Is endometriosis due to evolutionary maladaptation?

Similar to diabetes and unlike many pathogen-induced diseases, endometriosis is likely a result of maladaptation to the evolutionary heritage of humans. The objective of this article is to review the literature and improve understanding of the evolutionary factors behind endometriosis, leading to more effective prevention and treatment approaches. In primates, spontaneous decidualization of the endometrium evolved to ensure optimal implantation of a limited number of early embryos, unlike many non-primates which depend on early embryos to induce decidualization and subsequent pregnancy. Spontaneous decidualization results in menstrual bleeding when embryo implantation does not occur, and endometriosis is commonly believed to be caused by retrograde menstruation. Although direct evidence is lacking, it is likely that hunter-gatherer women experienced fewer menstrual periods due to pregnancy shortly after menarche, followed by repeated pregnancies and lactation. However, the mismatch between the evolved uterine physiology and rapid societal changes has led to modern women delaying pregnancy and experiencing numerous menstrual periods, potentially increasing the incidence of endometriosis. The symptoms of endometriosis are often managed by suppressing menstruation through systemic hormonal treatments, but these may have side effects. For patients with a family history of endometriosis or in the early stages of the disease, intrauterine devices releasing progesterone locally could prevent uterine bleeding and the development of endometriosis while preserving fertility and minimizing side effects.

Platelet-rich plasma infusion as an adjunct treatment for persistent thin lining in frozen embryo transfer cycles: first US experience report.

PURPOSE: To study effect of intrauterine infusion of platelet-rich plasma (PRP) on endometrial growth in the setting of thin endometrial lining in patients with prior cancelled or failed frozen embryo transfer (FET) cycles. MATERIALS AND METHODS: Single-arm cohort study of forty-six patients (51 cycles) with endometrial lining thickness (EMT) < 6 mm in prior cancelled or failed FET cycles requesting intrauterine PRP treatment in upcoming FET cycle. The primary outcomes were final EMT in FET cycle and change in EMT after PRP. The secondary outcomes were overall pregnancy rate, clinical pregnancy rate, miscarriage rate, ongoing pregnancy, and live birth rates. RESULTS: The mean pre-PRP EMT in all FET cycles was 4.0 ± 1.1 mm, and mean post-PRP EMT (final) was 7.1 ± 1.0 mm. Of 51 cycles, 33 (64.7%) reached ≥ 7 mm after PRP administration. There was a significant difference between pre-PRP EMT and post-PRP EMT in all FET cycles, with mean difference of 3.0 ± 1.5 mm. Three cycles were cancelled for failure to reach adequate lining. Total pregnancy rate was 72.9% in our cohort of 48 cycles that proceeded to transfer. Clinical pregnancy rate was 54.2% (26/48 FET cycles); clinical miscarriage rate was 14.3% (5/35 pregnancies). Twenty six women had live birth (18 with EMT ≥ 7 mm and 8 with EMT < 7 mm). Response to PRP was not correlated with any pre-cycle characteristics. CONCLUSION: We demonstrate a significant improvement in lining thickness and pregnancy rates in this challenging cohort of women after PRP infusion, with no adverse events. Cost-effectiveness of PRP with benefits and alternatives should be carefully considered.

Molecular Determinants of Uterine Receptivity: Comparison of Successful Implantation, Recurrent Miscarriage, and Recurrent Implantation Failure.

Embryo implantation is one of the most remarkable phenomena in human reproduction and is not yet fully understood. Proper endometrial function as well as a dynamic interaction between the endometrium itself and the blastocyst-the so-called embryo-maternal dialog-are necessary for successful implantation. Several physiological and molecular processes are involved in the success of implantation. This review describes estrogen, progesterone and their receptors, as well as the role of the cytokines interleukin (IL)-6, IL-8, leukemia inhibitory factor (LIF), IL-11, IL-1, and the glycoprotein glycodelin in successful implantation, in cases of recurrent implantation failure (RIF) and in cases of recurrent pregnancy loss (RPL). Are there differences at the molecular level underlying RIF or RPL? Since implantation has already taken place in the case of RPL, it is conceivable that different molecular biological baseline situations underlie the respective problems.

Live birth rate following endometrial preparation with daily versus depot GnRH agonist.

BACKGROUND: Gonadotrophin-releasing hormone agonist (GnRHa) downregulates gonadotropin secretion in the pituitary gland. It is used both in ovulation induction protocols and in artificial endometrium preparation. Frozen-thawed embryo transfer to artificially prepared endometrium (FET-APE) is a frequent procedure in vitro fertilization (IVF) which requires GnRHa. It can be used either as a daily low-dose injection or as a single depot injection. It is unclear which of these two regimens is superior for artificial endometrium preparation. METHODS: We evaluated the data of 72 patients who had undergone frozen embryo transfer following the 5th day Preimplantation Genetic Test-aneuploidy (PGT-A) between 2018-2021. All embryos were genetically screened, and euploid single embryos were transferred. Group 1 (n: 36) used depot GnRHa, and Group 2 (n: 36) used single daily injections for artificial endometrial preparation. The outcomes for Beta Human Chorionic Gonadotrophin (BHCG) positivity and live birth rates (LBR) was compared. RESULTS: The BHCG positivity for Group 1 and Group 2 was 75% and 80.6%, respectively. The LBR for Group 1 and Group 2 were found to be 58.3% and 63.9%, respectively. There was no statistically significant differences between the two groups. CONCLUSIONS: In artificial endometrium preparation, depot GnRHa offers cheaper and more convenient alternative to single daily dose injections, particularly in busy clinical settings.

Gonadotrophin-releasing hormone agonist (GnRHa) is used to Frozen­thawed embryo transfer to artificially prepared endometrium (FET-APE). However, it is not known which of the depot and daily preparations is more effective. Our study to exclusively compare 5th day euploid single embryos transferred in FET-APE cycles using depot or daily injections of GnRHa to avoid any influences of oocyte or spermatozoa dependent factors on Beta Human Chorionic Gonadotrophin (BHCG) positivity and live birth rates (LBR). The results were similar. Since the results are similar, the depot GnRHa form can be preferred for ease of use. However, future studies on larger series and patients with different clinical characteristics may effects the results.

Mechanisms of Regeneration and Fibrosis in the Endometrium.

The uterine lining (endometrium) regenerates repeatedly over the life span as part of its normal physiology. Substantial portions of the endometrium are shed during childbirth (parturition) and, in some species, menstruation, but the tissue is rapidly rebuilt without scarring, rendering it a powerful model of regeneration in mammals. Nonetheless, following some assaults, including medical procedures and infections, the endometrium fails to regenerate and instead forms scars that may interfere with normal endometrial function and contribute to infertility. Thus, the endometrium provides an exceptional platform to answer a central question of regenerative medicine: Why do some systems regenerate while others scar? Here, we review our current understanding of diverse endometrial disruption events in humans, nonhuman primates, and rodents, and the associated mechanisms of regenerative success and failure. Elucidating the determinants of these disparate repair processes promises insights into fundamental mechanisms of mammalian regeneration with substantial implications for reproductive health.

Protein glycosylation: bridging maternal-fetal crosstalk during embryo implantation†.

Infertility is a challenging health problem that affects 8-15% of couples worldwide. Establishing pregnancy requires successful embryo implantation, but about 85% of unsuccessful pregnancies are due to embryo implantation failure or loss soon after. Factors crucial for successful implantation include invasive blastocysts, receptive endometrium, invasion of trophoblast cells, and regulation of immune tolerance at the maternal-fetal interface. Maternal-fetal crosstalk, which relies heavily on protein-protein interactions, is a critical factor in implantation that involves multiple cellular communication and molecular pathways. Glycosylation, a protein modification process, is closely related to cell growth, adhesion, transport, signal transduction, and recognition. Protein glycosylation plays a crucial role in maternal-fetal crosstalk and can be divided into N-glycosylation and O-glycosylation, which are often terminated by sialylation or fucosylation. This review article examines the role of protein glycosylation in maternal-fetal crosstalk based on two transcriptome datasets from the GEO database (GSE139087 and GSE113790) and existing research, particularly in the context of the mechanism of protein glycosylation and embryo implantation. Dysregulation of protein glycosylation can lead to adverse pregnancy outcomes, such as missed abortion and recurrent spontaneous abortion, underscoring the importance of a thorough understanding of protein glycosylation in the diagnosis and treatment of female reproductive disorders. This knowledge could have significant clinical implications, leading to the development of more effective diagnostic and therapeutic approaches for these conditions.

Review: Endometrial function in pregnancy establishment in cattle.

The endometrium is fundamentally required for successful pregnancy in ruminants and species where the posthatching conceptus undergoes a protracted elongation and peri-implantation phase of pregnancy. Moreover, there are substantial waves of pregnancy loss during this pre- and peri-implantation period of pregnancy the precise source of which has not been clearly defined i.e., the maternal uterine contribution to this loss. Understanding the molecular interactions required for successful pregnancy in cattle will allow us to intervene to support pregnancy success during this vulnerable window. The endometrium contributes to most key developmental milestones of pregnancy establishment, including (1) contributing to the regulation of the oestrus cycle, (2) nourishing the preimplantation conceptus, (3) responding to the conceptus to create a more receptive microenvironment, (4) providing essential biophysical support, and (5) signalling and producing factors which affect the mother systemically. This review will summarise what we currently know about conceptus-maternal interactions as well as identify the gaps in our knowledge that could be filled with newer in vitro model approaches. These include the use of microfluidics, organ-on-a-chip devices, and bioinformatic approaches. This will help maximise food production efficiency (both meat and dairy) and decrease the environmental burden, while enhancing our understanding of the fundamental processes required for successful implantation in cattle.

Current perspectives on endometrial receptivity: A comprehensive overview of etiology and treatment.

Recurrent implantation failure (RIF) remains a challenging problem in assisted reproductive technology (ART). Further insights into uterine abnormalities that can disturb embryo implantation should be obtained. This review provides an overview of the effects of organic and non-organic uterine disorders on endometrial receptivity. The results suggest that various uterine pathologies can lead to defective embryo implantation via multiple mechanisms. In particular, uterine adenomyosis dysregulates molecular and cellular interactions that are vital for successful embryo implantation with a background of chronic inflammation, which may be alleviated by pretreatment with a gonadotropin-releasing hormone agonist. Uterine myomas can cause endometrial deformation and adverse alterations in uterine contractility. Nonetheless, the effectiveness of myomectomy remains debated, and endometrial polyp removal may be considered, particularly in patients with RIF. Chronic endometritis abrogates the appropriate uterine immunological environment critical for embryo implantation. Abnormal endometrial microbiota have been suggested to influence endometrial receptivity; however, supporting evidence is currently scarce. Platelet-rich plasma therapy may be a potential treatment for thin endometria; nevertheless, further validation is required. Endometrial receptivity analysis can detect dysregulation of the window of implantation, and new non-invasive methods for predicting endometrial receptivity have recently been proposed. However, numerous issues still need to be fully clarified. Further clinical and basic studies are necessary to investigate the pathophysiology of defective endometrial receptivity and identify optimal treatments for patients undergoing ART, especially those with RIF.

Maternal and embryonic signals cause functional differentiation of luminal epithelial cells and receptivity establishment.

Embryo implantation requires temporospatial maternal-embryonic dialog. Using single-cell RNA sequencing for the uterus from 2.5 to 4.5 days post-coitum (DPC) and bulk sequencing for the corresponding embryos of 3.5 and 4.0 DPC pregnant mice, we found that estrogen-responsive luminal epithelial cells (EECs) functionally differentiated into adhesive epithelial cells (AECs) and supporting epithelial cells (SECs), promoted by progesterone. Along with maternal signals, embryonic Pdgfa and Efna3/4 signaling activated AECs and SECs, respectively, enhancing the attachment of embryos to the endometrium and furthering embryo development. This differentiation process was largely conserved between humans and mice. Notably, the developmental defects of SOX9-positive human endometrial epithelial cells (similar to mouse EEC) were related to thin endometrium, whereas functional defects of SEC-similar unciliated epithelial cells were related to recurrent implantation failure (RIF). Our findings provide insights into endometrial luminal epithelial cell development directed by maternal and embryonic signaling, which is crucial for endometrial receptivity.

Endometrial receptivity in women of advanced age: an underrated factor in infertility.

BACKGROUND: Modern lifestyle has led to an increase in the age at conception. Advanced age is one of the critical risk factors for female-related infertility. It is well known that maternal age positively correlates with the deterioration of oocyte quality and chromosomal abnormalities in oocytes and embryos. The effect of age on endometrial function may be an equally important factor influencing implantation rate, pregnancy rate, and overall female fertility. However, there are only a few published studies on this topic, suggesting that this area has been under-explored. Improving our knowledge of endometrial aging from the biological (cellular, molecular, histological) and clinical perspectives would broaden our understanding of the risks of age-related female infertility. OBJECTIVE AND RATIONALE: The objective of this narrative review is to critically evaluate the existing literature on endometrial aging with a focus on synthesizing the evidence for the impact of endometrial aging on conception and pregnancy success. This would provide insights into existing gaps in the clinical application of research findings and promote the development of treatment options in this field. SEARCH METHODS: The review was prepared using PubMed (Medline) until February 2023 with the keywords such as 'endometrial aging', 'receptivity', 'decidualization', 'hormone', 'senescence', 'cellular', 'molecular', 'methylation', 'biological age', 'epigenetic', 'oocyte recipient', 'oocyte donation', 'embryo transfer', and 'pregnancy rate'. Articles in a language other than English were excluded. OUTCOMES: In the aging endometrium, alterations occur at the molecular, cellular, and histological levels suggesting that aging has a negative effect on endometrial biology and may impair endometrial receptivity. Additionally, advanced age influences cellular senescence, which plays an important role during the initial phase of implantation and is a major obstacle in the development of suitable senolytic agents for endometrial aging. Aging is also accountable for chronic conditions associated with inflammaging, which eventually can lead to increased pro-inflammation and tissue fibrosis. Furthermore, advanced age influences epigenetic regulation in the endometrium, thus altering the relation between its epigenetic and chronological age. The studies in oocyte donation cycles to determine the effect of age on endometrial receptivity with respect to the rates of implantation, clinical pregnancy, miscarriage, and live birth have revealed contradictory inferences indicating the need for future research on the mechanisms and corresponding causal effects of women's age on endometrial receptivity. WIDER IMPLICATIONS: Increasing age can be accountable for female infertility and IVF failures. Based on the complied observations and synthesized conclusions in this review, advanced age has been shown to have a negative impact on endometrial functioning. This information can provide recommendations for future research focusing on molecular mechanisms of age-related cellular senescence, cellular composition, and transcriptomic changes in relation to endometrial aging. Additionally, further prospective research is needed to explore newly emerging therapeutic options, such as the senolytic agents that can target endometrial aging without affecting decidualization. Moreover, clinical trial protocols, focusing on oocyte donation cycles, would be beneficial in understanding the direct clinical implications of endometrial aging on pregnancy outcomes.

Human embryo implantation.

Embryo implantation in humans is interstitial, meaning the entire conceptus embeds in the endometrium before the placental trophoblast invades beyond the uterine mucosa into the underlying inner myometrium. Once implanted, embryo survival pivots on the transformation of the endometrium into an anti-inflammatory placental bed, termed decidua, under homeostatic control of uterine natural killer cells. Here, we examine the evolutionary context of embryo implantation and elaborate on uterine remodelling before and after conception in humans. We also discuss the interactions between the embryo and the decidualising endometrium that regulate interstitial implantation and determine embryo fitness. Together, this Review highlights the precarious but adaptable nature of the implantation process.

Predictive Value of Endometrial Receptivity for Pregnancy Outcomes of In-vitro Fertilization Embryo Transfer for Patients of Different Ages.

Context: In recent years, the number of women with unexplained infertility has increased, and clinicians consider poor endometrial receptivity (ER) to be one of the main reasons. ER can have great predictive value for in-vitro fertilization embryo transfer (IVF-ET)-induced pregnancy. Objective: The study intended to investigate the predictive value of ER-endometrial thickness (EMT) and type and hemodynamic parameters-using color-doppler ultrasound on the pregnancy outcome of IVF-ET for women of different ages. Design: The research team performed a prospective controlled study. Setting: The study took place at the Department of Reproductive Medicine at Hebei Reproductive Hospital in Shijiazhuang, China. Participants: Participants were 841 infertile patients undergoing IVF-ET treatment at the hospital between March 01, 2018 and December 30, 2018. The research team divided participants into two groups: (1) participants diagnosed as having a clinical pregnancy after IVF-ET became the pregnancy group, with 439 participants, and (2) participants who didn't become pregnant became the nonpregnancy group, with 402 participants. Outcome Measures: The research team: (1) measured EMT, (2) determined endometrium types, (3) classified the intimal and subintimal blood flow, and (4) determined the hemodynamic parameters of the endometrium and subendometrium. The team also measured: (1) the systolic blood flow velocity (VS), (2) diastolic blood flow velocity (VD), and (3) average blood flow velocity (VM) three times and recorded the average value. Results: Statistically significant differences existed in the pregnancy and implantation rates among the different age groups for the groups with EMTs of <8 mm and 8-13 mm (P < .05). The results were similar in the endometrial Type A and endometrial Type B groups as well as between the endometrial blood flow Type 1 and Type 2 groups (P < .05). The distribution of endometrial blood flow types was significantly different between the groups (P = .002). In addition, statistically significant differences existed in the implantation rates between the <30 years and 30-34 groups in different blood-flow-type groups (P < .05). Based on the results of the ROC curve, high-quality embryos (0.566, 95%CI: 0.527-0.605) and endometrial blood flow types (0.554, 95%CI: 0.515-0.593) could not predict clinical pregnancy. Conclusions: The pregnancy and implantation rates increased between the <30 and 30-34 age groups and them decreased between the age groups as age increased. EMT, endometrial type, and blood flow type can be valuable parameters in predicting the implantation and pregnancy rates of patients of different ages.

Unveiling uterine aging: Much more to learn.

Uterine aging is an important factor that impacts fertility, reproductive health, and uterus-related diseases; however, it remains poorly explored. Functionally, these disturbances have been associated with an abnormal hormonal response in the endometrium and decreased endometrial receptivity. Based on emerging evidence, these alterations are mediated via the senescence of endometrial stem cells and impaired decidualization of endometrial stromal cells. Multiple molecular activities may participate in uterine aging, including oxidative stress, inflammation, fibrosis, DNA damage response, and cellular senescence. Over the past decade, several protective strategies targeting these biological processes have afforded promising results, including stem cell therapy, anti-aging drugs, and herbal medicines. However, the currently available evidence is fragmented and scattered. Here, we summarize the most recent findings regarding uterine aging, including functional and structural alterations and potential cellular and molecular mechanisms, and discuss potential protective interventions against uterine aging. Thereby, we hope to provide a comprehensive understanding of the pathophysiological processes and underlying mechanisms associated with uterine aging, as well as improve fecundity and reproductive outcomes in females of advanced reproductive age.

Agonist long protocol improves outcomes of vitrified-warmed embryo transfer in repeatedly thin endometrium.

RESEARCH QUESTION: Does follicular stimulation using human menopausal gonadotrophin (HMG) after pituitary down-regulation by a GnRH agonist improve endometrial thickness (EMT) and clinical outcomes of frozen-thawed embryo transfer (FET; using vitrified-warmed embryos) in women with thin endometrium after intensified oestrogen administration (IOA)? DESIGN: This was a retrospective study. A total of 627 patients attempted 683 FET cycles with at least one previous history of thin endometrium. None of the cycles reached over 7 mm EMT after using oral and vaginal oestradiol for more than 21 days (IOA protocol). A total of 129 cycles proceeded with FET, 305 cycles were cancelled, and 249 cycles involved administration of HMG following GnRH agonist pituitary down-regulation (GnRH agonist + HMG protocol) for further endometrial preparation. RESULTS: EMT became significantly greater (7.18 ± 1.14 mm versus 6.13 ± 0.63 mm, P < 0.001) using GnRH agonist + HMG compared with previous IOA cycles, but this was not related to serum oestrogen concentrations. A total of 213 cycles after the GnRH agonist + HMG protocol proceeded with FET, showing a significantly increased clinical pregnancy rate, implantation rate and live birth rate compared with those after IOA. CONCLUSIONS: The GnRH agonist + HMG protocol for endometrial preparation in FET cycles improves EMT in women with a thin endometrium after IOA and showed significantly better clinical outcomes than IOA. The authors suggest that the GnRH agonist + HMG protocol should be used for EMT that is less than 7 mm after there has been no optimal response to IOA.

Distinguish Characters of Luminal and Glandular Epithelium from Mouse Uterus Using a Novel Enzyme-Based Separation Method.

The uterine luminal epithelium, glandular epithelium, and stromal cells are vital for the establishment of pregnancy. Previously studies have shown various methods to isolate mouse uterine epithelium and stromal cells, including laser capture microdissection (LCM), enzyme digestion, and immunomagnetic beads. Despite the importance of the endometrial epithelium as the site of implantation and nutritional support for the conceptus, there is no isolated method to separate the luminal epithelium and glandular epithelium. Here, we establish a novel enzyme-based way to separate two types of epithelium and keep their viability. In this article, we analyzed their purity by mRNA level, immunostaining, and transcriptome analysis. Our isolation method revealed several unstudied luminal and glandular epithelial markers in transcriptome analysis. We further demonstrated the viability of the isolated epithelium by 2D and 3D cultures. The results showed that we successfully separated the endometrial luminal epithelium and glandular epithelium. We also provided an experimental model for the following study of the physiological function of the different parts of the uterus and related diseases.

Human amniotic mesenchymal stem cells promote endometrium regeneration in a rat model of intrauterine adhesion.

Human amniotic transplantation has been proposed to improve the therapeutic efficacy of intrauterine adhesions (IUAs). Human amniotic mesenchymal stem stromal cells (hAMSCs) can differentiate into multiple tissue types. This study aimed to investigate the mechanism by which hAMSCs transplantation promotes endometrial regeneration. The rat models with IUA were established through mechanical and infective methods, and PKH26-labeled hAMSCs were transplanted through the tail vein (combined with/without estrogen). Under three different conditions, hAMSCs differentiated into endometrium-like cells. HE and Mason staining assays, and immunohistochemistry were used to compare the changes in rat models treated with hAMSCs and/or estrogen transplantation. To define the induction of hAMSCs to endometrium-like cells in vitro, an induction medium (cytokines, estrogen) was used to investigate the differentiation of hAMSCs into endometrium-like cells. qRT-polymerase chain reaction (PCR) and western blotting were performed to detect the differentiation of hAMSCs into endometrium-like cells. A greater number of glands, fewer endometrial fibrotic areas, and stronger expression of vascular endothelial growth factor and cytokeratin in the combined group (hAMSCs transplantation combined with estrogen) than in the other treatment groups were observed. hAMSCs could be induced into endometrium-like cells by cytokine treatment (TGF-ß1, EGF, and PDGF-BB). Transplantation of hAMSCs is an effective alternative for endometrial regeneration after injury in rats. The differentiation protocol for hAMSCs will be useful for further studies on human endometrial regeneration.

Selected pathological conditions affecting endometrial receptivity.

OBJECTIVE: A summary of new knowledge on embryo implantation in dependence on quality of the endometrium. METHODS: Literature review from August 2022 of the relevant publications in Web of Science, Scopus and PubMed/Medline databases, focused on "endometrial receptivity", "polycystic ovary syndrome", "endometriosis", "SARS-CoV-2". RESULTS: The receptive state of the endometrium is a result of physiological remodeling and immune system activity modulated by the microbio-me. This balance can be disturbed by myomas, polyps, sactosalpings, adenomyosis, endometriosis, polycystic ovary syndrome, infections. The effect of SARS-CoV-2 infection is being discussed. For a successful implantation, timing of transfer is crucial. The ultrasound examination is used conventionally. In specific cases, hysteroscopy and endometrium bio-psy are recommended. Histological and immunohistochemical evaluation is performed together with examination of microbio-me or transcriptome. To support the implantation, gestagenes are used, or metformin in the patients with polycystic ovary syndrome. In cases of a repeated implantation failure, the intrauterine infusion of mononuclear cells or platelet rich plasma is used, subcutaneous application of granulocyte colony stimulating growth factor, intravenous application of atosiban or intrauterine application of human chorionic gonadotropin. CONCLUSION: Recent research in the field of transcriptomics, proteomics and reproductive immunology uncovers the process of implantation more deeply and opens a new stage of the assisted reproduction.

Effect of Timing by Endometrial Receptivity Testing vs Standard Timing of Frozen Embryo Transfer on Live Birth in Patients Undergoing In Vitro Fertilization: A Randomized Clinical Trial.

Importance: Endometrial receptivity testing is purported to improve live birth following frozen embryo transfer by identifying the optimal embryo transfer time for an individual patient; however, data are conflicting. Objective: To compare live birth from single euploid frozen embryo transfer according to endometrial receptivity testing vs standardized timing. Design, Setting, and Participants: Double-blind, randomized clinical trial at 30 sites within a multicenter private fertility practice in the Eastern US. Enrollment was from May 2018 to September 2020; follow-up concluded in August 2021. Participants underwent in vitro fertilization, preimplantation genetic testing for aneuploidy, endometrial receptivity testing, and frozen embryo transfer. Those with euploid blastocyst(s) and an informative receptivity result were randomized. Exclusion criteria included recurrent pregnancy loss, recurrent implantation failure, surgically aspirated sperm, donor egg(s), and unmitigated anatomic uterine cavity defects. Interventions: The intervention group (n = 381) underwent receptivity-timed frozen embryo transfer, with adjusted duration of progesterone exposure prior to transfer, if indicated by receptivity testing. The control group (n = 386) underwent transfer at standard timing, regardless of receptivity test results. Main Outcomes and Measures: The primary outcome was live birth. There were 3 secondary outcomes, including biochemical pregnancy and clinical pregnancy. Results: Among 767 participants who were randomized (mean age, 35 years), 755 (98%) completed the trial. All randomized participants were analyzed. The primary outcome of live birth occurred in 58.5% of transfers (223 of 381) in the intervention group vs 61.9% of transfers (239 of 386) in the control group (difference, -3.4% [95% CI, -10.3% to 3.5%]; rate ratio [RR], 0.95 [95% CI, 0.79 to 1.13]; P = .38). There were no significant differences in the intervention vs the control group for the prespecified secondary outcomes, including biochemical pregnancy rate (77.2% vs 79.5%, respectively; difference, -2.3% [95% CI, -8.2% to 3.5%]; RR, 0.97 [95% CI, 0.83 to 1.14]; P = .48) and clinical pregnancy rate (68.8% vs 72.8%, respectively; difference, -4.0% [95% CI, -10.4% to 2.4%]; RR, 0.94 [95% CI, 0.80 to 1.12]; P = .25). There were no reported adverse events. Conclusions and Relevance: Among patients for whom in vitro fertilization yielded a euploid blastocyst, the use of receptivity testing to guide the timing of frozen embryo transfer, compared with standard timing for transfer, did not significantly improve the rate of live birth. The findings do not support routine use of receptivity testing to guide the timing of embryo transfer during in vitro fertilization. Trial Registration: ClinicalTrials.gov Identifier: NCT03558399.

Clinical aspects of decidualization / A decidualizáció klinikai vonatkozásai

An essential component of successful conception and pregnancy is decidualization, which involves structural and functional transformation of the endometrium. The process involves structural changes in the uterine mucosa, transformation of spiral arterioles, numerical and functional adaptation of leukocytes in the endometrium and their subsequent migration, and functional and morphological changes in decidual stromal cells. As part of decidualization, trophoblast cells of embryonic origin perform a physiological invasion of maternal tissue to create the placenta. The success of the process is due to the special antigenicity of the trophoblast cells and the immune communication between the graft (fetus) and the host (mother) through hormones, cytokines and multiple receptorligand connections. Disorders of these processes are the basis of several diseases that threaten conception, implantation, and successful pregnancy, such as recurrent miscarriage, preeclampsia, intrauterine retardation, or preterm birth. In this article, we review the anatomical, immunological, and molecular basis of physiological decidualization to address common disorders in the clinical practice of obstetrics that are related to a dysfunctional decidualization.