Prospective, randomized study of the endometrial receptivity analysis (ERA) test in the infertility work-up to guide personalized embryo transfer versus fresh transfer or deferred embryo transfer

Does endometrial receptivity array improve reproductive outcomes in euploid embryo transfer cycles? a systematic review

Besides chromosomal normality, endometrial receptivity is an important factor in determining successful pregnancies. Endometrial receptivity array (ERA), a promising endometrial receptivity test, was speculated to improve the reproductive outcomes. However, its effectiveness is controversial in clinical practice. Therefore, we conducted this review to investigate its role in in vitro fertilization (IVF) treatment. To eliminate the interference of embryo quality, we only analyzed studies that originally reported the reproductive outcomes of patients who underwent ERA-guided euploid embryo transfer (EET). Unexpectedly, it revealed that ERA could not optimize the reproductive outcomes in EET cycles, no matter in general infertile population or in patients with a history of previous failed embryo transfers.

Personalized versus standard frozen-thawed embryo transfer in IVF/ICSI cycles: a systematic review and meta-analysis

PURPOSE

To investigate whether personalized embryo transfer (pET) protocol guided by an endometrial receptivity array (ERA) can improve clinical outcomes of assisted reproduction.

METHODS

We searched PubMed, Embase, Web of Science, and the Cochrane library for studies in which analytical comparisons of outcomes of pET and standard embryo transfer (sET) groups were undertaken. The references to the included studies were also manually searched. The primary outcome was clinical pregnancy rate (CPR), and the secondary outcomes were live birth rate (LBR), human chorionic gonadotropin (HCG) positivity, biochemical pregnancy rate (BPR), miscarriage rate (MR), implantation rate (IR), and ongoing pregnancy rate (OPR).

RESULTS

Ten studies were included in the meta-analysis, including one randomized controlled trial (RCT) and nine cohort studies. We observed no significant difference in the primary outcome of CPR between the pET and sET groups in unselected patients (RR = 1.07; 95% confidence interval [CI], 0.87-1.30; P = 0.53; I2 = 89%). In terms of secondary outcomes, we likewise noted no significant differences between the groups. Further subgroup analyses indicated that the pET protocol not only significantly reduced the MR for poor-prognosis patients, but it also reduced the CPR in donor cycles, elevated the BPR for good-prognosis patients, non-preimplantation genetic testing (PGT), and programmed cycles, and decreased the proportion of women showing HCG positivity in non-PGT cycles.

CONCLUSIONS

This meta-analysis revealed that ERA appears to possess limited guidance in embryo transfer. More high-quality RCTs are therefore needed to investigate the clinical validity and feasibility of ERA in the future.

The precise determination of the window of implantation significantly improves ART outcomes

The human endometrium is receptive to the embryo for a specific period of time known as the window of implantation (WOI). During this period, the endometrium shows a specific gene expression profile suitable for endometrial function evaluation. ER Map is a molecular tool able to accurately predict endometrial receptivity status by transcriptomic analysis. In this retrospective study, including 2256 subfertile patients undergoing ART treatment, the clinical value of precise WOI determination is studied in detail. Results obtained when single embryo transfers (sET) were scheduled either within the WOI timeframe as established by ER Map, or deviating from this WOI, are assessed and compared. Data obtained showed that 34.18% (771/2256) of patients had a displaced WOI. Analysis of ART outcomes showed significantly higher pregnancy rates in transfers scheduled within the WOI predicted compared to transfers that deviated more than 12h from this WOI (44.35% vs 23.08%, p < 0.001). The deviation from the WOI had also an impact on the progression of pregnancy, with a significant increase in pregnancy loss (~ twofold) observed in transfers that deviated more than 12h from the WOI predicted. These results indicate that the precise determination of the WOI and personalised embryo transfer can significantly improve clinical outcomes.

Do endometrial natural killer and regulatory T cells differ in infertile and clinical pregnancy patients? An analysis in patients undergoing frozen embryo transfer cycles

PROBLEM

Clinical significance of endometrial and peripheral blood natural killer (NK) and regulatory T cells (Tregs) during frozen embryo transfer (FET) cycles has not been well characterized.

DESIGN

Retrospective cohort study.

METHOD OF STUDY

Endometrial tissue was collected from infertility patients prior to a frozen embryo transfer cycle as part of an endometrial receptivity analysis (ERA^® ) biopsy or endometrial scratch test. Uterine NK (uNK) and Treg cell density was compared based on pregnancy status in the subsequent frozen embryo transfer cycle. Peripheral blood was also collected from a separate cohort of patients undergoing frozen embryo transfer. Treg cell density was compared by the presence or the absence of a clinical pregnancy in each phase of the cycle.

RESULTS

In the 33 luteal phase biopsies there were more endometrial Tregs, similar uNK and a trend toward lower CD16⁺ uNK cells in women with a future ongoing clinical pregnancy compared to non-pregnant women. There were no differences in uNK and Treg density in natural scratch cycles vs programmed cycles or in non-receptive vs receptive endometrium (ERA^® cycles). In the peripheral blood analysis, the pregnant group had higher peripheral blood Tregs on the day of serum β-hCG time point when compared to the non-pregnant group.

CONCLUSION

Higher levels of endometrial Tregs and lower levels of CD16⁺ uNK cells are positive prognostic factors for infertile women prior to frozen embryo transfer. Our work on phenotypic and proportional analyses of endometrial immune cells may complement the ERA^® in predicting improved pregnancy rates in patients with implantation failure.

Novel predictive and therapeutic options for better pregnancy outcome in frozen embryo transfer cycles

Since 1978, in the first decades of in vitro fertilization (IVF), the use of ovarian hyperstimulation allowed for the development and transfer of multiple embryos. As IVF technology improved, the number of multiple pregnancies increased, which led to gradual reduction in the number of embryos that were transferred. Embryo freezing (vitrification) was recommended to allow subsequent transfer if the fresh cycle was unsuccessful. However, experimentation has continued to improve pregnancy outcomes. We discuss here the significance of frozen embryo transfer cycle and the impact of uterine and peripheral immunity dominated by NK cells and regulatory T cells and human chorionic gonadotropin on pregnancy outcome in this innovative mode of IVF therapy.

In vitro fertilization add-ons for the endometrium: it doesn't add-up

The probability of live birth from an in vitro fertilization (IVF) cycle is modest. Many additional treatments (add-ons) are available which promise to improve the success of IVF. This review summarizes the current evidence for common IVF add-ons which are suggested to improve endometrial receptivity. Systematic reviews of randomized controlled trials and individual trials were included. Five add-ons were included: immune therapies, endometrial scratching, endometrial receptivity array, uterine artery vasodilation, and human chorionic gonadotropin instillation. The results suggest there is no robust evidence that these add-ons are effective or safe. Many IVF add-ons are costly, consuming precious resources which may be better spent on evidence-based treatments or further IVF. Large randomized controlled trials and appropriate safety assessment should be mandatory before the introduction of IVF add-ons into routine practice.

Diagnostic and therapeutic options in recurrent implantation failure

Recurrent implantation failure (RIF) is an uncommon, imprecisely defined clinical disorder characterized by failure to achieve pregnancy after repeated embryo transfers. The diverse etiologies and incomplete understanding of RIF provide significant diagnostic and therapeutic challenges to patients and providers. Careful clinical evaluation prior to assisted reproduction can uncover many treatable causes, including thyroid dysfunction, submucosal myomas, and tobacco use. The more-subtle causes often require a more-targeted assessment. Undetected, small polyps or small areas of intrauterine synechiae are relatively common and easily treated contributors to RIF. Molecular and cellular abnormalities pose a greater therapeutic challenge. Putative causes of RIF, including progesterone resistance, shifted window of receptivity, decreased integrin expression, and immunologic disturbances, should be considered in the evaluation of a patient with otherwise unexplained RIF. It may also be true that a more complex and standardized definition of RIF would be helpful in these cases. In this paper, we review the diagnostic and therapeutic approaches to RIF, with emphasis on disorders of endometrial receptivity.

Implantation failure of endometrial origin: what is new?

PURPOSE OF REVIEW

To review recent findings related to possible causes of recurrent implantation failure of endometrial origin in normal uterus.

RECENT FINDINGS

Recent evidences suggest that in apparently normal endometria, RIF may associate with molecular and functional changes in the uterus such as abnormal endometrial microbiota, including the presence of chronic endometritis, poor synchronization between the blastocyst and endometrium, and/or excessive uterine peristalsis. An altered endometrial microbiota detected by molecular techniques has been recently related to poorer embryo implantation, even in apparently normal endometria. The use of the endometrial receptivity analysis test to obtain an objective signature of endometrial receptivity has shown to improve the reproductive performance in RIF patients. The diagnosis of uterine peristalsis, however, remains challenging since the usual evaluation by transvaginal ultrasound is not accurate, and drugs tested to reduce uterine peristalsis and enhance embryo implantation have not been clearly beneficial. Finally, endometrial injury to improve implantation rates remains controversial being definitive well-designed trials needed to assess its benefit, if any.

SUMMARY

In recurrent implantation failure of endometrial origin an altered pattern of the microbial endometrial ecosystem, a displaced window of implantation leading to desynchronization between the blastocyst and the endometrium, or an altered pattern of uterine contractions during embryo transfer may be factors to consider in our attempt to solve this clinical issue. New diagnostics for assessing these conditions and new therapies to improve these dysfunctional situations are currently under investigation to be presumably included in the near future in the work-up of affected patients.

Implantation failure of endometrial origin: it is not pathology, but our failure to synchronize the developing embryo with a receptive endometrium

Repeated implantation failure (RIF) is an intriguing, massive failure of reproductive treatment in otherwise healthy women leading to the introduction of empirical adjuvant interventions that are costly, inefficient, and frustrating for our patients. In this article, we will try to convince the readers that RIF is neither a stigma nor a mysterious pathology but rather our failure to diagnose and properly synchronize the euploid blastocyst with the patient's personalized window of implantation.