Management of recurrent implantation failure: British Fertility Society policy and practice guideline

Effect of Preimplantation Genetic Testing for Aneuploidy on Live Birth Rate in Young Women With Recurrent Implantation Failure: A Secondary Analysis of a Multicentre Randomised Trial

OBJECTIVE

To investigate the benefit of preimplantation genetic testing for aneuploidy (PGT-A) in recurrent implantation failure (RIF).

DESIGN

Secondary analysis of a multicentre, randomised, double-blind, placebo-controlled clinical trial.

SETTING

Eight academic fertility centres in China, 2018-2020.

POPULATION

Overall, 485 infertile women aged < 38 years were evaluated. They had a history of two or more unsuccessful embryo transfer cycles with at least three good-quality embryos that had been transferred cumulatively and underwent a single blastocyst transfer with or without PGT-A. Those with thin endometrium or recurrent pregnancy loss were excluded.

METHODS

Patients were categorised into PGT-A and non-PGT-A groups. All pregnancies were followed to delivery. Pregnancy and neonatal outcomes were obtained from obstetric and neonatal medical records. Propensity score matching (PSM) and multivariate logistic regression models were applied to adjust for potential confounding factors.

MAIN OUTCOME MEASURES

LBR per embryo transfer.

RESULT(S)

There was no significant difference in LBR between the PGT-A and non-PGT-A groups both before (39.1% vs. 41.5%, p = 0.760) and after (39.1% vs. 40.6%, p = 0.862) PSM. Unadjusted and adjusted logistic regression models revealed no beneficial effect of PGT-A on LBR per embryo transfer (crude odds ratio: 0.91, 95% confidence interval: 0.49-1.69; adjusted odds ratio: 1.04, 95% confidence interval: 0.53-2.03). The incidence of maternal and neonatal complications was not significantly different between the groups.

CONCLUSIONS

Patients with RIF aged < 38 years do not benefit from PGT-A. Thus, factors other than genetic abnormalities may contribute to this clinical conundrum.

Intrauterine infusion of autologous platelet rich plasma can be an efficient treatment for patients with unexplained recurrent implantation failure

The studies posits that there is not sufficient evidence to support the use of intrauterine platelet-rich plasma (PRP) infusion in patients with recurrent implantation failure (RIF). This study aims to investigate the effects of infusion of PRP on patients with unexplained-RIF in fresh and frozen embryo transfer (ET) cycles. A total of 80 participants were included in this study. The participants were randomly assigned to one of two groups with and without PRP infusion. Each of the PRP and control groups were also divided into fresh and frozen ET subgroups. ET outcomes were compared between groups. Clinical pregnancy rate was significantly higher in Frozen ET in PRP group than other subgroups (p < 0.0001). Miscarriage rate were significantly lower in PRP group than control group. Pregnancy complications and preterm labor were significantly higher in PRP group than control group (p < 0.0001). Live birth and healthy baby rate were significantly higher in PRP group than control group (p < 0.0001). The intrauterine infusion of 0.8-1 ml of PRP 48 h before blastocyst ET at fresh and frozen cycles can be an efficient treatment option for u-RIF patients. Also, results indicated that the clinical pregnancy rate was equal to the live birth rate at fresh ET cycles, whereas the live birth rate was lower than the clinical pregnancy rate at frozen ET cycles. Therefore, considering the superiority of fresh cycles over freeze cycles, the infusion of PRP into the uterus of patients with RIF is recommended to be done at fresh ET cycles.Trial registration: NCT, NCT03996837. Registered 25/06/2019. Retrospectively registered, http://www.clinicaltrial.gov/ NCT03996837.

Efficacy of endometrial receptivity testing for recurrent implantation failure in patients with euploid embryo transfers: study protocol for a randomized controlled trial

BACKGROUND

Embryo implantation remains a critical barrier in assisted reproductive technologies. One of the main causes of unsuccessful embryo implantation is window of implantation (WOI) displacement, particularly in patients with recurrent implantation failure (RIF). Therefore, a reliable diagnostic tool for identifying the optimal WOI is essential. Previous data has suggested that a novel RNA-Seq-based endometrial receptivity testing (ERT) can diagnose WOI, guide personalized embryo transfer (pET), and improve pregnancy outcomes in patients with RIF compared to standard embryo transfer (sET). However, there is still a lack of evidence from randomized controlled trials (RCT) with sufficient power to determine whether pET based on ERT can increase the rate of live births as the primary outcome.

METHODS

This trial is a prospective, single-blind, parallel-group RCT (1:1 ratio of pET versus sET). Infertile women with RIF who intend to undergo frozen-thawed embryo transfer (FET) after preimplantation genetic testing for aneuploidy (PGT-A) with the availability of at least one euploid blastocyst for transfer will be enrolled and assigned into two parallel groups randomly. Participants in the intervention group will undergo ERT and then pET based on the results of ERT, while those in the control group will undergo sET. The primary outcome is live birth rate.

DISCUSSION

The findings of this study will provide evidence for the effect of pET guided by ERT on pregnancy outcomes in patients with RIF.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR2100049041. Registered on 20 July 2021.

To Test or Not to Test: Routine Thrombophilia Diagnostic Screening of Women with Reproductive Failures

BACKGROUND

Recurrent reproductive failure is a global health issue affecting a significant number of women. Thrombophilias have been implicated as a possible cause. Inherited thrombophilias include a single nucleotide variant on factor V Leiden and prothrombin.

OBJECTIVE

The aim of this study was to evaluate the association between the following single nucleotide variants: factor V Leiden (c.1601G>A), the prothrombin gene (c.*97G>A) and the reproductive failure in the Polish population.

METHODS

The study was conducted in a group of 545 patients with recurrent pregnancy loss, RPL (≥2 miscarriages), and in a group of 641 patients with infertility. The distribution of genotypes for the selected variants were determined by RFLP-PCR and by the real-time PCR method.

RESULTS

A variant of the F5 gene was found in 5.14% of patients with RPL and in 6.08% of infertile women. A variant of the F2 gene was identified in 0.73% of patients with RPL and in 2.03% of women with infertility. The frequency in the study groups did not differ from that in the general population. No association between the studied variants of the F5 gene or the F2 gene and the predisposition to reproductive wastage was found.

CONCLUSIONS

Recommendations for routine thrombophilia testing in women with recurrent miscarriages should be revisited. The decision regarding testing should be made individually depending on additional factors indicating an increased risk of venous thromboembolism.

A Controversial Old Topic Revisited: Should Diagnostic Hysteroscopy Be Routinely Performed Prior to the First IVF Cycle? A Systematic Review and Updated Meta-analysis

OBJECTIVE

This systematic review and meta-analysis aimed to analyze the impact of performing diagnostic hysteroscopy before the first in vitro fertilization (IVF) cycle on the clinical pregnancy rate and live birth.

DATA SOURCES

PubMed-MEDLINE, Embase, Web of Science, The Cochrane Library, Gynecology and Fertility Specialized Register of Controlled Trials, and Google Scholar were consulted from inception to June 2022 using combinations of the relevant Medical Subject Headings terms and keywords. The search included major clinical trial registries such as ClinicalTrials.gov and the European EudraCT registry without language restrictions. In addition, manual cross-reference searches were also performed.

METHODS OF STUDY SELECTION

All randomized and controlled clinical trials, prospective and retrospective cohort studies, and case-control studies comparing the probability of pregnancy and live birth among patients who underwent diagnostic hysteroscopy with possible treatment of any abnormal findings before the IVF cycle and patients who underwent the IVF cycle directly have been considered for inclusion. Studies with insufficient information on the results of interest or without the necessary information to perform the pooled analysis, those without a control group or with end points considered different than those of interest, were excluded. The review protocol was registered in PROSPERO (CRD42022354764).

TABULATION, INTEGRATION, AND RESULTS

A total of 12 studies were included in the quantitative synthesis, reporting the reproductive outcomes of 5056 patients undergoing ART treatment for the first time. Selected studies included 6 randomized controlled trials, 1 prospective cohort study, 3 retrospective cohort studies, and 2 case-control studies. The likelihood of clinical pregnancy of patients undergoing hysteroscopy before IVF was significantly higher than those without hysteroscopy (odds ratio [OR], 1.49; 95% confidence CI 1.16-1.91; I2 = 69%). (odds ratio [OR], 1.51; 95% confidence interval [CI], 1.22-1.88; I2 59%). Eight studies included live birth rate; no statistically significant differences were found between the 2 groups for this outcome (OR,1.24; 95% CI, 0.94-1.64; I2 = 62%). Subsequently, a sensitivity analysis was performed, including only randomized clinical trials. Clinical pregnancy OR of patients undergoing hysteroscopy before starting the IVF cycle remained significantly higher than the control group (OR,1.62, 95% CI, 1.15-2.29; I2 = 62%). Risk of bias assessment was performed using the Grading of Recommendations Assessment, Development, and Evaluation.

CONCLUSION

The available scientific evidence suggests that performing routine hysteroscopy before the first IVF attempt improves the clinical pregnancy rate; however, the live birth rate is unaffected.

Immunobiology of pregnancy: from basic science to translational medicine

Embryo implantation failure and spontaneous abortions represent the main causes of infertility in developed countries. Unfortunately, incomplete knowledge of the multiple factors involved in implantation and fetal development keeps the success rate of medically assisted procreation techniques relatively low. According to recent literature, cellular and molecular mechanisms of 'immunogenic tolerance' towards the embryo are crucial to establish an 'anti-inflammatory' state permissive of a healthy pregnancy. In this review we dissect the role played by the immune system in the endometrial-embryo crosstalk, with a particular emphasis towards the fork-head-box-p3 (Foxp3+) CD4+CD25+ regulatory T (Treg) cells and discuss the most recent therapeutic advances in the context of early immune-mediated pregnancy loss.

ESHRE good practice recommendations on recurrent implantation failure

STUDY QUESTION

How should recurrent implantation failure (RIF) in patients undergoing ART be defined and managed?

SUMMARY ANSWER

This is the first ESHRE good practice recommendations paper providing a definition for RIF together with recommendations on how to investigate causes and contributing factors, and how to improve the chances of a pregnancy.

WHAT IS KNOWN ALREADY

RIF is a challenge in the ART clinic, with a multitude of investigations and interventions offered and applied in clinical practice, often without biological rationale or with unequivocal evidence of benefit.

STUDY DESIGN SIZE DURATION

This document was developed according to a predefined methodology for ESHRE good practice recommendations. Recommendations are supported by data from the literature, if available, and the results of a previously published survey on clinical practice in RIF and the expertise of the working group. A literature search was performed in PubMed and Cochrane focussing on 'recurrent reproductive failure', 'recurrent implantation failure', and 'repeated implantation failure'.

PARTICIPANTS/MATERIALS SETTING METHODS

The ESHRE Working Group on Recurrent Implantation Failure included eight members representing the ESHRE Special Interest Groups for Implantation and Early Pregnancy, Reproductive Endocrinology, and Embryology, with an independent chair and an expert in statistics. The recommendations for clinical practice were formulated based on the expert opinion of the working group, while taking into consideration the published data and results of the survey on uptake in clinical practice. The draft document was then open to ESHRE members for online peer review and was revised in light of the comments received.

MAIN RESULTS AND THE ROLE OF CHANCE

The working group recommends considering RIF as a secondary phenomenon of ART, as it can only be observed in patients undergoing IVF, and that the following description of RIF be adopted: 'RIF describes the scenario in which the transfer of embryos considered to be viable has failed to result in a positive pregnancy test sufficiently often in a specific patient to warrant consideration of further investigations and/or interventions'. It was agreed that the recommended threshold for the cumulative predicted chance of implantation to identify RIF for the purposes of initiating further investigation is 60%. When a couple have not had a successful implantation by a certain number of embryo transfers and the cumulative predicted chance of implantation associated with that number is greater than 60%, then they should be counselled on further investigation and/or treatment options. This term defines clinical RIF for which further actions should be considered. Nineteen recommendations were formulated on investigations when RIF is suspected, and 13 on interventions. Recommendations were colour-coded based on whether the investigations/interventions were recommended (green), to be considered (orange), or not recommended, i.e. not to be offered routinely (red).

LIMITATIONS REASONS FOR CAUTION

While awaiting the results of further studies and trials, the ESHRE Working Group on Recurrent Implantation Failure recommends identifying RIF based on the chance of successful implantation for the individual patient or couple and to restrict investigations and treatments to those supported by a clear rationale and data indicating their likely benefit.

WIDER IMPLICATIONS OF THE FINDINGS

This article provides not only good practice advice but also highlights the investigations and interventions that need further research. This research, when well-conducted, will be key to making progress in the clinical management of RIF.

STUDY FUNDING/COMPETING INTERESTS

The meetings and technical support for this project were funded by ESHRE. N.M. declared consulting fees from ArtPRED (The Netherlands) and Freya Biosciences (Denmark); Honoraria for lectures from Gedeon Richter, Merck, Abbott, and IBSA; being co-founder of Verso Biosense. He is Co-Chief Editor of Reproductive Biomedicine Online (RBMO). D.C. declared being an Associate Editor of Human Reproduction Update, and declared honoraria for lectures from Merck, Organon, IBSA, and Fairtility; support for attending meetings from Cooper Surgical, Fujifilm Irvine Scientific. G.G. declared that he or his institution received financial or non-financial support for research, lectures, workshops, advisory roles, or travelling from Ferring, Merck, Gedeon-Richter, PregLem, Abbott, Vifor, Organon, MSD, Coopersurgical, ObsEVA, and ReprodWissen. He is an Editor of the journals Archives of Obstetrics and Gynecology and Reproductive Biomedicine Online, and Editor in Chief of Journal Gynäkologische Endokrinologie. He is involved in guideline developments and quality control on national and international level. G.L. declared he or his institution received honoraria for lectures from Merck, Ferring, Vianex/Organon, and MSD. He is an Associate Editor of Human Reproduction Update, immediate past Coordinator of Special Interest Group for Reproductive Endocrinology of ESHRE and has been involved in Guideline Development Groups of ESHRE and national fertility authorities. D.J.M. declared being an Associate Editor for Human Reproduction Open and statistical Advisor for Reproductive Biomedicine Online. B.T. declared being shareholder of Reprognostics and she or her institution received financial or non-financial support for research, clinical trials, lectures, workshops, advisory roles or travelling from support for attending meetings from Ferring, MSD, Exeltis, Merck Serono, Bayer, Teva, Theramex and Novartis, Astropharm, Ferring. The other authors had nothing to disclose.

DISCLAIMER

This Good Practice Recommendations (GPR) document represents the views of ESHRE, which are the result of consensus between the relevant ESHRE stakeholders and are based on the scientific evidence available at the time of preparation. ESHRE GPRs should be used for information and educational purposes. They should not be interpreted as setting a standard of care or be deemed inclusive of all proper methods of care, or be exclusive of other methods of care reasonably directed to obtaining the same results. They do not replace the need for application of clinical judgement to each individual presentation, or variations based on locality and facility type. Furthermore, ESHRE GPRs do not constitute or imply the endorsement, or favouring, of any of the included technologies by ESHRE.

Prednisone vs Placebo and Live Birth in Patients With Recurrent Implantation Failure Undergoing In Vitro Fertilization: A Randomized Clinical Trial

Importance

Implantation failure remains a critical barrier to in vitro fertilization. Prednisone, as an immune-regulatory agent, is widely used to improve the probability of implantation and pregnancy, although the evidence for efficacy is inadequate.

Objective

To determine the efficacy of 10 mg of prednisone compared with placebo on live birth among women with recurrent implantation failure.

Design, Setting, and Participants

A double-blind, placebo-controlled, randomized clinical trial conducted at 8 fertility centers in China. Eligible women who had a history of 2 or more unsuccessful embryo transfer cycles, were younger than 38 years when oocytes were retrieved, and were planning to undergo frozen-thawed embryo transfer with the availability of good-quality embryos were enrolled from November 2018 to August 2020 (final follow-up August 2021).

Interventions

Participants were randomized (1:1) to receive oral pills containing either 10 mg of prednisone (n = 357) or matching placebo (n = 358) once daily, from the day at which they started endometrial preparation for frozen-thawed embryo transfer through early pregnancy.

Main Outcomes and Measures

The primary outcome was live birth, defined as the delivery of any number of neonates born at 28 or more weeks' gestation with signs of life.

Results

Among 715 women randomized (mean age, 32 years), 714 (99.9%) had data available on live birth outcomes and were included in the primary analysis. Live birth occurred among 37.8% of women (135 of 357) in the prednisone group vs 38.8% of women (139 of 358) in the placebo group (absolute difference, -1.0% [95% CI, -8.1% to 6.1%]; relative ratio [RR], 0.97 [95% CI, 0.81 to 1.17]; P = .78). The rates of biochemical pregnancy loss were 17.3% in the prednisone group and 9.9% in the placebo group (absolute difference, 7.5% [95% CI, 0.6% to 14.3%]; RR, 1.75 [95% CI, 1.03 to 2.99]; P = .04). Of those in the prednisone group, preterm delivery occurred among 11.8% and of those in the placebo group, 5.5% of pregnancies (absolute difference, 6.3% [95% CI, 0.2% to 12.4%]; RR, 2.14 [95% CI, 1.00 to 4.58]; P = .04). There were no statistically significant between-group differences in the rates of biochemical pregnancy, clinical pregnancy, implantation, neonatal complications, congenital anomalies, other adverse events, or mean birthweights.

Conclusions and Relevance

Among patients with recurrent implantation failure, treatment with prednisone did not improve live birth rate compared with placebo. Data suggested that the use of prednisone may increase the risk of preterm delivery and biochemical pregnancy loss. Our results challenge the value of prednisone use in clinical practice for the treatment of recurrent implantation failure.

Trial Registration

Chinese Clinical Trial Registry Identifier: ChiCTR1800018783.

Prediction of risk factors for first trimester pregnancy loss in frozen-thawed good-quality embryo transfer cycles using machine learning algorithms

PURPOSE

Can the risk factors that cause first trimester pregnancy loss in good-quality frozen-thawed embryo transfer (FET) cycles be predicted using machine learning algorithms?

METHODS

This is a retrospective cohort study conducted at Sisli Memorial Hospital, ART and Reproductive Genetics Center, between January 2011 and May 2021. A total of 3805 good-quality FET cycles were included in the study. First trimester pregnancy loss rates were evaluated according to female age, paternal age, body mass index (BMI), diagnosis of infertility, endometrial preparation protocols (natural/artificial), embryo quality (top/good), presence of polycystic ovarian syndrome (PCOS), history of recurrent pregnancy loss (RPL), recurrent implantation failure (RIF), severe male infertility, adenomyosis and endometriosis.

RESULTS

The first trimester pregnancy loss rate was 18.2% (693/ 3805). The presence of RPL increased first trimester pregnancy loss (OR = 7.729, 95%CI = 5.908-10.142, P = 0.000). BMI, which is > 30, increased first trimester pregnancy loss compared to < 25 (OR = 1.418, 95%CI = 1.025-1.950, P = 0.033). Endometrial preparation with artificial cycle increased first trimester pregnancy loss compared to natural cycle (OR = 2.101, 95%CI = 1.630-2.723, P = 0.000). Female age, which is 35-37, increased first trimester pregnancy loss compared to < 30 (OR = 1.617, 95%CI = 1.120-2.316, P = 0.018), and female age, which is > 37, increased first trimester pregnancy loss compared to < 30 (OR = 2.286, 95%CI = 1.146-4,38, P = 0.016). The presence of PCOS increased first trimester pregnancy loss (OR = 1.693, 95%CI = 1.198-2.390, P = 0.002). The number of previous IVF cycles, which is > 3, increased first trimester pregnancy loss compared to < 3 (OR = 2.182, 95%CI = 1.708-2.790, P = 0.000).

CONCLUSIONS

History of RPL, RIF, advanced female age, presence of PCOS, and high BMI (> 30 kg/m2) were the factors that increased first trimester pregnancy loss.

Genetische Diagnostik bei ungewollt kinderlosen Paaren oder wiederholten Fehlgeburten

Etwa 10–15 % aller Paare sind ungewollt kinderlos, entweder durch das fehlende Eintreten einer Schwangerschaft oder durch rezidivierende Aborte. Nachweisbare Ursachen einer Fertilitätsstörung finden sich gleichermaßen bei Männern und bei Frauen, bei einem Drittel sind beide Partner beteiligt. Bei 5–10 % der weiblichen und 10–20 % der männlichen Patienten sind mit den derzeit etablierten diagnostischen Analysen genetische Ursachen erkennbar. Eine ätiologische Abklärung erlaubt eine fundierte Prognose und manchmal eine spezifische Therapie, sie kann auf ein erhöhtes Risiko des Auftretens kindlicher Erkrankungen hinweisen. Eine spezifische genetische Abklärung ist daher unabhängig von einer gegebenenfalls geplanten reproduktionsmedizinischen Behandlung bei allen Paaren indiziert, die länger als ein Jahr vergeblich versuchen, ein Kind zu bekommen, und bei denen keine andere Erklärung für eine Unfruchtbarkeit nachgewiesen wurde. Die genetische Diagnostik der Unfruchtbarkeit umfasst bei beiden Partnern in der Regel eine klassische Karyotypisierung zum Nachweis einer gegebenenfalls vorliegenden gonosomalen oder balancierten strukturellen Chromosomenveränderung. Dies ist insbesondere beim wiederholten Auftreten von Fehlgeburten bei beiden Partnern indiziert. Abhängig von hormonellen Befunden sollte bei Frauen ein attenuiertes adrenogenitales Syndrom bzw. bei Verdacht auf eine primäre Ovarialinsuffizienz eine FMR1-Prämutation ausgeschlossen werden. Die genetische Diagnostik des Mannes bei Azoospermie oder gegebenenfalls bei schwerer Oligozoospermie umfasst zusätzlich zur Karyotypisierung die Testung auf AZF-Mikrodeletionen (AZF Azoospermiefaktor) sowie in Abhängigkeit von den klinischen Parametern auf pathogene Varianten im CFTR-Gen als mögliche Ursache einer obstruktiven Azoospermie. Sequenzanalysen spezifischer Gene können bei Frauen und Männern mit hypogonadotropem Hypogonadismus oder bei Verdacht auf eine monogene Spermatogenesestörung in Betracht gezogen werden. Gemäß den Leitlinien und nationalen gesetzlichen Grundlagen sollten vor der genetischen Diagnostik sowie beim Nachweis genetischer Ursachen einer Infertilität mögliche Konsequenzen und die Bedeutung für zukünftige Kinder im Rahmen einer genetischen Beratung besprochen werden.

Uterine NK cells underexpress KIR2DL1/S1 and LILRB1 in reproductive failure

A significant proportion of recurrent miscarriage, recurrent implantation failure and infertility are unexplained, and these conditions have been proposed to have an etiology of immunological dysfunction at the maternal-fetal interface. Uterine Natural Killer cells (uNK) comprise three subsets and are the most numerous immune cells found in the uterine mucosa at the time of implantation. They are thought to play an important role in successful pregnancy by regulation of extravillous trophoblast (EVT) invasion and spiral artery remodelling. Here, we examine the frequency, phenotype and function of uNK1-3 from the uterine mucosa of 16 women with unexplained reproductive failure compared to 11 controls with no reproductive problems, during the window of implantation. We report that KIR2DL1/S1 and LILRB1 expression is lower in the reproductive failure group for both uNK (total uNK, uNK 2 and 3) and pNK. We also show that degranulation activity is significantly reduced in total uNK, and that TNF-α production is lower in all uNK subsets in the reproductive failure group. Taken together, our findings suggest that reproductive failure is associated with global reduction in expression of uNK receptors important for interaction with HLA-C and HLA-G on EVT during early pregnancy, leading to reduced uNK activation. This is the first study to examine uNK subsets during the window of implantation in women with reproductive failure and will serve as a platform to focus on particular aspects of phenotype and function of uNK subsets in future studies. Further understanding of uNK dysregulation is important to establish potential diagnostic and therapeutic targets in the population of women with unexplained reproductive failure.

Diagnosing chronic endometritis: when simplification fails to clarify

Reproductive immunology has grown in importance in recent years and has even developed into a discipline of its own within the field of reproductive medicine. Many aspects of reproductive failure such as repeated implantation failure or recurrent miscarriages are, meanwhile, seen as a consequence of aberrant expression of immunological factors. This is reflected by the increasing number of tests for assessing and quantifying different immune cell types as well as by a wide range of immune therapies offered to a clientele consisting of desperate patients requesting additional 'IVF tools': first, what is still usually disregarded is the enormous plasticity and fluctuation of most immune cells in the genital tract; second, their still poorly characterized functions in the endometrial cycle: further, their partially unknown role in embryo implantation and in establishing a pregnancy; and third, the fact that one of the fundamental hypotheses of reproductive immunology-of note-the Medawar concept or 'Medawar's Paradox' of semi-allogeneic graft embryo, is partially based on an erroneous assumption, i.e. the immunologic rejection and tolerance of an embryo. In the present opinion article, we comment on the diagnostic procedures and therapy approaches for chronic endometritis within the scope of reproductive medicine.

The true incidence of recurrent implantation failure

PURPOSE OF REVIEW

To review the merits and limitations of current definitions of recurrent implantation failure (RIF), how they translate into estimates of incidence and to summarize how emerging concepts of individualizing the recognition of this condition can assist in changing the way RIF is identified, studied and managed.

RECENT FINDINGS

The notion of a one size fits all definition of RIF is seen to be of limited clinical value, as the individual risk of repeated IVF failure has many determinants and causes. Novel approaches provide a means of identifying 'actionable' RIF in individual patients.

SUMMARY

Uncertainties as to what constitutes, causes and defines RIF have served to limit progress in its management. A new approach promises to permit progress from the current impasse.

The Role of Interleukins in Recurrent Implantation Failure: A Comprehensive Review of the Literature

Recurrent implantation failure (RIF) is a multifactorial condition affecting 10-15% of in vitro fertilization (IVF) couples. Data suggest that functional dysregulation of the endometrial immune system constitutes one of the main pathophysiological mechanisms leading to RIF. The aim of this article is to provide a thorough presentation and evaluation of the role of interleukins (ILs) in the pathogenesis of RIF. A comprehensive literature screening was performed summarizing current evidence. During implantation, several classes of ILs are secreted by epithelial and stromal endometrial cells, including IL-6, IL-10, IL-12, IL-15, IL-18, and the leukemia inhibitory factor. These ILs create a perplexing network that orchestrates both proliferation and maturation of uterine natural killer cells, controls the function of regulatory T and B cells inhibiting the secretion of antifetal antibodies, and supports trophoblast invasion and decidua formation. The existing data indicate associations between ILs and RIF. The extensive analysis performed herein concludes that the dysregulation of the ILs network indeed jeopardizes implantation leading to RIF. This review further proposes a mapping of future research on how to move forward from mere associations to robust molecular data that will allow an accurate profiling of ILs in turn enabling evidence-based consultancy and decision making when addressing RIF patients.

Organoids to model the endometrium: implantation and beyond

Despite advances in assisted reproductive techniques in the 4 decades since the first human birth after in vitro fertilisation, 1–2% of couples experience recurrent implantation failure, and some will never achieve a successful pregnancy even in the absence of a confirmed dysfunction. Furthermore, 1–2% of couples who do conceive, either naturally or with assistance, will experience recurrent early loss of karyotypically normal pregnancies. In both cases, embryo-endometrial interaction is a clear candidate for exploration. The impossibility of studying implantation processes within the human body has necessitated the use of animal models and cell culture approaches. Recent advances in 3-dimensional modelling techniques, namely the advent of organoids, present an exciting opportunity to elucidate the unanswerable within human reproduction. In this review, we will explore the ontogeny of implantation modelling and propose a roadmap to application and discovery.

The Impact of New Immunological Therapeutic Strategies on Recurrent Miscarriage and Recurrent Implantation Failure

Maternal-fetal immune dysregulation is one of the risk factors that increases the probability of embryo rejection and reproductive failure. The stimulation of immunological tolerance and suppression of immunological rejection are prerequisites for protecting embryos and preventing immunological attacks. Hence, it appears that immunomodulatory and immunosuppressive therapies can manage reproductive failures by controlling immune cells. The current medical literature has shown that immunotherapy approaches and cell therapy have promising results in improving pregnancy outcomes and live birth rates. These outcomes are obtained by regulating maternal immune responses, and exerting positive effects on human reproductive processes.