The microbiome in recurrent pregnancy loss - A scoping review.

Recurrent pregnancy loss (RPL) is a troubling condition that affects couples worldwide. Despite extensive research efforts, many RPL cases remain unexplained, highlighting the need for novel approaches to unravel its underlying mechanisms. Recent advances in microbiome research have shed light on the potential role of the microbiome in reproductive health and outcomes. Based on a systematic literature research, this review aims to comprehensively explore the current understanding of the microbiome's involvement in RPL, focusing on the vaginal, endometrial, and gut microbiomes. Evidence from the available studies is examined to explain the relationship between the microbiome and RPL. Furthermore, we discuss the diagnostic potential of the microbiome, therapeutic interventions, and future directions in microbiome research for RPL. Understanding the complex interactions between the microbiome and reproductive health holds promise for developing targeted interventions to help patients today diagnosed as unexplained.

Interaction Between Chronic Endometritis Caused Endometrial Microbiota Disorder and Endometrial Immune Environment Change in Recurrent Implantation Failure.

Objective: To investigate the Interaction between chronic endometritis (CE) caused endometrial microbiota disorder and endometrial immune environment change in recurrent implantation failure (RIF). Method: Transcriptome sequencing analysis of the endometrial of 112 patients was preform by using High-Throughput Sequencing. The endometrial microbiota of 43 patients was analyzed by using 16s rRNA sequencing technology. Result: In host endometrium, CD4 T cell and macrophage exhibited significant differences abundance between CE and non-CE patients. The enrichment analysis indicated differentially expressed genes mainly enriched in immune-related functional terms. Phyllobacterium and Sphingomonas were significantly high infiltration in CE patients, and active in pathways related to carbohydrate metabolism and/or fat metabolism. The increased synthesis of lipopolysaccharide, an important immunomodulator, was the result of microbial disorders in the endometrium. Conclusion: The composition of endometrial microorganisms in CE and non-CE patients were significantly different. Phyllobacterium and Sphingomonas mainly regulated immune cells by interfering with the process of carbohydrate metabolism and/or fat metabolism in the endometrium. CE endometrial microorganisms might regulate Th17 response and the ratio of Th1 to Th17 through lipopolysaccharide (LPS).

Interactions between gut microbiota and metabolites modulate cytokine network imbalances in women with unexplained miscarriage.

A dysregulation of cytokine networks has been suggested to be involved in the pathogenesis of unexplained pregnancy loss. Gut microbiota affects host immune response and induces an imbalance in cytokine levels. However, how gut microbial dysbiosis disturbs cellular immune function in miscarriage remains inconclusive. Here we report that IL-2, IL-17A, IL-17F, TNF-α, and IFN-γ are significantly increased in serum of miscarriage patients. Fecal microbiome analyses indicate that microbial diversity and the relative abundances of Prevotella_1, Prevotellaceae_UCG_003 and Selenomonas_1 are significantly reduced in the cases. Correlation analyses indicate that some microbe-associated metabolites are positively associated with changes in levels of Th1/Th17 cytokines in the miscarriage group. Moreover, we identify that imidazolepropionic acid and 1,4-methylimidazoleacetic acid are associated with subsequent recurrent miscarriage. Our study highlights the network among gut microbiota, fecal metabolites and Th1/Th17-mediated immune response in miscarriage patients and explores the potential predictive values of two fecal metabolites for recurrent miscarriages.

Molecular Evaluation of Chlamydia trachomatis Infection and Its Association with Tumor Necrosis Factor-α Polymorphism in Recurrent Spontaneous Abortions.

Background: The rate of infections in the intensive care units (ICUs) is rising, mainly because of the increasing use of invasive procedures. Several bacterial infections and host genetic backgrounds, including TNFα SNP polymorphisms, play important roles in recurrent spontaneous abortions (RSA). So, this study aimed to evaluate C. trachomatis infection and its relation with TNFα -308 and -238 polymorphism for early detection and treatment of RSA. Methods: The blood samples were taken from 63 Iranian women with a history of RSA and 59 ethnically matched healthy controls with at least two successful pregnancies and no history of abortion. Then, DNA was extracted from all samples and detection of C. trachomatis and TNFα -308 and -238 polymorphism was determined by multiplex amplification-refractory mutation system (ARMS)-PCR. Finally, the statistical analysis to detection C. trachomatis and host genetic roles in RSA were analyzed by Epi Info TM software by X2 test. Results: C. trachomatis was detected in 22 and 3% of the RSA and the control group, respectively. Moreover, in comparison with healthy controls, C. trachomatis infection was closely correlated with TNFα -308 genotypes, whereas no significant association was observed between TNFα -238G/A and RSA. In addition, statistical analysis of TNFα -308 genotypes showed that the frequency of genotype AA was higher in patients with C. trachomatis infections than healthy individuals and the difference was statistically significant. Conclusions: This study demonstrated that molecular analysis of TNF -308 genotypes is important in early detection and treatment of RSA with C. trachomatis infection.

Cytokine-induced expression of nitric oxide synthases in Chlamydia trachomatis-infected spontaneous aborters.

Purpose: The aim of study was to evaluate expression of inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS), interferon-gamma (IFN-γ), and tumor necrosis factor-alpha (TNF-α) in Chlamydia trachomatis (CT)-infected spontaneous aborters (SA). Materials and methods: Endometrial curettage tissue was collected from 140 SA (sporadic SA- 70; recurrent SA- 70) (Group I) and 140 age-matched controls (Group II) from Department of Obstetrics and Gynecology, Safdarjung Hospital, New Delhi, India. Polymerase chain reaction was performed for diagnosis of CT. The expression of iNOS/ eNOS/ IFN-γ/ TNF-α was assessed by real-time polymerase chain reaction (PCR). Results: 15.7% SA were CT-positive (Group I); none in controls. Sporadic spontaneous aborters (SSA) (n = 8/70), recurrent spontaneous aborters (RSA) (n = 14/70) diagnosed as CT-positive (Group-I). Significant upregulation of iNOS/ eNOS was found in CT-positive SSA/RSA compared with CT-negative SSA/RSA and healthy controls. TNF-α and IFN-γ were expressed in CT-positive SSA/RSA compared with negative SSA/controls. iNOS showed a significant strong positive correlation with TNF-α and IFN-γ in CT-infected SA. eNOS showed a significant positive correlation with TNF-α and no correlation with IFN-γ in CT-infected SA. TNF-α was positively correlated with IFN-γ. Conclusions: Significantly high expression of iNOS/ eNOS and proinflammatory cytokines affected pregnancy in CT-infected RSA, thereby implying that there occurs cytokine-induced expression of nitric oxide synthase (NOS).

Systematic Comparison of Bacterial Colonization of Endometrial Tissue and Fluid Samples in Recurrent Miscarriage Patients: Implications for Future Endometrial Microbiome Studies.

BACKGROUND: A recent study has reported that the microbiota in endometrial fluid of patients receiving in vitro fertilization and embryo transfer (IVF-ET) may predict implantation and pregnancy rates. However, studies are lacking that simultaneously compare the microbiota between endometrial fluid and tissue samples. Whether the microbiota composition in endometrial fluid reflects that in the endometrial tissue remains unclear. METHODS: We systematically profiled the microbiota in endometrial fluid and tissue samples of IVF-ET patients using massively parallel sequencing. The bacterial 16S ribosomal RNA gene (V4 region) was PCR-amplified. Sequencing reads with >98% nucleotide identity were clustered as a bacterial taxon. To account for the different number of reads per sample, we normalized the read counts of each taxon before comparing its relative abundances across samples. RESULTS: Thirteen taxa, including Verrucomicrobiaceae, Brevundimonas, Achromobacter, Exiguobacterium, and Flavobacterium, were consistently detected only in endometrial tissue samples but not fluid samples. Eight taxa were detected in fluid but not tissue. Twenty-two taxa were differentially abundant between fluid and tissue samples (adjusted P values, 4.1 × 10-25 to 0.025). The numbers of taxa identified per 1000 sequencing reads, diversity, and evenness in fluid samples were smaller than those in tissue samples. CONCLUSIONS: Our data suggest that the microbiota composition in endometrial fluid does not fully reflect that in endometrial tissue. Sampling from both endometrial fluid and biopsy allows a more comprehensive view of microbial colonization. Further efforts are needed to identify the preanalytical effects, including sampling sites, methods, and sequencing depth, on profiling endometrial microbiota.

Expression of prostaglandin receptors in Chlamydia trachomatis-infected recurrent spontaneous aborters.

A study was undertaken to quantify the expression of prostaglandin (PG) receptors and find the effect of gestational age on expression of PG receptor genes in Chlamydia trachomatis-infected recurrent spontaneous aborters (RSA). Endometrial curettage tissue (ECT) was collected from 130 RSA (Group I) and 100 age-matched controls (Group II) at the Department of Obstetrics and Gynecology, Safdarjung Hospital, New Delhi (India). PCR was performed for diagnosis of C. trachomatis cryptic plasmid; mRNA expression of PG receptor genes was assessed by real-time PCR (q-PCR), while serum progesterone/estrogen levels were determined by respective commercial kits. Data were evaluated statistically. A total of 15.4 % RSA (GroupI) were diagnosed as C. trachomatis-positive (200 bp), whereas controls were uninfected. q-PCR showed significant upregulation (P<0.0001) of PGE2 (EP-1, EP-2, EP-3, EP-4), PGF2α (FP) and PGI2 (IP) receptors in Group I versus Group II. The expression of PG receptors increased significantly with advanced gestational age (P<0.002); however, only contractile receptors, EP-1, EP-3 and FP, were positively correlated with gestational age in Group-I. In infected RSA, mean serum progesterone level was significantly low (P<0.0001) while serum oestrogen was high (P<0.0001). Overall, the data suggest that increased expression of PG receptors, particularly contractile gene receptors (EP-1, EP-3, FP), with advanced gestational age and altered steroid levels could be a possible risk factor for abortion in Chlamydia-infected RSA.

Can Porphyromonas gingivalis be a novel aetiology for recurrent miscarriage?

OBJECTIVE: To study the association between Porphyromonas gingivalis (P. gingivalis) infection and recurrent miscarriage. METHODS: This case control study included women with early pregnancy failure admitted for surgical evacuation of retained products of conception. Cases (group 1) included 50 women with unexplained recurrent early miscarriage whereas the control group (group 2) consisted of 50 women with no such history. The evacuated products of conception, subgingival plaques, cervicovaginal secretions and saliva of all participants were examined to detect P. gingivalis deoxyribonucleic acid (DNA) using a polymerase chain reaction. RESULTS: The prevalence of P. gingivalis DNA in the chorionic villous tissue samples of group 1 was significantly higher than in group 2 (8 [16%] vs. 1 [2%], respectively; p = 0.036, odds ratio [OR]: 9.3, 95% confidence interval [CI]: 1.1-76.9). The prevalence of P. gingivalis DNA was significantly higher in cervicovaginal secretions of group 1 than in group 2 (9 [18%] vs. 1 [2%], respectively; p = 0.02, OR: 10.8, 95% CI: 1.3-88.5). On the contrary, P. gingivalis DNA could not be detected in subgingival plaques and saliva samples of either group. CONCLUSION: The current study found an association between P. gingivalis infection of the female genital tract and the occurrence of recurrent miscarriage.

Qual deve ser o rastreamento de doenças infecciosas em casos de perda gestacional recorrente?: [revisão] / What should be the screening of infectious diseases in cases of recurrent pregnancy loss?: [review]

A perda gravídica de repetição ocorre em cerca de 1 a 2% das gestações, e em cerca de em 2% das vezes tem quadros infecciosos como agentes etiológicos. A necessidade de rastreio de causa infecciosa tem sido muito discutida na literatura. Com objetivo de avaliar o que se conhece sobre esta necessidade, foi realizada uma revisão sistemática de trabalhos em inglês, português e espanhol em bases de dados do Pubmed, Highwire, Lilacs e biblioteca Cochrane. Observou-se que, de todos os agentes, o mais estudado foi a Chlamydia trachomatis, em especial seu efeito imunológico tardio. Outros agentes têm sido associados ao aborto habitual, no entanto, as infecções bacterianas, virais e parasitárias podem interferir na evolução da gestação, mas não parece ser uma causa significante de aborto de repetição. O valor do rastreio parece ser limitado na investigação de perda gravídica de repetição fora de um episódio infeccioso agudo. No entanto, mais estudos se fazem necessários, em especial para avaliar efeitos tardios, como das infecções por Chlamydia trachomatis.

The recurrent pregnancy loss occurs in about 1-2% of pregnancies, and in about 2% the etiology would be infectious. The need for tracking infectious causes has been much discussed in the literature. In order to evaluate what is known about this need, we conducted a systematic review of papers in English, Portuguese and Spanish on this subject available in the databases of Pubmed, Highwire, Lilacs and Cochrane Library. Chlamydia trachomatis was mostly studied, especially with regard to its late immunological effect. Other agents have been associated with habitual abortion; however, bacterial infections, viral and parasitic diseases can interfere with the course of gestation, but does not seem to be a significant cause of recurrent abortion. The value of screening seems to be limited for the investigation of recurrent pregnancy loss if acute infection does not occur. However, further studies are needed, especially to evaluate late effects such as infections by Chlamydia trachomatis.

The influence of Chlamydia trachomatis infection on spontaneous abortions.

PURPOSE: The aim of the study was to evaluate the frequency of Chlamydia trachomatis (C.t.) infection among women who experienced a miscarriage. MATERIALS AND METHODS: Patients referred to the Centre for STD Research and Diagnostics in Bialystok from the Department of Perinatology and from gynaecological outpatient clinics, after spontaneous abortion were enrolled in the study. C.t. infection diagnostics were performed among 76 women with 1 miscarriage and 44 patients with > or =2 miscarriages in anamnesis. Forty-six patients in the 2nd and the 3rd trimester of normal pregnancy served as a comparative group. Endocervical swabs as well as blood serum were obtained. To detect chlamydial DNA, direct PCR method was performed (Roche, Molecular Systems, N.J., USA). To detect IgA and IgG specific anti-chlamydial antibodies we used immunoenzymatic assay (medac, Hamburg, Germany). RESULTS: In patients with 1 miscarriage (gr.1), C.t. infection by means of PCR was detected in 11.8% of women (p=0.029), in patients with > or =2 miscarriages (gr.2) in 9.1% (p=0.198) and in the comparative group (gr.0) in 2.2%. Specific anti-chlamydial antibodies IgA class were detected in: 7.9 (p=0.082) in group 1, 4.5% (p=0.236) in group 2 and in 0% in group 0, and IgG class in 21.1% (p=0.024), 36.4% (p=0.000) and in 4.4%, respectively. CONCLUSIONS: 1. C.t. infection is an important causative agent of miscarriages in women. 2. C.t. infection diagnostic procedures should be considered in screening tests during pregnancy.

Espectro clínico de las infecciones por chlamydia trachomatis en mujeres / Clinical spectrum of chlamydia trachomatis infection in women

Hoy en día es incierto el rol que tiene C. trachomatis como causa de efectos adversos durante el embarazo. Pero si está claramente establecido que es causa de EIP en mujer, uretritis y epididimitis en el hombre y conjuntivitis y neumonitis en los niños. La EIP aguda por C. trachomatis tiene un impacto enorme en la reproducción de la mujer: es causa de embarazo tubario e infertilidad por obstrucción tubaria. Por sus consecuencias y porque habitualmente la salpingitis por C. trachomatis es asintomática, es necesario desarrollar estrategias precisas para su control. Se recomienda la pesquisa regular de esta bacteria en la mujer menor de 35 años con factores de riesgo. Es necesario mantener registro de estas infecciones y tratar a la pareja y los contactos. De este modo se pueden prevenir las complicaciones más importantes secundarias a esta infección

Absence of cytomegalovirus in gestational tissue in recurrent spontaneous abortion.

There have been conflicting reports regarding the association of cytomegalovirus (CMV) and recurrent spontaneous abortions. It is difficult to assess the role of CMV in the endometrium by histology alone, since the characteristic cytomegalic virocytes are often scarce or absent in this site. Our purpose was to use the polymerase chain reaction (PCR) to detect cytomegalovirus in gestational tissue of women with recurrent spontaneous abortions. DNA was extracted from 25 samples of paraffin-embedded, formalin-fixed gestational tissue from 21 women with at least three unexplained spontaneous abortions (mean, 3.4). DNA from an unstained paraffin section of each specimen was amplified using nested, multiplex PCR specific for the late antigen and the major immediate early genes of CMV. The assay used has a demonstrated level of sensitivity on the order of 10(-2) virocytes per square centimeter of 4-microM paraffin section. Intact DNA was successfully isolated from 21 specimens in 18 patients. Histologic features of CMV infection were completely absent from these cases, and none of these specimens contained evidence of cytomegalovirus DNA. These findings suggest that CMV infection of gestational tissue is not a common direct cause of recurrent spontaneous abortions.

Virus-host studies in human seminal and mouse testicular cells.

Virological studies were performed for male infertility and repeated abortions. It was found that in about 40% of infertile males infectious adeno- or herpes simplex virus is present in the semen, while the same viruses are present in 60% of the cells in a latent form. In the aborted fetuses the same viruses could be observed as in the father's cells. Due to semen added to tissue cultures the latent presence also of other viruses could be supposed. The affinity of adeno- and herpes viruses to urogenital organs was confirmed by animal experiments, where a new method was applied for in vivo infection. The close correlation between viruses and urogenital cells was similarly confirmed by infecting in vitro human seminal and testicular cells with adeno- and herpes simplex viruses absorbed by the cells, entering them, moreover replicating in the form of their components. Based on the results, it was assumed that chronic local urogenital infections, due to various viruses, may play a role in male infertility and in a part of repeated abortions by damaging their cells. Applying a Zovirax therapy, the seminal cells were stopped to be viral carriers and normal function was restored.

Chlamydia trachomatis infection in "sine causa" recurrent abortion.

One hundred and one women suffering from "sine causa" recurrent abortion were screened for Chlamydia trachomatis (C.T.) infection by using direct examination, cultural and serological procedures. In this series, C.T. infection did not appear to be related to increased risk of recurrent abortion. The culture-positive and serology-positive rates (14.85% and 34.65%, respectively) did not differ from other unselected populations. Neither time from last abortion nor type of abortion were significantly related to C.T. infection. Nonetheless, the women who underwent examination within one year from last abortion and had a culture-positive partner as well, were more likely to present with a C.T.-positive culture.

A possible role of Chlamydia trachomatis in unexplained infertility and sterility.

To estimate the presence of latent Chlamydia Trachomatis (C.T.) infections, we have carried out a study on a selected group of couples affected by unexplained sterility and infertility. We examined 193 women and, as control group 210 healthy fertile women. For both groups the main risk factors that could explain the infection epidemiology have been analyzed. The parameters considered are age of first intercourse, number of partners, social-economic conditions and number of voluntary abortions. Amongst all the causal agents of sexually transmitted diseases (STD), C.T. was most common, with an incidence of about 12 per cent in the study group versus the 5.7 per cent of the control group (chi 2 = 4.12).

PIP: The incidence of Chlamydia infection and factors associated with it in 193 women consulting for infertility was analyzed in comparison with 210 matched controls. All study subjects received a clinical exam, history interview, Pap test, vaginal bacteriology, colposcopy, cervical virology for Chlamydia and enzyme-linked assay for Chlamydia, herpes, rubella and toxoplasma antibodies. Results were tabulated as percent distributions for Chlamydia-positive and -negative in index cases and controls, broken down by the descriptive factors, age at 1st intercourse, number of partners, socio economic class and numbers of induced abortions. 43.5% of the index cases had primary infertility, 21.7% had secondary infertility and 34.8% were sterile. 11.9% of the study group were positive for Chlamydia infection, compared to 5.7% of controls. The only significant difference in factors related to STD infection were: earlier age at 1st intercourse among controls; higher percentage with 3 sexual partners, higher socioeconomic class and more induced abortions in the study group of infertile women; but no difference in chlamydia infection rates with abortion history. This study is unusual in finding higher socioeconomic class in the infertile women than in controls.

Uterine T-mycoplasma colonization in reproductive failure.

In 46 patients with a history of habitual abortion and in 18 women with primary unexplained infertility, samples from cervical mucus and endometrial tissue have been examined for presence of T-mycoplasma, and the results compared to those obtained among 45 control subjects. Colonization of T-mycoplasma in the cervix was found to be common in all patient groups (49 to 83 per cent), whereas colonization in the endometrium was found to be significantly more frequent among the habitual abortion patients (28 per cent) and the infertility patients (50 per cent) than among the control subjects (7 per cent). In all patients having T-mycoplasma-positive endometria the organism was also isolated from the cervix, thus indicating an ascending route for the colonization of the uterine cavity. Bacteria belonging to the normal vaginal flora were frequently co-isolated from the endometrial samples along with T-mycoplasma. The women with T-mycoplasma-positive endometria showed a high incidence of postabortion fever. Treatment with doxycycline eradicated T-mycoplasma from the cervix and the endometrium and apparently led to an improvement with respect to the outcome of the posttreatment pregnancies.

PIP: In 46 patients with a history of habitual abortion and in 18 women with primary unexplained infertility, cervical mucus and endometrial tissue samples were examined for presence of T-mycoplasma, and the results were compared to those obtained amoung 45 control subjects. Colonization of T-mycoplasma in the cervix was found to be common in all patient groups (49-83%), whereas colonization in the endometrium was found to be significantly more frequent among habitual abortion patients (28%) and the infertility patients (50%) than amoung control subjects (7%). In all patients having T-mycoplasma-positive endometria, the organism was also isolated from the cervix, thus indicating an ascending route for the colonization of the uterine cavity. Bacteria belonging to the normal vaginal flora were frequently co-isolated from the endometrial samples along with T-mycoplasma. The women with T-mycoplasma-positive endometria showed a high incidence of postabortion fever. Treatment with doxycycline eradicated T-mycoplasma from the cervix and endometrium and apparently led to an improvement with respect to the outcome of posttreatment pregnancies.