Retinol-binding protein levels were also elevated in PTB. Additionally, all-trans-retinal (AUC 0.808, 95% CI: 0.683–0.933) and ¹³cis-RA (AUC 0.826, 95% CI: 0.723–0.930) showed improved predictions for PTB-related retinol metabolites. This study suggests that retinoid metabolism improves the accuracy of PTB predictions and plays an important role in maintaining pregnancy and inducing early parturition.

Comparative metagenomic analysis of the vaginal microbiome in healthy women

The composition of these vaginal microbiome has a significant impact on women's health. However, few studies have characterized the vaginal microbiome of healthy Chinese women using metagenomic sequencing. Here, we carried out a comparative metagenomic analysis to survey taxonomic, functional levels, and microbial communities' genome content in healthy women's vaginal microbiome. Overall, we observed a total of 111 species, including all dominant vaginal Lactobacillus species, such as L. iners, L. crispatus, L. gasseri, and L. jensenii. Unlike microbial taxa, several pathways were ubiquitous and prevalent across individuals, including adenosine ribonucleotides de novo biosynthesis and pyruvate fermentation to acetate and lactate II. Notably, our diversity analysis confirmed a significant difference in healthy women from different ethnic groups. Moreover, we binned vaginal assemblies into 62 high-quality genomes, including 9 L. iners, 7 A. vaginae, 5 L. jensenii, and 5 L. crispatus. We identified the pan and core genomes of L. iners and A. vaginae and revealed the genetic diversity. Primary differences between strains were the hypothetical genes and mobile element-like genes. Our results provide a framework for understanding the implications of the female reproductive tract's composition and functional potential and highlight the importance of genome-resolved metagenomic analysis to further understand the human vaginal microbiome.

Relationship between vaginal group B streptococcus colonization in the early stage of pregnancy and preterm birth: a retrospective cohort study

BACKGROUND

Although infection and inflammation within the genital tract during pregnancy is considered a major risk factor for spontaneous preterm birth (PTB), there are few studies on association between vaginal microorganisms in the early stage of pregnancy and PTB. The aim of this study was to investigate relationship between vaginal Group B streptococcus (GBS) colonization, a leading cause of infection during pregnancy, in the early stage of pregnancy and PTB.

METHODS

This single-center, retrospective cohort study utilized data from 2009 to 2017 obtained at TOYOTA Memorial Hospital. Women with singleton pregnancies who underwent vaginal culture around 14 weeks of gestation during their routine prenatal check-up were included. Vaginal sampling for Gram staining and culture was performed regardless of symptoms. GBS colonization was defined as positive for GBS latex agglutination assay. Statistical analysis was performed to determine the factors associated with PTB.

RESULTS

Overall 1079 singleton pregnancies were included. GBS (5.7%) and Candida albicans (5.5%) were the most frequently observed microorganisms. The incidence of PTB (before 34 and before 37 weeks of gestation) were significantly higher in the GBS-positive group than in the GBS-negative group (6.6% vs 0.5%, p = 0.001 and 9.8% vs 4.3%, p = 0.047). Our multivariable logistic regression analysis revealed that GBS colonization was a factor associated with PTB before 34 and before 37 weeks of gestation (Odds ratio [OR] 15.17; 95% confidence interval [CI] 3.73-61.74), and OR 2.42; 95%CI 1.01-5.91, respectively).

CONCLUSIONS

The present study found that vaginal GBS colonization in the early stage of pregnancy was associated with PTB. Our study indicates that patients at a high risk for PTB can be extracted by a simple method using conventional culture method.

Predominance of Atopobium vaginae at Midtrimester: a Potential Indicator of Preterm Birth Risk in a Nigerian Cohort

Giving birth too soon accounts for half of all newborn deaths worldwide. Clinical symptoms alone are not sufficient to identify women at risk of giving birth too early, as such a pragmatic approach to reducing the incidence of preterm birth entails developing early strategies for intervention before it materializes.

Preterm birth (PTB) is the largest contributor to infant death in sub-Saharan Africa and globally. With a global estimate of 773,600, Nigeria has the third highest rate of PTB worldwide. There have been a number of microbiome profiling studies to identify vaginal microbiomes suggestive of preterm and healthy birth outcome. However, studies on the pregnancy vaginal microbiome in Africa are sparse with none performed in Nigeria. Moreover, few studies have considered the concurrent impact of steroid hormones and the vaginal microbiome on pregnancy outcome. We assessed two key determinants of pregnancy progression to gain a deeper understanding of the interactions between vaginal microbiome composition, steroid hormone concentrations, and pregnancy outcome. Vaginal swabs and blood samples were prospectively collected from healthy midtrimester pregnant women. Vaginal microbiome compositions were assessed by analysis of the V3-V5 region of 16S rRNA genes, and potential functional metabolic traits of identified vaginal microbiomes were imputed by PICRUSt (phylogenetic investigation of communities by reconstruction of unobserved states) analysis, while plasma estradiol (E2) and progesterone (P1) levels were quantified by the competitive enzyme-linked immunosorbent assay (ELISA). PTB vaginal samples were characterized by increased microbial richness, high diversity, and depletion of lactobacilli compared to term delivery samples. Women who delivered preterm were characterized by an Atopobium vaginae-dominated vagitype. High relative abundance of Atopobium vaginae at the midtrimester was highly predictive of PTB (area under the receiving operator characteristics [AUROC] of 0.983). There was a marked overlap in the range of plasma E2 and P1 values between term and PTB groups.

IMPORTANCE Giving birth too soon accounts for half of all newborn deaths worldwide. Clinical symptoms alone are not sufficient to identify women at risk of giving birth too early, as such a pragmatic approach to reducing the incidence of preterm birth entails developing early strategies for intervention before it materializes. In view of the role played by the vaginal microbiome and maternal steroid hormones in determining obstetric outcome, we assessed the vaginal microbiome composition and steroid hormone during pregnancy and examined their relationship in predicting preterm birth risk in Nigerian women. This study highlights a potential early-driver microbial marker for prediction of preterm birth risk and supports the notion that vaginal microbiome composition varies across populations. A knowledge of relevant preterm birth microbial markers specific to populations would enhance the development of personalized therapeutic interventions toward restoring a microbiome that optimizes reproductive health fitness, therefore reducing the incidence of preterm birth.

The Interaction Between Microorganisms, Metabolites, and Immune System in the Female Genital Tract Microenvironment

The female reproductive tract microenvironment includes microorganisms, metabolites, and immune components, and the balance of the interactions among them plays an important role in maintaining female reproductive tract homeostasis and health. When any one of the reproductive tract microorganisms, metabolites, or immunity is out of balance, it will affect the other two, leading to the occurrence and development of diseases and the appearance of corresponding symptoms and signs, such as infertility, miscarriage, premature delivery, and gynecological tumors caused by infectious diseases of the reproductive tract. Nutrients in the female reproductive tract provide symbiotic and pathogenic microorganisms with a source of nutrients for their own reproduction and utilization. At the same time, this interaction with the host forms a variety of metabolites. Changes in metabolites in the host reproductive tract are related not only to the interaction between the host and microbiota under dysbiosis but also to changes in host immunity or the environment, all of which will participate in the pathogenesis of diseases and lead to disease-related phenotypes. Microorganisms and their metabolites can also interact with host immunity, activate host immunity, and change the host immune status and are closely related to persistent genital pathogen infections, aggravation of infectious diseases, severe pregnancy outcomes, and even gynecological cancers. Therefore, studying the interaction between microorganisms, metabolites, and immunity in the reproductive tract cannot only reveal the pathogenic mechanisms that lead to inflammation of the reproductive tract, adverse pregnancy outcomes and tumorigenesis but also provide a basis for further research on the diagnosis and treatment of targets.

The Association Between Vaginal Microbiota Dysbiosis, Bacterial Vaginosis, and Aerobic Vaginitis, and Adverse Pregnancy Outcomes of Women Living in Sub-Saharan Africa: A Systematic Review

Background: Previous studies have described the association between dysbiosis of the vaginal microbiota (VMB) and related dysbiotic conditions, such as bacterial vaginosis (BV) and aerobic vaginitis (AV), and various adverse pregnancy outcomes. There is limited overview of this association from countries in sub-Saharan Africa (SSA), which bear a disproportionally high burden of both vaginal dysbiotic conditions and adverse pregnancy outcomes. This systematic review assesses the evidence on the association between VMB dysbiosis, BV, and AV, and late adverse pregnancy outcomes in women living in SSA.

Methods: The Preferred Reporting Items for Systematic Review and Meta-Analysis Statement (PRISMA) guidelines were followed. Three databases [PubMed, Embase (Ovid), and Cochrane] were used to retrieve observational and intervention studies conducted in SSA that associated VMB dysbiosis, BV, or AV and preterm birth/labor/delivery, preterm rupture of membranes (PROM), low birthweight, small for gestational age, intrauterine growth restriction, intrauterine infection, intrauterine (fetal) death, stillbirth, perinatal death, or perinatal mortality.

Results: Twelve studies out of 693 search records from five SSA countries were included. One study identified a positive association between VMB dysbiosis and low birthweight. Despite considerable differences in study design and outcome reporting, studies reported an association between BV and preterm birth (7/9), low birthweight (2/6), PROM (2/4), intrauterine infections (1/1), and small for gestational age (1/1). None of the retrieved studies found an association between BV and pregnancy loss (5/5) or intrauterine growth retardation (1/1). At least two studies support the association between BV and PROM, low birthweight, and preterm birth in Nigerian pregnant women. No reports were identified investigating the association between AV and late adverse pregnancy outcomes in SSA.

Conclusion: Two of the included studies from SSA support the association between BV and PROM. The remaining studies show discrepancies in supporting an association between BV and preterm birth or low birthweight. None of the studies found an association between BV and pregnancy loss. As for the role of VMB dysbiosis, BV, and AV during pregnancy among SSA women, additional research is needed. These results provide useful evidence for prevention efforts to decrease vaginal dysbiosis and its contribution to adverse pregnancy outcomes in SSA.

Probiotics and the envisaged role in treating human infertility

Background

Considerable attention is being directed nowadays towards using probiotics as an alternative therapy in treating several human diseases including gastrointestinal tract diseases especially colorectal cancers, cardiovascular diseases, hyperlipidemia, and blood pressure cases. However, infertility as affected by the microbiome and the probable role of probiotics in alleviating infertility problems did not receive the deserved attention, especially in IVF patients with male or female factors.

Main body

In this review, we tried to draw the attention of researchers in the medical settings to the importance of the forthcoming role of probiotics use in elucidating the role of the microbiome in infertile patients. The hope is to attain the best performance of both male and female reproductive systems and to shed some light on infertility problems.

Conclusion

More in vivo experiments are still needed to address many aspects of probiotics like proper administration, exact functional strains, required dose, application method, duration of treatment, and combination with antibiotics before considering probiotics as an alternative treatment.

Identification of Potential Biomarkers in the Cervicovaginal Fluid by Metabolic Profiling for Preterm Birth

During pregnancy, dysbiosis in the vaginal microbiota directly affects the metabolic profiles, which might impact preterm birth (PTB). In this study, we performed cervicovaginal fluid (CVF) metabolic profiling using nuclear magnetic resonance (NMR) spectroscopy and identified the metabolic markers for predicting PTB. In this nested case-control study, 43 South Korean pregnant women with PTB (n = 22), and term birth (TB; n = 21) were enrolled with their demographic profiles, and CVF samples were collected by vaginal swabs. The PTB group had two subgroups based on post-CVF sampling birth: PTB less than (PTB < 7 d) and more than 7 days (PTB ≥ 7 d). We observed significant differences in the gestational age at birth (GAB), cervical length (CL), and neonatal birth weight among the groups. The principal component analysis (PCA), and partial least square discriminant analysis (PLS-DA) scatter plot showed the separation between the PTB < 7 d group, and the TB group. Out of 28 identified metabolites, acetone, ethanol, ethylene glycol, formate, glycolate, isopropanol, methanol, and trimethylamine N-oxide (TMAO) were significantly increased in the PTB group compared with the TB group. The ROC curve analysis revealed that the acetone, ethylene glycol, formate, glycolate, isopropanol, methanol, and TMAO had the best predictive values for PTB. Additionally, the correlation analysis of these metabolites showed a strong negative correlation with GAB and CL. These metabolites could be beneficial markers for the clinical application of PTB prediction.

Cervicovaginal fluid cytokines as predictive markers of preterm birth in symptomatic women

Objective

Here, we investigated whether cytokines in the cervicovaginal fluid (CVF) can be predictive markers of preterm birth (PTB).

Methods

A multi-center prospective cohort study was conducted on 59 singleton pregnant women hospitalized for preterm labor (PTL) and/or preterm premature rupture of membranes (pPROM) between 22 weeks and 36 weeks 6 days of gestation from 2014 to 2015. The levels of 13 inflammatory cytokines (macrophage inflammatory protein [MIP]-1α, MIP-1β, tumor necrosis factor [TNF]-α, interleukin [IL]-1β, IL-6, IL-8, IL-17α, granulocyte colony stimulating factor [G-CSF], IL-7, IL-4, IL-5, IL-10, and IL-13) were measured using a multiplex bead-based immunoassay and that of fetal fibronectin (fFN) was measured using enzyme-linked immunosorbent assay (ELISA). Statistical analyses were performed using Student’s t-test, Mann-Whitney U test, Pearson’s correlation, and receiver operating characteristic (ROC) curve analysis in SPSS version 20.0.

Results

Among the 13 cytokines assessed, the levels of 3 cytokines (MIP-1α, IL-6, and IL-7) were negatively correlated with gestational age at delivery (P=0.028, P=0.002, and P=0.018, respectively). Sensitivities of MIP-1α, IL-6, and IL-17α were 70%, 80%, and 75%, respectively, and their specificities were 57%, 65%, and 69%, respectively. The sensitivity and specificity of fFN were 33% and 95%, respectively.

Conclusion

In symptomatic women diagnosed with PTL and/or pPROM, cytokines from cervicovaginal fluid, especially IL-6 and IL-17α, could be better predictive markers of PTB than fFN.

Identification and evaluation of the microbiome in the female and male reproductive tracts

BACKGROUND

The existence of an extensive microbiome in and on the human body has increasingly dominated the scientific literature during the last decade. A shift from culture-dependent to culture-independent identification of microbes has occurred since the emergence of next-generation sequencing (NGS) techniques, whole genome shotgun and metagenomic sequencing. These sequencing analyses have revealed the presence of a rich diversity of microbes in most exposed surfaces of the human body, such as throughout the reproductive tract. The results of microbiota analyses are influenced by the technical specifications of the applied methods of analyses. Therefore, it is difficult to correctly compare and interpret the results of different studies of the same anatomical niche.

OBJECTIVES AND RATIONALE

The aim of this narrative review is to provide an overview of the currently used techniques and the reported microbiota compositions in the different anatomical parts of the female and male reproductive tracts since the introduction of NGS in 2005. This is crucial to understand and determine the interactions and roles of the different microbes necessary for successful reproduction.

SEARCH METHODS

A search in Embase, Medline Ovid, Web of science, Cochrane and Google scholar was conducted. The search was limited to English language and studies published between January 2005 and April 2018. Included articles needed to be original microbiome research related to the reproductive tracts.

OUTCOMES

The review provides an extensive up-to-date overview of current microbiome research in the field of human reproductive medicine. The possibility of drawing general conclusions is limited due to diversity in the execution of analytical steps in microbiome research, such as local protocols, sampling methods, primers used, sequencing techniques and bioinformatic pipelines, making it difficult to compare and interpret results of the available studies. Although some microbiota are associated with reproductive success and a good pregnancy outcome, it is still unknown whether a causal link exists. More research is needed to further explore the possible clinical implications and therapeutic interventions.

WIDER IMPLICATIONS

For the field of reproductive medicine, determination of what is a favourable reproductive tract microbiome will provide insight into the mechanisms of both unsuccessful and successful human reproduction. To increase pregnancy chances with live birth and to reduce reproduction-related health costs, future research could focus on postponing treatment or conception in case of the presence of unfavourable microbiota and on the development of therapeutic interventions, such as microbial therapeutics and lifestyle adaptations.

The Interplay Between Reproductive Tract Microbiota and Immunological System in Human Reproduction

In the last decade, the microbiota, i.e., combined populations of microorganisms living inside and on the surface of the human body, has increasingly attracted attention of researchers in the medical field. Indeed, since the completion of the Human Microbiome Project, insight and interest in the role of microbiota in health and disease, also through study of its combined genomes, the microbiome, has been steadily expanding. One less explored field of microbiome research has been the female reproductive tract. Research mainly from the past decade suggests that microbial communities residing in the reproductive tract represent a large proportion of the female microbial network and appear to be involved in reproductive failure and pregnancy complications. Microbiome research is facing technological and methodological challenges, as detection techniques and analysis methods are far from being standardized. A further hurdle is understanding the complex host-microbiota interaction and the confounding effect of a multitude of constitutional and environmental factors. A key regulator of this interaction is the maternal immune system that, during the peri-conceptional stage and even more so during pregnancy, undergoes considerable modulation. This review aims to summarize the current literature on reproductive tract microbiota describing the composition of microbiota in different anatomical locations (vagina, cervix, endometrium, and placenta). We also discuss putative mechanisms of interaction between such microbial communities and various aspects of the immune system, with a focus on the characteristic immunological changes during normal pregnancy. Furthermore, we discuss how abnormal microbiota composition, “dysbiosis,” is linked to a spectrum of clinical disorders related to the female reproductive system and how the maternal immune system is involved. Finally, based on the data presented in this review, the future perspectives in diagnostic approaches, research directions and therapeutic opportunities are explored.

Defining microbial biomarkers for risk of preterm labor

Preterm birth remains the main contributor to early childhood mortality. The vaginal environment, including microbiota composition, might contribute to the risk of preterm delivery. Alterations in the vaginal microbial community structure might represent a risk factor for preterm birth. Here, we aimed to (a) investigate the association between preterm birth and the vaginal microbial community and (b) identify microbial biomarkers for risk of preterm birth. Microbial DNA was isolated from vaginal swabs in a cohort of 69 women enrolled at hospital admission for their delivery. Microbiota was analyzed by high-throughput 16S rRNA sequencing. While no differences in microbial diversity measures appeared associated with the spontaneous preterm and full-term outcomes, the microbial composition was distinct for these groups. Differential abundance analysis showed Lactobacillus species to be associated with full-term birth whereas an unknown Prevotella species was more abundant in the spontaneous preterm group. Although we studied a very miscegenated population from Brazil, our findings were similar to evidence pointed by other studies in different countries. The role of Lactobacillus species as a protector in the vaginal microbiome is demonstrated to be also a protector of spontaneous preterm outcome whereas the presence of pathogenic species, such as Prevotella spp., is endorsed as a factor of risk for spontaneous preterm delivery.

Female genital tract microbiota affecting the risk of preterm birth: What do we know so far? A review

Spontaneous Preterm birth (SPTB) is a common obstetric complication affecting 12.9 million births worldwide and is the leading cause of neonatal morbidity and mortality. Disruption in the vaginal microbiota has an impact on the maternal immunological profile leading to SPTBs. Scientists have struggled to link maternal infectious agents with the dysregulation of the maternal immune response in cases of SPTBs. Throughout the last decade, important findings regarding the role of microbiota and its genome, the so-called microbiome, have linked alterations within the population of the microorganisms in our bodies with changes in nutrition, immunity, behaviour and diseases. In this review, evidence regarding the female genital tract microbiota and microbiome has been examined to help further our understanding of its role in disrupting the maternal immune system resulting in spontaneous preterm birth.

Vaginal Microbiome Signature Is Associated With Spontaneous Preterm Delivery

Background: Preterm delivery (PTD) represents an important public health and therapeutic challenge. Despite the reported link between the composition of vaginal microbiome and PTD, previous studies were inconsistent in their conclusions and utilized non-uniform designs. We performed an independent case-control study carried out on the Slovenian population, where we re-evaluated the role of the vaginal microbiome in PTD.

Methods: Vaginal microbiomes of pregnant women who delivered preterm were compared to those delivered at term to examine differences in the microbial richness, diversity, and differential abundance of specific taxa. We obtained vaginal swab samples from 155 Caucasian women who were classified as either term (≥38^0/7 weeks, n = 107) or preterm (≤36^6/7 weeks, n = 48) in exclusion of any other medical or obstetric conditions. The vaginal microbiomes of these women were characterized by 16S ribosomal RNA (rRNA) gene sequencing of the V3-V4 region on the MiSeq platform.

Results: Women who experienced PTD had a higher microbial richness (Chao1, P = 0.011) and alpha diversity (Shannon, P = 0.00059) than women with term deliveries. We report that overall vaginal microbial community composition (beta-diversity) was significantly different by delivery gestational age category (P_{WeightedUnifrac} < 0.001). Women who delivered preterm had decreased Lactobacilli spp. abundance as well as increased abundance of Gardnerella and other bacterial vaginosis (BV) and aerobic vaginitis (AV) associated genera including Atopobium, Sneathia, Gemella, Megasphaera, Dorea, Streptococcus, and Escherichia/Shigella.

Conclusions: In the present study, we provide further evidence that vaginal microbiome composition is associated with PTD.

Association between the vaginal microbiome and high-risk human papillomavirus infection in pregnant Chinese women

BACKGROUND

In this study, the association between high-risk human papillomavirus (hrHPV) infection and the vaginal microbiome in pregnant women was evaluated in Chinese cohorts.

METHODS

The vaginal bacterial composition of four groups, 38 hrHPV-infected pregnant women (PHR, n = 38), pregnant women without HPV infection (PN, n = 48), nonpregnant women with hrHPV infection (NPHR, n = 19) and nonpregnant women without HPV infection (NPN, n = 30), was characterized by deep sequencing of barcoded 16S rRNA gene fragments (V3-4) using Illumina MiSeq.

RESULTS

The results revealed that both pregnancy and HPV infection can increase vaginal bacterial microbial richness and diversity, with the bacterial composition being most influenced by pregnancy. Lactobacillus was the most dominant genus among all samples. NPN samples were dominated by CST (community state type) III, mainly composed of Lactobacillus iners. Both pregnancy and hrHPV infection were accompanied by an increased proportion of CST I (dominated by Lactobacillus crispatus), as opposed to CST III. Bifidobacterium, Bacillus, Megasphaera, Sneathia, Prevotella, Gardnerella, Fastidiosipila and Dialister were found to be biomarkers for hrHPV-infected women, though different genera (Bifidobacterium, Megasphaera, Bacillus, Acidovorax, Oceanobacillus and Lactococcus) were associated with hrHPV-infected pregnant women.

CONCLUSIONS

This work uncovered a probable synergistic effect of hrHPV infection and pregnancy on the vaginal microbial composition. HPV infection in pregnant women was associated with a more complex and diverse microbial environment.

Vaginal microbiome profiles of pregnant women in Korea using a 16S metagenomics approach

PROBLEM

The stability and dominance of Lactobacillus spp. in vaginal fluid are important for reproductive health. However, the characterization of the vaginal microbiota of women with preterm labor (PTL) or preterm premature rupture of membranes (P-PROM), and its association with preterm birth (PTB) are poorly understood.

METHOD OF STUDY

We collected vaginal fluid from women at risk of PTB (n = 58) in five university hospitals in Korea. We performed a hierarchical clustering analysis and classification according to the Lactobacillus spp. and Lactobacillus abundance using Illumina MiSeq sequencing of 16S rRNA gene amplicons.

RESULTS

Women at risk for PTB caused by P-PROM had greater bacterial richness and diversity at the time of admission than those with PTL (P < 0.05). However, they were not significantly different between term and preterm samples. In the classification by Lactobacillus spp., the community commonly dominated by Bacteroides and Lactobacillus crispatus was found for the first time in pregnant women in Korea, and all women with this community delivered preterm. Intriguingly, women with an abundance of Weissella in a Bacteroides-dominant community delivered at term. Moreover, in the classification by Lactobacillus proportion, the abundances of Weissella and Rickettsiales were associated with term deliveries, but the abundances of Bacteroides and Escherichia-Shigella were associated with PTBs (P < 0.05).

CONCLUSION

This result suggests that Lactobacillus abundance-based classification of vaginal fluid may reveal the microbiome associated with PTB. Further studies are needed to investigate the mechanism underlying the link between the microbiome and PTB.

Immune tolerance attenuates gut dysbiosis, dysregulated uterine gene expression and high-fat diet potentiated preterm birth in mice

BACKGROUND

Preterm delivery accounts for 85% of perinatal morbidity and mortality. Although the consumption of a high-fat diet leads to exaggerated proinflammatory responses and, in pregnant women, increased rates of spontaneous preterm birth, the underlying mechanisms remain unclear.

OBJECTIVE

We sought to elucidate the mechanisms by which maternal consumption of a high-fat diet leads to a dysregulated immune response and, subsequently, spontaneous preterm birth.

STUDY DESIGN

We performed 16S ribosomal RNA sequencing of DNA extracted and amplified from stool samples and compared the gut microbiomes of lipopolysaccharide-induced pregnant mice that were maintained on a high-fat diet compared to a normal control diet. Next, we sequenced the uterine transcriptomes of the mice. To test the effect of dampening of the immune response on the microbiome, transcriptome, and risk of spontaneous preterm birth, we induced immune tolerance with repetitive subclinical doses (0.2 mg/kg/week for 8 weeks) of endotoxin and performed 16S ribosomal RNA and uterine transcriptome sequencing on these immunotolerized mice.

RESULTS

High-fat diet potentiates lipopolysaccharide-induced preterm birth by affecting the maternal gut microbiome and uterine transcriptome and reduces antioxidant capacity in a murine model. High-fat diet consumption also increases the colonization of the gut by 5 immunogenic bacteria and decreases colonization by Lachnospiraceae_NK4A136_group. Uteri from high-fat diet mice had increased expression of genes that stimulate the inflammatory-oxidative stress axis, autophagy/apoptosis, and smooth muscle contraction. Repetitive endotoxin priming protects high-fat diet dams from spontaneous preterm birth, increases colonization of the gut by Lachnospiraceae_NK4A136_group, decreases levels of immunogenic bacteria in the gut microbiome, and reduces the number of dysregulated genes after high-fat diet consumption from 994 to 74.

CONCLUSION

High-fat diet-potentiated spontaneous preterm birth is mediated by increased inflammation, oxidative stress, and gut dysbiosis. The induction of immune tolerance via endotoxin priming reverses these effects and protects high-fat diet dams from spontaneous preterm birth. Based on this work, the role of immunomodulation as a novel therapeutic approach to prevent preterm birth among women who consume high-fat diets should be explored.

The vaginal microbiome and preterm birth

The incidence of preterm birth exceeds 10% worldwide. There are significant disparities in the frequency of preterm birth among populations within countries, and women of African ancestry disproportionately bear the burden of risk in the United States. In the present study, we report a community resource that includes ‘omics’ data from approximately 12,000 samples as part of the integrative Human Microbiome Project. Longitudinal analyses of 16S ribosomal RNA, metagenomic, metatranscriptomic and cytokine profiles from 45 preterm and 90 term birth controls identified harbingers of preterm birth in this cohort of women predominantly of African ancestry. Women who delivered preterm exhibited significantly lower vaginal levels of Lactobacillus crispatus and higher levels of BVAB1, Sneathia amnii, TM7-H1, a group of Prevotella species and nine additional taxa. The first representative genomes of BVAB1 and TM7-H1 are described. Preterm-birth-associated taxa were correlated with proinflammatory cytokines in vaginal fluid. These findings highlight new opportunities for assessment of the risk of preterm birth.

As part of the second phase of Human Microbiome Project, the Multi-Omic Microbiome Study: Pregnancy Initiative presents a community resource to help better understand how microbiome and host profiles change throughout pregnancy as well as to identify new opportunities for assessment of the risk of preterm birth.