Around 1–5% of all couples experience recurrent pregnancy loss (RPL). Established risk factors include anatomical, genetic, endocrine, and hemostatic alterations. With around 50% of idiopathic cases, immunological risk factors are getting into the scientific focus, however international guidelines hardly take them into account. Within this review, the current state of immunological risk factors in RPL in international guidelines of the European Society of Reproduction and Embryology (ESHRE), American Society of Reproductive Medicine (ASRM), German/Austrian/Swiss Society of Obstetrics and Gynecology (DGGG/OEGGG/SGGG) and the Royal College of Obstetricians and Gynecologists (RCOG) are evaluated. Special attention was drawn to recommendations in the guidelines regarding diagnostic factors such as autoantibodies, natural killer cells, regulatory T cells, dendritic cells, plasma cells, and human leukocyte antigen system (HLA)-sharing as well as treatment options such as corticosteroids, intralipids, intravenous immunoglobulins, aspirin and heparin in RPL. Finally, the current state of the art focusing on both diagnostic and therapeutic options was summarized.

Vaginal dysbiosis covers imbalances in the vaginal microbiota, defined by altered composition of bacteria, viruses, and fungi and is associated with euploid pregnancy losses, premature birth, infertility, or bacterial vaginosis. A large proportion of women who have vaginal dysbiosis do not experience any symptoms. Antibiotics are the traditional treatment, recently combined with local probiotics in some cases. Vaginal Microbiota Transplantation (VMT) with eubiotic vaginal bacterial microbiota after antibiotic eradication of pathogens has successfully been performed in a case study with five patients, but no VMT has been performed without the use of antibiotics. This is a proof of concept case study. The patient was found to have vaginal dysbiosis at the RPL clinic at Copenhagen University Hospital Hvidovre, Denmark on the 23rd of June 2021. She was offered and accepted to receive experimental treatment in the form of a VMT as a compassionate use case. VMT is the transfer of cervicovaginal secretions (CVS) from a healthy donor with a Lactobacillus-dominant vaginal microbiome to a recipient with a dysbiotic vaginal microbiome. CVS is a mixture of e.g., mucus, bacteria, metabolites present in the vaginal canal. Potential donors were thoroughly screened for the absence of STIs, and the most suitable donor sample for the specific patient in this study was determined via an in vitro microbiome competition assay. A 30-year-old patient with one livebirth and a complicated pregnancy history of two stillbirths and 1 s trimester pregnancy loss in gestational weeks 27 (2019), 17 (2020) and 23 (2020) respectively with complaints of vaginal irritation and discharge that had aggravated in all her pregnancies. Her vaginal microbiome composition showed a 90% dominance of Gardnerella spp. After one VMT there was a complete shift in microbiome composition to 81.2% L. crispatus and 9% L. jensenii with a concurrent resolvement of vaginal symptoms. Single nucleotide polymorphism-analysis confirmed her microbiome to be of donor origin and it remain stable now 1.5 years after the VMT. Five months after the VMT she became pregnant and has successfully delivered a healthy baby at term. Here we report a successful VMT with confirmed donor strain engraftment followed by a successful pregnancy and delivery after a series of late pregnancy losses/stillbirths. Findings suggest that VMT is a potential treatment for severe vaginal dysbiosis. Further, larger studies are required. The study was partially funded (i.e., analysis costs) by Freya Biosciences Aps, Fruebjergvej, 2100 Copenhagen, Denmark.

Introduction Supporting and counselling couples with fertility issues prior to starting ART is a multidisciplinary diagnostic and therapeutic challenge. The first German/Austrian/Swiss interdisciplinary S2k guideline on “Diagnosis and Therapy Before Assisted Reproductive Treatments (ART)” was published in February 2019. This guideline was developed in the context of the guidelines program of the German Society of Gynecology and Obstetrics (DGGG) in cooperation with the Swiss Society of Gynecology and Obstetrics (SGGG) and the Austrian Society of Gynecology and Obstetrics (OEGGG). Aims One third of the causes of involuntary childlessness are still unclear, even if the woman or man have numerous possible risk factors. Because the topic is still very much taboo, couples may be socially isolated and often only present quite late to a fertility center. At present, there is no standard treatment concept, as currently no standard multidisciplinary procedures exist for the diagnostic workup and treatment of infertility. The aim of this guideline is to provide physicians with evidence-based recommendations for counselling, diagnostic workup and treatment. Methods This S2k guideline was developed on behalf of the Guidelines Commission of the DGGG by representative members from different professional medical organizations and societies using a structured consensus process. Recommendations The first part of this guideline focuses on the basic assessment of affected women, including standard anatomical and endocrinological diagnostic procedures and examinations into any potential infections. Other areas addressed in this guideline are the immunological workup with an evaluation of the patientʼs vaccination status, an evaluation of psychological factors, and the collection of data relating to other relevant factors affecting infertility. The second part will focus on explanations of diagnostic procedures compiled in collaboration with specialists from other medical specialties such as andrologists, human geneticists and oncologists.

Background: RPL and RIF are challenges in reproductive medicine. The immune system plays a pivotal role in endometrial receptivity, successful implantation, and pregnancy complications. Immunological changes have been associated with RPL and RIF. Understanding immune dysregulation especially in NK and T cell subtypes may lead to better diagnostic concepts and treatments. From July 2019 to August 2020 patients with RPL and RIF underwent a standardized diagnostic procedure including endometrial biopsies. Immune cell analysis was performed using flow cytometry. Patients were contacted in March 2023 and interviewed concerning their pregnancy outcomes following diagnostics. Results: Out of 68 patients undergoing endometrial biopsies, 49 patients were finally included. Live birth rates were high with 72% in RPL and 86% in RIF. Immune cell analysis revealed that patients with RPL had more cytotoxic CD56^dimCD16^high cells, while RIF patients had more CD56⁺ uNK cells. RPL patients with pregnancy complications showed increased NKT cell percentages. Conclusion: Our findings suggest specific immune changes in RPL and RIF patients, offering potential therapeutic targets. Tailored immunotherapy based on endometrial immunophenotyping might be an option, but further research is needed.

Intracytoplasmic sperm injection (ICSI) and conventional in vitro fertilization (c-IVF) are widely used fertilization techniques in assisted reproduction, but their relative effectiveness in patients without severe male factor infertility remains debated. While ICSI’s role in couples with severe male factor infertility is well established, its routine use in cases with normal or nonseverely decreased sperm quality is not evidence-based. Here we conducted the INVICSI study, an open-label, multicenter randomized controlled trial, to compare cumulative live birth rates (CLBR) as the primary outcome between ICSI and c-IVF in patients without severe male factor infertility. Between November 2019 and December 2022, 824 women undergoing their first IVF cycle were randomized to ICSI (n = 414) or c-IVF (n = 410) across six public fertility clinics in Denmark. The CLBR was 43.2% (179/414) in the ICSI group and 47.3% (193/408) in the c-IVF group, yielding a risk ratio of 0.91 (95% confidence interval, 0.79–1.06). These findings demonstrate that ICSI does not improve CLBR compared to c-IVF and support c-IVF as the preferred first-line treatment for patients with normal or nonseverely decreased sperm quality. ICSI should be reserved for severe male factor infertility. ClinicalTrials.gov registration: NCT04128904.

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.