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

Establishment of an In Vitro Embryo-Endometrium Model Using Alginate-Embedded Mouse Embryos and Human Embryoid Body

BACKGROUND

Embryo-endometrium cross-talk is one of the critical processes for implantation, and unsuccessful cross-talk leads to infertility. We established an endometrium-embryo (or embryoid bodies, hEBs) in vitro model in 2D and 3D conditions and assessed its potential through the fusion of embryos and the expression of specific markers.

METHODS

C57BL/6 mouse embryos and human embryoid body (hEB) derived from embryonic stem cells were prepared as embryo models. Mouse endometrium (EM) and human endometrium cell line, HEC-1-A, were prepared, and 2D or 3D EMs were generated. The viability of the 3D endometrium was analyzed, and the optimal ratio of the gelation was revealed. The invasion of the embryos or hEBs was examined by immunostaining and 3D image rendering.

RESULTS

The embryos and the alternative hEBs were effectively fused into 2D or 3D vitro EM models in both mouse and human models. The fused embryos and hEBs exhibited migration and further development. Notably, the established in vitro model expressed Oct4 and E-Cadherin, markers for early embryonic development; human CG Receptor and Progesterone Receptor, critical for implantation and pregnancy maintenance; and TSH Receptor, Epiregulin, and Prolactin, indicators of endometrial receptivity and embryo implantation.

CONCLUSION

This study marks a significant advancement in the field, as we have successfully established a novel in vitro model for studying embryo-endometrium cross-talk. This model, a crucial tool for understanding fertility and the causes of miscarriage due to failed implantation, provides a unique platform for investigating the complex processes of successful implantation and pregnancy, underscoring its potential impact on reproductive health.

Artificial Intelligence in Human Reproduction

The use of artificial intelligence (AI) in human reproduction is a rapidly evolving field with both exciting possibilities and ethical considerations. This technology has the potential to improve success rates and reduce the emotional and financial burden of infertility. However, it also raises ethical and privacy concerns. This paper presents an overview of the current and potential applications of AI in human reproduction. It explores the use of AI in various aspects of reproductive medicine, including fertility tracking, assisted reproductive technologies, management of pregnancy complications, and laboratory automation. In addition, we discuss the need for robust ethical frameworks and regulations to ensure the responsible and equitable use of AI in reproductive medicine.

The effect of sequential embryo transfer on pregnancy outcomes in patients with recurrent implantation failure: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

The aim of our study was to assess the impact of sequential embryo transfer on pregnancy outcomes among patients with recurrent implantation failure (RIF).

METHODS

We conducted a comprehensive search across various databases for eligible clinical trials from inception to January 2024. Randomized controlled trials (RCTs) were included if they compared sequential embryo transfer, comprising both cleavage-stage and blastocyst-stage embryos, with other transfer protocols in infertile women with repeated implantation failure. Meta-analysis was performed using Revman software. Our primary focus was on the ongoing pregnancy rate. Our secondary measures included rates of chemical pregnancies, clinical pregnancies, miscarriages, and multiple pregnancies.

RESULTS

Seven RCTs, encompassing 909 patients, met the inclusion criteria. Sequential embryo transfer demonstrated a significant increase in the ongoing pregnancy rate compared to the control group (OR = 2.28, 95% CI [1.46, 3.56], p = 0.003). Moreover, the sequential embryo transfer group exhibited notable improvements in chemical and clinical pregnancy rates. There were no statistically significant differences between the groups regarding multiple pregnancy and miscarriage rates (p > 0.05).

CONCLUSIONS

Sequential embryo transfer shows promise in enhancing pregnancy outcomes among RIF patients. However, additional trials are warranted to validate our findings.

Sequential Transfer of Blastocysts on Day 5 and Day 6 in Patients with Repeated Implantation Failure in Frozen Embryo Transfer Cycle

The aim of this study was to evaluate which frozen embryo transfer (FET) strategy benefits the recurrent implantation failure (RIF) population. A retrospective study of 336 women with RIF was performed from July 2020 to October 2023. The patients were divided into three groups according to the FET protocol. The three FET protocols included transferring a blastocyst on both days 5 and 6 (Group 1, n = 138); transferring a cleavage-stage embryo on day 3 and a blastocyst on day 5 (Group 2, n = 55); and transferring double blastocysts on day 5 (Group 3, n = 143).The sequential day 5 and day 6 blastocyst ET strategy significantly improved in vitro fertilization success rates compared with those of both the traditional double-blastocyst day 5 transfer strategy and the strategy involving one cleavage-stage embryo transfer on day 3 and one blastocyst transfer on day 5 in RIF patients. Compared with those observed in Day 5 double-blastocyst transfer, the rates of clinical pregnancy and implantation increased (51.75% vs. 64.49%, P < 0.001 and 37.06% vs. 41.3%, P = 0.005, respectively), while the rates of biochemical pregnancy and multiple gestation decreased (18.18% vs. 12.32%, P = 0.006 and 43.24% vs. 28.09%, P = 0.044, respectively) with the new protocol.Blastocysts from sequential embryo transfer on day 5 and day 6 were more effective than those from the traditional FET protocol at improving pregnancy outcomes and lowering the multiple pregnancy rate in RIF patients. When only one or zero good-quality blastocysts are available, sequential blastocyst ET on days 5 and 6 should be considered.

The Role of the Endometrium in Implantation: A Modern View

According to the current data, the endometrium acts as a "sensor" of embryo quality, which promotes the implantation of euploid embryos and prevents the implantation and/or subsequent development of genetically abnormal embryos. The present review addresses the nature of the "sensory function" of the endometrium and highlights the necessity for assessing its functional status. The first section examines the evolutionary origin of the "sensory" ability of the endometrium as a consequence of spontaneous decidualization that occurred in placental animals. The second section details the mechanisms for implementing this function at the cellular level. In particular, the recent findings of the appearance of different cell subpopulations during decidualization are described, and their role in implantation is discussed. The pathological consequences of an imbalance among these subpopulations are also discussed. Finally, the third section summarizes information on currently available clinical tools to assess endometrial functional status. The advantages and disadvantages of the approaches are emphasized, and possible options for developing more advanced technologies for assessing the "sensory" function of the endometrium are proposed.

Unraveling the H19/GAS1 axis in recurrent implantation failure: A potential biomarker for diagnosis and insight into immune microenvironment alteration

Recurrent implantation failure (RIF) presents a significant clinical challenge due to the lack of established diagnostic and therapeutic guidelines. Emerging evidence underscores the crucial role of competitive endogenous RNA (ceRNA) regulatory networks in non-cancerous female reproductive disorders, yet the intricacies and operational characteristics of these networks in RIF are not fully understood. This study aims to demystify the ceRNA regulatory network and identify potential biomarkers for its diagnosis. We analyzed expression profiles of three RNA types (long noncoding RNAs [lncRNAs], microRNAs [miRNAs], and mRNAs) sourced from the GEO database, leading to the identification of the H19-hsa-miR-301a-3p-GAS1 ceRNA network. This network demonstrates significant diagnostic relevance for RIF. Notably, the H19/GAS1 axis within this ceRNA network, identified through correlation analysis, emerged as a promising diagnostic marker, as evidenced by operating receiver operator characteristic (ROC) curve analysis. Further investigation into the binding potential of miR-301a-3p with H19 and GAS1 revealed a close association of these genes with endometrial disorders and embryo loss, as per the Comparative Toxicogenomics Database. Additionally, our immune infiltration analysis revealed a lower proportion of T cells gamma delta (γδ) in RIF, along with distinct differences in the expression of immune cell type-specific markers between fertile patients and those with RIF. We also observed a correlation between aberrant expression of H19/GAS1 and these immune markers, suggesting that the H19/GAS1 axis might play a role in modifying the immune microenvironment, contributing to the pathogenesis of RIF. In conclusion, the ceRNA-based H19/GAS1 axis holds promise as a novel diagnostic biomarker for RIF, potentially enhancing our understanding of its underlying mechanisms and improving the success rates of implantation.

The Molecular Link between Obesity and the Endometrial Environment: A Starting Point for Female Infertility

Female infertility constitutes a growing health problem in developing countries and could be associated with several possible causes including reproductive disorders, congenital malformations, infections and hormonal dysfunction. Nonetheless, a series of additional factors can also negatively impact female fertility and are represented by chronic exposure to environmental pollutants, stress, unhealthy lifestyle choices such as cigarette smoking and, among others, obesity. Excess weight is associated with several chronic diseases, and growing evidence demonstrates that it can compromise reproductive physiology due to its influence on endometrial gene expression and receptivity. Thus, the current review of the literature mainly focused on how obesity can impair uterine receptivity, mostly from a molecular point of view throughout the window of implantation (WOI) period at an endometrial level. It was also highlighted that an obesity-related increase in adipose tissue may lead to a modulation in the expression of multiple pathways, which could cause a hostile endometrial environment with a consequent negative impact on the uterine receptivity and the establishment of pregnancy. Thanks to the use of the endometrial receptivity assay (ERA), a specific microarray that studies the expression of a series of genes, it is now possible to evaluate the endometrial status of patients with infertility problems in a more detailed manner. Moreover, female fertility and endometrial receptivity could be affected by endometriosis, a chronic benign gynecological disease, whose cause-and-effect relationship to obesity is still uncertain. Therefore, further investigations would be required to better elucidate these mechanisms that govern embryo implantation and could be potentially useful for the generation of new strategies to overcome implantation failure and improve the pregnancy rates in obese women.

Feasible Influence of G-CSF on Clinical Pregnancy Outcome in Oocyte Donation Cycles for Patients with Recurrent Implantation Failure

Background and Objectives: The aim of our single-center cohort study was the determination of the influence of the intrauterine lavage of granulocyte colony-stimulating growth factor (G-CSF) on clinical pregnancy rate in patients with a history of implantation failure older than 40 years. Materials and Methods: The study was conducted in Ferticare Prague SE between May 2018 and June 2020. Overall, 115 patients were distributed into two arms, with 48 subjects in the experimental and 67 in the control arm. All women have had a previous history of unsuccessful history of infertility treatment with their own genetic material and at least one ineffective cycle with the donated oocytes. The experimental arm underwent the intrauterine lavage of 0.5 mL of pure G-CSF from 120 to 48 h prior to embryo transfer. Results: The clinical pregnancy rate was 63.3% in the experimental arm and 47.8% in the control arm (p = 0.097 for Pearsonߣs χ2, and p = 0.133 for Fisher's exact test). However, the mean endometrial thickness on the day of embryo transfer did not appear to be statistically different (p = 0.139). Only the difference in endometrium thickness growth was statistically significant (p = 0.023). The increase in pregnancy rate is still encouraging for the future, even if it is not significant. Conclusion: Our study suggests the trend of increased pregnancy rate after the intrauterine G-CSF lavage in the interval of 120-48 h prior to embryo transfer.

MiR-135a-5p regulates window of implantation by suppressing pinopodes development and decidualization of endometrial stromal cells

PURPOSE

The window of implantation (WOI) is a brief period during which the endometrium is receptive to embryo implantation. This study investigated the relationship between miR-135a-5p and endometrial receptivity.

METHODS

Peripheral blood was collected on the day of ovulation and the 5th day after ovulation for high-throughput sequencing from women who achieved clinical pregnancy through natural cycle frozen embryo transfer. RT-qPCR assessed miR-135a-5p expression in the endometrium tissue or cells during the mouse implantation window or decidualization. Scanning electron microscopy was utilized to observe pinopode morphology and quantity in mice overexpressing miR-135a-5p during the WOI. Human endometrial stromal cells (HESC) and artificial induction of mouse uterine decidualization were used to explore whether miR-135a-5p overexpression inhibits decidualization by regulating HOXA10 and BMPR2. Furthermore, the impact of miR-135a-5p on HESC proliferation and HTR8/SVneo invasion was explored.

RESULTS

A total of 54 women were enrolled in the study. bioinformatics analysis and animal models demonstrated that miR-135a-5p was significantly downregulated during the WOI, and its high expression can lead to abnormal pregnancy outcomes. Overexpression of miR-135a-5p resulted in the absence of pinopode in mouse endometrial tissue during the WOI. High miR-135a-5p levels were found to potentially inhibit endometrial tissue decidualization by downregulating HOXA10 and BMPR2 expression. Finally, CEBPD was identified as a potential regulator of miR-135a-5p, which would explain the decreased miR-135a-5p expression during the WOI.

CONCLUSION

MiR-135a-5p expression is significantly downregulated during the WOI. High miR-135a-5p levels suppress pinopode development and endometrial tissue decidualization through HOXA10 and BMPR2, contributing to inadequate endometrial receptivity.

A Comprehensive Review of the Endometrial Receptivity Array in Euploid Embryo Transfer Cycles

The Endometrial Receptivity Array (ERA) is a revolutionary molecular diagnostic tool that determines the optimal timing for embryo transfer by analyzing the gene expression profile of endometrial tissue. This comprehensive review examines the significance and application of ERA in euploid embryo transfer cycles, where the implantation of embryos with the correct number of chromosomes is critical for achieving successful pregnancy outcomes. This review underscores its role in enhancing implantation rates and reducing pregnancy loss by assessing the evolution, methodology, clinical applications, efficacy, and challenges associated with ERA. Key findings highlight ERA's superior accuracy in identifying the window of implantation compared to traditional methods, resulting in improved clinical outcomes in assisted reproductive technology (ART) cycles. Despite its benefits, the review acknowledges challenges such as cost, accessibility, and the need for standardization. Recommendations for clinical practice emphasize the integration of ERA into routine ART protocols, comprehensive patient counseling, and the importance of multidisciplinary collaboration. The review outlines promising prospects, including technological advancements to make ERA more cost-effective, the development of refined gene expression profiles, and the potential integration with other emerging ART technologies. Further research directions include long-term studies on the outcomes of ERA-guided pregnancies and exploring its application in cases of recurrent implantation failure and unexplained infertility. Overall, ERA represents a significant advancement in reproductive medicine, offering a personalized approach to embryo transfer timing that can significantly improve the success rates of euploid embryo transfers.

The Impact of Progesterone Administration Routes on Endometrial Receptivity and Clinical Outcomes in Assisted Reproductive Technology Cycles

Introduction Assisted reproductive technologies (ART) rely on endometrial receptivity (ER) for successful embryo implantation. This study aimed to compare the impact of different progesterone administration routes on ER assessed using optimal time for endometrial receptivity analysis (OpERA) and clinical outcomes in ART cycles. Methods A retrospective cohort analysis was conducted on 281 infertile women who underwent in vitro fertilization (IVF). Patients were stratified based on progesterone administration routes: oral and vaginal progesterone (Group 1) vs. intramuscular progesterone (Group 2). OpERA was performed on 257 patients to assess ER. Clinical outcomes, including biochemical pregnancy rate (BPR), clinical pregnancy rate (CPR), implantation rate (IR), and abortion rate (AR), were compared between the groups. Results OpERA results showed no significant differences between Group 1 and Group 2 in receptive (51.2% vs. 52.0%, p = 0.857), pre-receptive (44.1% vs. 44.6%, p = 0.933), or post-receptive (4.7% vs. 3.1%, p = 0.496) states. Clinical outcomes, including BPR (59.9% vs. 60.9%, p = 0.903), CPR (50.0% vs. 56.5%, p = 0.463), IR (52.5% vs. 55.3%, p = 0.748), and AR (44.3% vs. 45.6%, p = 0.882), did not significantly differ between the groups. Conclusion Progesterone administration routes did not significantly affect ER or clinical outcomes, highlighting the need to prioritize understanding and enhancing ER instead of solely focusing on progesterone delivery methods. Identifying molecular pathways or biomarkers could improve receptivity and optimize ART, ultimately improving pregnancy outcomes.

Rapid generation of functional nanovesicles from human trophectodermal cells for embryo attachment and outgrowth

Extracellular vesicles (EVs) are important mediators of embryo attachment and outgrowth critical for successful implantation. While EVs have garnered immense interest in their therapeutic potential in assisted reproductive technology by improving implantation success, their large-scale generation remains a major challenge. Here, we report a rapid and scalable production of nanovesicles (NVs) directly from human trophectoderm cells (hTSCs) via serial mechanical extrusion of cells; these NVs can be generated in approximately 6 h with a 20-fold higher yield than EVs isolated from culture medium of the same number of cells. NVs display similar biophysical traits (morphologically intact, spherical, 90-130 nm) to EVs, and are laden with hallmark players of implantation that include cell-matrix adhesion and extracellular matrix organisation proteins (ITGA2/V, ITGB1, MFGE8) and antioxidative regulators (PRDX1, SOD2). Functionally, NVs are readily taken up by low-receptive endometrial HEC1A cells and reprogram their proteome towards a receptive phenotype that support hTSC spheroid attachment. Moreover, a single dose treatment with NVs significantly enhanced adhesion and spreading of mouse embryo trophoblast on fibronectin matrix. Thus, we demonstrate the functional potential of NVs in enhancing embryo implantation and highlight their rapid and scalable generation, amenable to clinical utility.

Personalized embryo transfer guided by rsERT improves pregnancy outcomes in patients with repeated implantation failure

Introduction

Embryo implantation requires synchronous communication between the embryo and maternal endometrium. Inadequate maternal endometrial receptivity is one of the principal causes for embryo implantation failure [especially repeated implantation failure (RIF)] when biopsied good-quality euploid embryos are transferred. An RNA-seq-based endometrial receptivity test (rsERT) was previously established to precisely guide successful embryo implantation. In this study, we aimed to evaluate the effect of personalized embryo transfer (pET) via rsERT on the clinical outcomes in patients with RIF.

Methods

A total of 155 patients with RIF were included in the present retrospective study and were divided into two groups: 60 patients who underwent rsERT and pET (Group rsERT) and 95 patients who underwent standard frozen embryo transfer (FET) without rsERT (Group FET). Reproductive outcomes were compared for patients who underwent rsERT-guided pET and standard FET.

Results

Forty percent (24/60) of the patients who underwent rsERT were receptive, and the remaining 60% (36/60) were non-receptive. The positive human chorionic gonadotropin (β-hCG) rate (56.3% vs. 30.5%, P = 0.003) and clinical pregnancy rate (43.8% vs. 24.2%, P = 0.017) were significantly higher in Group rsERT patients than in FET group patients. Additionally, Group rsERT patients also showed a higher implantation rate (32.1% vs. 22.1%, P = 0.104) and live birth rate (35.4% vs. 21.1%, P = 0.064) when compared with FET patients, although without significance. For subpopulation analysis, the positive β-hCG rate, clinical pregnancy rate, implantation rate, and live birth rate of receptive patients were not statistically significant different from those of non-receptive patients.

Conclusions

The rsERT can significantly improve the pregnancy outcomes of RIF patients, indicating the clinical potential of rsERT-guided pET.

Effects of Variable Embryo Transfer on the Variable Window of Implantation and Analysis of Pregnancy Outcomes

Background A descriptive analysis of patients who underwent various embryo transfer methods to address the root cause of their infertility at a tertiary infertility care complex in Wardha, India, is presented herein. This analysis aims to evaluate the management of infertility and assess pregnancy outcomes. Methodology We conducted a retrospective cohort study on patients who underwent various embryo transfer methods to address the cause of their infertility, specifically focusing on a variable window of implantation (WOI) at a tertiary infertility clinic over a one-year period. The medical records of 11 patients in both the variable embryo transfer (VET) and control groups were reviewed and analyzed for this article. Results The examination of medical records revealed a significant improvement in the rate of implantation (p-value = 0.04) and clinical pregnancy outcomes (p-value = 0.03) among patients who underwent VET. Comparable statistical outcomes were observed for other variables of pregnancy outcome, including miscarriage rate, multiple pregnancy rate, and biochemical pregnancy rate. Conclusion This retrospective cohort study suggests that the utilization of VET could be a viable option for women experiencing recurrent implantation failure cycles, particularly when an adequate number of embryos are available. This is owing to the challenges in clinically diagnosing a variable WOI. Further studies with a significantly larger sample population are recommended to validate the results and integrate this approach into the standard operating procedures, aiming to enhance the likelihood of pregnancy in these populations.

Luteal phase support in assisted reproductive technology

Infertility affects one in six couples, with in vitro fertilization (IVF) offering many the chance of conception. Compared to the solitary oocyte produced during the natural menstrual cycle, the supraphysiological ovarian stimulation needed to produce multiple oocytes during IVF results in a dysfunctional luteal phase that can be insufficient to support implantation and maintain pregnancy. Consequently, hormonal supplementation with luteal phase support, principally exogenous progesterone, is used to optimize pregnancy rates; however, luteal phase support remains largely 'black-box' with insufficient clarity regarding the optimal timing, dosing, route and duration of treatment. Herein, we review the evidence on luteal phase support and highlight remaining uncertainties and future research directions. Specifically, we outline the physiological luteal phase, which is regulated by progesterone from the corpus luteum, and evaluate how it is altered by the supraphysiological ovarian stimulation used during IVF. Additionally, we describe the effects of the hormonal triggers used to mature oocytes on the degree of luteal phase support required. We explain the histological transformation of the endometrium during the luteal phase and evaluate markers of endometrial receptivity that attempt to identify the 'window of implantation'. We also cover progesterone receptor signalling, circulating progesterone levels associated with implantation, and the pharmacokinetics of available progesterone formulations to inform the design of luteal phase support regimens.

When the Embryo Meets the Endometrium: Identifying the Features Required for Successful Embryo Implantation

Evaluation of the optimal number of embryos, their quality, and the precise timing for transfer are critical determinants in reproductive success, although still remaining one of the main challenges in assisted reproduction technologies (ART). Indeed, the success of in vitro fertilization (IVF) treatments relies on a multitude of events and factors involving both the endometrium and the embryo. Despite concerted efforts on both fronts, the overall success rates of IVF techniques continue to range between 25% and 30%. The role of the endometrium in implantation has been recently recognized, leading to the hypothesis that both the "soil" and the "seed" play a central role in a successful pregnancy. In this respect, identification of the molecular signature of endometrial receptivity together with the selection of the best embryo for transfer become crucial in ART. Currently, efforts have been made to develop accurate, predictive, and personalized tests to identify the window of implantation and the best quality embryo. However, the value of these tests is still debated, as conflicting results are reported in the literature. The purpose of this review is to summarize and critically report the available criteria to optimize the success of embryo transfer and to better understand current limitations and potential areas for improvement.

A Case Series Based on the Mixed Double-Embryo Transfer (MDET) Outcome in Patients With Recurrent Implantation Failure

Successful implantation of embryos depends on the synchronous cross-talks between the endometrial wall and the competent blastocyst within the window of implantation (WOI). Hence, the WOI has a major significance in assisted reproductive technology (ART). However, in some cases, women do not have fixed WOI in ART cycles in order to enhance the rate of successful clinical pregnancy. However, there have been stances where women do not have a fixed WOI, and it shifts in subsequent menstrual periods. This contributes to the chances of recurrent implantation failure (RIF). Another factor that contributes to RIF is erratic endometrial receptivity, which hinders the chances of successful implantation of the conceptus in the endometrium. This case series consists of four case studies where the patients were believed to be suffering from RIF due to variable WOI or erratic endometrial receptivity and the routine protocol followed nowadays failed to make them conceive. In order to resolve the condition, we proposed a novel strategy in an attempt to improve pregnancy rates in these cases. An innovative method of embryo transfer known as mixed double-embryo transfer (MDET), which involved the transfer of one day 3 embryo and one day 5 blastocyst on day 6 of progesterone, led to possible pregnancy outcomes. A viable pregnancy was validated based on the human chorionic gonadotropin (β-hCG) test report, and two of the cases delivered healthy babies. Thus, this case series provides a unique approach to addressing the issues of RIF. However, larger studies are required to validate the possible use of this technique.

Assessing the Impact of Genratest on Women With Recurrent Implantation Failure: A Single-Center Study

Objective Recurrent implantation failure (RIF) is a significant challenge in assisted reproduction. Genratest has emerged as a potential tool to identify the displaced window of implantation (WOI). This study aimed to evaluate the impact of this test on the pregnancy outcomes of RIF patients. Methods A retrospective analysis was conducted on 143 RIF patients who were categorized into two groups: the personalized embryo transfer (pET, n=69) group and standard embryo transfer (sET, n=74) group. The main measured outcomes were clinical pregnancy, ongoing pregnancy, miscarriage, and live birth rates. Results Genratest effectively diagnoses the displaced WOI in 90% of RIF patients. The pET group exhibited a higher rate of clinical pregnancy (n=36/69, 52.2%) compared to the sET group (n=35/74, 47.3%), but this difference was not statistically significant (p=0.679). Ongoing pregnancy rates were comparable between the pET (n=28/69, 40.6%) and the sET (n=30/74, 40.5%) groups (p=0.996). Live birth rates showed no statistically significant difference between the two groups (n=26/69, 37.7% versus n=22/74, 29.7%, p=0.407). Miscarriage rates were similar in both groups (n=9/69, 13% versus n=11/74, 14.9%, p=0.942). Conclusions pET based on the results of the Genratest did not show a significant improvement in pregnancy outcomes, including clinical pregnancy, ongoing pregnancy, live birth, or miscarriage rates. Further research is needed to identify the role of Genratest in RIF patients.

Effect of sequential embryo transfer on in vitro fertilization and embryo transfer outcomes: a systematic review and meta-analysis

Background

Sequential embryo transfer has been recognized as a strategy to increase pregnancy rates in women undergoing in vitro fertilization and embryo transfer (IVF-ET). However, its impact on assisted reproductive outcomes remains to be substantiated by robust evidence. This systematic review aims to summarize and analyze the available evidence to investigate the effect of sequential embryo transfer on assisted reproductive outcomes.

Methods

A comprehensive literature search was executed across the Pubmed, Cochrane Library, Web of Science, and Scopus databases in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Data were aggregated utilizing a random effects model, and the resultant outcomes were articulated as odds ratios (ORs) along with their 95% confidence intervals (CIs).

Results

The pooled results revealed a statistically significant enhancement in reproductive outcomes for infertile patients undergoing sequential embryo transfer as evidenced by elevated rates of chemical pregnancy (OR = 1.67, 95% CI = 1.23-2.27), clinical pregnancy (OR = 1.78, 95% CI = 1.43-2.21), and ongoing pregnancy (OR = 1.54, 95% CI = 1.03-2.31). Compared with cleavage-stage embryo transfer, sequential transfer yielded superior outcomes in terms of chemical pregnancy rate (OR = 2.08, 95% CI = 1.35-3.19) and clinical pregnancy rate (OR = 1.78, 95% CI = 1.37-2.31). Furthermore, among the repeated implantation failure (RIF) cohort, sequential embryo transfer surpassed blastocyst-stage transfer, delivering a heightened chemical pregnancy rate (OR = 1.66, 95% CI = 1.19-2.53) and clinical pregnancy rate (OR = 1.65, 95% CI = 1.19-2.27).

Conclusion

Our meta-analysis indicates that sequential transfer may enhance clinical pregnancy rate in a small subgroup of well-selected women. While promising, further evidence from prospective studies is needed.

Gene pathway analysis of the endometrium at the start of the window of implantation in women with unexplained infertility and unexplained recurrent pregnancy loss: is unexplained recurrent pregnancy loss a subset of unexplained infertility?

This study aims to understand differences/similarities in the genetic profile of the endometrium at the start of window of implantation (WOI) in women with unexplained infertility (UI) and unexplained recurrent pregnancy loss (uRPL). Differentially expressed genes (DEGs) from the endometrium were evaluated using gene expression array and pathway enrichment analysis was performed to analyse gene expression pathways involved in both conditions. We found 2,171 genes arranged in 117 pathways and 730 genes arranged in 33 pathways differentially expressed in endometrium of patients in UI and uRPL, respectively. Complement-coagulation cascades, morphine addiction pathway, and PI3K-Akt signalling pathway were predominantly differentially expressed in UI. Cancer pathways, NF-κB signalling pathway, and actin cytoskeleton regulation pathway showed significant changes in uRPL. Forty-eight percent of DEGs and 84% of differentially expressed pathways in uRPL were found in the endometrium of UI patients. Unexpected close association in gene expression pathways between UI and uRPL is observed supporting the hypothesis 'uRPL is a clinical subset of UI'. Yet 100% DEGs overlap wasn't found suggesting the endometrium has still some different gene expression patterns at start of WOI in UI and uRPL. Lastly, diagnostic tools may be developed for uRPL because more specific genes-pathways are involved compared with UI, which shows broader genetic expression profile.

Endometrial receptivity tests in reproduction: a SWOT analysis

Endometrial receptivity and its management in assisted reproduction is now a significant focus of research interest. Endometrial receptivity tests, which analyze different panels of gene expression, are usually offered in fertility clinics to determine the women's individual 'window of implantation', providing a personalized timing for embryo transfer. However, there are still no definite indications on whether its inclusion in the study of the infertile couple or the study of patients with repeated implantation failure is essential.

Kisspeptin: a potential therapeutic target in patients with unexplained infertility?

BACKGROUND

Kisspeptin has recently emerged as a key regulator of the reproductive axis in women. Kisspeptin, acting centrally via the kisspeptin receptor, stimulates the secretion of the gonadotrophin-releasing hormone (GnRH).

AIMS

To investigate serum kisspeptin levels in infertility patients for its clinical utilisation in management and understanding of the pathophysiology of infertility in a wide array of patients.

METHODS

This prospective case-control study analysis involved 92 primary infertile women with PCOS, diminished ovarian reserve (DOR), unexplained infertility (UEI), and male factor infertility between 20 and 42 years of age. Serum samples were collected between the second and fifth day of the menstrual cycle. The kisspeptin level was determined using a human kisspeptin ELISA kit according to the manufacturer's procedure.

RESULTS

The median value of serum kisspeptin in the PCOS infertility group was significantly higher than that in the UEI group (p = 0.011). There was a statistically significant (p = 0.015, r =  -0.182) negative weak correlation found between serum kisspeptin levels and age. The optimal cutoff value obtained to differentiate the UEI from others (PCOS infertility + DOR + male factor infertility) according to the serum kisspeptin level was 214.3 ng/L with a sensitivity of 55% and specificity of 80.9%.

CONCLUSIONS

Understanding the role of kisspeptin may lead to its use as a biomarker in infertility diagnosis in UEI patients and might guide the use of kisspeptin analogues in selected patients for infertility management.

Immunological and immunohistochemical features of endometrial implantation factor in healthy patients of late reproductive age

Аbstract. Relevance. The number of women of older reproductive age is steadily increasing, and repeated failures of Assisted Reproductive Technologies programs during the transfer of high-quality embryos indicate the possibility of disruption of embryo implantation processes associated with impaired receptivity and functionality of the endometrium. Morphological, immunological and immunohistochemical changes in the endometrium associated with age factor may be decisive for the formation of the «implantation window» and correction of these changes and may improve the outcomes of Assisted Reproductive Technologies for a cohort of patients of older reproductive age. The aim of the study - to expand the pathogenetic understanding of the violation of the implantation ability of the endometrium in healthy patients of older reproductive age. Materials and Methods. A prospective sample study of 46 patients (group 1), aged 38 to 45 years with an officially registered diagnosis of infertility lasting no more than 4 years, with a successful gynecological and obstetric history, who were about to have their first IVF attempt, was conducted. The patients were examined according to Order № 803n of the Ministry of Health of the Russian Federation. Additionally, the level of peripheral blood melatonin, the determination of progesterone, estrogen, HLA-DR (MHC II), CD56 (NK cells), CD138, leukemia inhibiting factor receptors in the endometrium were studied. Concentrations of IL-6, IL-10, TGFß, and VGEF were determined in the cervical secretion, with the calculation of the pro-inflammatory index, as the ratio of IL-6/IL-10 cu and the ratio of TGFß1/VEGF. Statistical data processing was performed using the Statistica 10.0 application software package (StatSoft, Inc., USA). Results and Discussion. In the group of healthy patients of older reproductive age, there is an imbalance of steroid receptors and secretory transformation of the endometrium against the background of relative hyperestrogenism, with a decrease in the reception of own hormones in the endometrium. A decrease in melatonin signals a disorder of pineal and pituitary control over ovarian cycling. There is a decrease in the expression of leukemia inhibiting factor. Signs of inactive chronic endometritis with an autoimmune component are monitored, confirmed by a pro-inflammatory cytokine balance. The predominance of fibrosis processes over angiogenesis processes is confirmed by an increase in the ratio of TGFß1/VEGF and highly resistant blood flow in the uterine arteries. Conclusion. Standard pre-gravidar preparation cannot compensate for all factors that violate the implantation potential of the endometrium in this cohort of patients and requires the development of new complex techniques that directly affect the diversity of all factors that ensure the natural extinction of reproductive potential in order to increase the effectiveness of Assisted Reproductive Technologies programs.

Comparing the effect of sequential embryo transfer versus double blastocyst embryo transfer on pregnancy outcomes in intracytoplasmic sperm injection (ICSI) cycles in patients with repeated implantation failure: A randomized controlled trial

OBJECTIVE

Recurrent implantation failure (RIF) is the main challenge in assisted reproductive technology (ART) practice. Sequential embryo transfer, in which both, cleavage-stage embryo on day 3 and blastocyst on day 5, are sequentially transferred in the same cycle, has been suggested for increasing embryo implantation in RIF patients. The aim of the present study was to compare the effect of sequential embryo transfer versus double blastocyst embryo transfer on pregnancy outcomes in intracytoplasmic sperm injection (ICSI)/frozen embryo transfer (FET) cycles in RIF patients.

MATERIALS AND METHODS

This prospective study was enrolled 224 RIF patients undergoing ICSI/FET cycles and randomly divided to sequential and control groups. In sequential group, embryo transfer was conducted on day 3 (cleavage stage) and day 5 (blastocyst stage). In control group, two top-quality blastocysts were transferred on day 5.

RESULTS

Two hundred and two couples accomplished the trial, and their data were analyzed. Results demonstrated that sequential embryo transfer on day 3 and day 5 compared to double blastocyst transfer on day 5 significantly increased implantation rate, clinical pregnancy rate and ongoing pregnancy rate in RIF patients (p-value = 0.0142, p-value = 0.0154, p-value = 0.0201, respectively). However, there were no significant differences in terms of chemical pregnancy rate, multiple pregnancy rate, miscarriage rate and ectopic pregnancy rate in the studied groups.

CONCLUSION

Sequential embryo transfer is associated with improved pregnancy outcomes in RIF patients. Further prospective studies with larger sample sizes are required to validate these results.

Cervical Secretion Methylation Is Associated with the Pregnancy Outcome of Frozen-Thawed Embryo Transfer

The causes of implantation failure remain a black box in reproductive medicine. The exact mechanism behind the regulation of endometrial receptivity is still unknown. Epigenetic modifications influence gene expression patterns and may alter the receptivity of human endometrium. Cervical secretions contain endometrial genetic material, which can be used as an indicator of the endometrial condition. This study evaluates the association between the cervical secretion gene methylation profile and pregnancy outcome in a frozen-thawed embryonic transfer (FET) cycle. Cervical secretions were collected from women who entered the FET cycle with a blastocyst transfer (36 pregnant and 36 non-pregnant women). The DNA methylation profiles of six candidate genes selected from the literature review were measured by quantitative methylation-specific PCR (qMSP). Bioinformatic analysis of six selected candidate genes showed significant differences in DNA methylation between receptive and pre-receptive endometrium. All candidate genes showed different degrees of correlation with the pregnancy outcomes in the logistic regression model. A machine learning approach showed that the combination of candidate genes' DNA methylation profiles could differentiate pregnant from non-pregnant samples with an accuracy as high as 86.67% and an AUC of 0.81. This study demonstrated the association between cervical secretion methylation profiles and pregnancy outcomes in an FET cycle and provides a basis for potential clinical application as a non-invasive method for implantation prediction.

Hypoxia-sensitive miRNA regulation via CRISPR/dCas9 loaded in hybrid exosomes: A novel strategy to improve embryo implantation and prevent placental insufficiency during pregnancy

Assisted reproductive techniques as a new regenerative medicine approach have significantly contributed to solving infertility problems that affect approximately 15% of couples worldwide. However, the success rate of an in vitro fertilization (IVF) cycle remains only about 20%-30%, and 75% of these losses are due to implantation failure (the crucial rate-limiting step of gestation). Implantation failure and abnormal placenta formation are mainly caused by defective adhesion, invasion, and angiogenesis. Placental insufficiency endangers both the mother's and the fetus's health. Therefore, we suggested a novel treatment strategy to improve endometrial receptivity and implantation success rate. In this strategy, regulating mir-30d expression as an upstream transcriptomic modifier of the embryo implantation results in modified expression of the involved genes in embryonic adhesion, invasion, and angiogenesis and consequently impedes implantation failure. For this purpose, "scaffold/matrix attachment regions (S/MARs)" are employed as non-viral episomal vectors, transfecting into trophoblasts by exosome-liposome hybrid carriers. These vectors comprise CRISPR/dCas9 with a guide RNA to exclusively induce miR-30d gene expression in hypoxic stress conditions. In order to avoid concerns about the fetus's genetic manipulation, our vector would be transfected specifically into the trophoblast layer of the blastocyst via binding to trophoblast Erb-B4 receptors without entering the inner cell mass. Additionally, S/MAR episomal vectors do not integrate with the original cell DNA. As an on/off regulatory switch, a hypoxia-sensitive promoter (HRE) is localized upstream of dCas9. The miR-30d expression increases before and during the implantation and placental insufficiency conditions and is extinguished after hypoxia elimination. This hypothesis emphasizes that improving the adhesion, invasion, and angiogenesis in the uterine microenvironment during pregnancy will result in increased implantation success and reduced placental insufficiency, as a new insight in translational medicine.

The effect of Nifedipine on embryo transfer outcomes: A randomized clinical trial

Background

Endometrial receptivity is crucial for embryo implantation, and excessive uterine contraction reduces success. Nifedipine which is a calcium channel blocker, could decrease uterine contraction and improve pregnancy outcomes.

Objective

This study aimed to assess the effect of Nifedipine before embryo transfer on the pregnancy outcome in women undergoing in vitro fertilization (IVF) in a tertiary center in Iran.

Materials and Methods

150 women who were candidates for IVF were randomly assigned into 2 groups: group 1 received 20 mg Nifedipine 30 min before embryo transfer, and group 2 received no intervention. Blood pressure of the participants was monitored every 10 min for 1 hr under the supervision of an anesthesiologist. Finally, implantation rate and chemical and clinical pregnancy rates were compared between groups.

Results

At the end of the study, 140 participants were included in the final analyses. No significant difference was observed in clinical pregnancy rates between groups (20% vs. 22%, p = 0.51).

Conclusion

Nifedipine administration before embryo transfer does not improve the implantation and clinical pregnancy rates in women undergoing IVF.

The challenges of obesity for fertility: A FIGO literature review

Obesity has been linked to infertility through several mechanisms, including at a molecular level. Those living with obesity face additional barriers to accessing fertility treatments and achieving a successful pregnancy, which can contribute to their economic and psychosocial stressors. There is scope to further improve care for people living with obesity and infertility with empathy, via a multidisciplinary approach.

Individual dynamics of uterine natural killer cells in natural and stimulated cycles monitored using a new endometrial dating method

PROBLEM

It is important to evaluate the dynamics of uterine natural killer (uNK) cells in hormone replacement therapy (HRT) cycles, given their potential role in implantation and the common usage of HRT cycles with in vitro fertilization (IVF).

METHOD OF STUDY

A total of 132 subfertile patients were evaluated during the secretory phase of either natural ovulation (OV) or HRT cycles, with two biopsies taken on approximately days 5 and 10 after ovulation/progesterone administration in a single menstrual cycle. Immunohistochemical Personal Endometrial Maturation Analysis (PEMA) was used to better quantify secretory-phase endometrial development, in combination with subsequent evaluation of uNK cell density.

RESULTS

uNK cell density increased rapidly from the early to mid-secretory phase, with mean uNK densities of 113 and 117 per mm² in first biopsies and 315 and 387 per mm² in second biopsies for OV and HRT cycles, respectively. After reassessment of endometrial development with PEMA, the first and second biopsies in HRT and OV cycles were histologically dated to developmental ranges between days 15-20 (first biopsy) and days 19-25 (second biopsy).

CONCLUSION

Subfertile women showed variable endometrial development in PEMA assessment, with uNK cell density correlating with the dating results. Overall, comparable levels of uNK cell density were observed in OV and HRT cycles. Importantly, uNK cell density depends on the histological maturation stage, with similar low coefficients of determination. This observation suggests that aberrant uNK cell results more likely reflect displaced endometrial maturation, rather than an intrinsic anomaly in uNK cell trafficking.

The role of timing in frozen embryo transfer

The process of implantation is characterized by a complex cross-talk between the endometrium and the blastocyst, with the endometrium only being receptive to implantation during a transient window of implantation of approximately 2-3 days during the midsecretory phase. The timing of embryo transfer, including frozen embryo transfer, is therefore critical to the success of implantation. In this article, we discuss various elements that may guide the timing of frozen embryo transfer, including the role of endometrial characteristics such as thickness, days postovulation or length of progesterone administration, stage of the embryo, and the application of endometrial receptivity tests to guide personalized embryo transfer.

Commercially Available Molecular Approaches to Evaluate Endometrial Receptivity: A Systematic Review and Critical Analysis of the Literature

Despite the advances in the field of reproductive medicine, implantation failure represents a challenging condition affecting 10-30% of patients subjected to in vitro fertilization (IVF). Research has focused on the identification of molecules playing crucial roles in endometrial receptivity, with the aim of designing predictive tools for efficient detection of the implantation window. To that end, novel molecular genomic and transcriptomic approaches have been introduced as promising tools to enable personalized approaches with the aim of optimizing embryo transfer dating. However, the clinical value of these approaches remains unclear. The aim of this study is to provide a systematic review and critical analysis of the existing evidence regarding the employment of commercially available novel approaches to evaluate endometrial receptivity. An Embase and PubMed/Medline search was performed on 1 February 2022. From the 475 articles yielded, only 27 were included and analyzed. The considerable heterogeneity of the included articles indicates the uniqueness of the implantation window, showcasing that the optimal time for embryo transfer varies significantly between women. Moreover, this study provides information regarding the technical aspects of these advanced molecular tools, as well as an analysis of novel possible biomarkers for endometrial receptivity, providing a basis for future research in the field.

Assessment of mitochondrial DNA viability ratio in day-4 biopsied embryos as an add-in to select euploid embryos for single embryo transfer

The aim of this study was to assess mitochondrial DNA analysis as a predictor of the pregnancy potential of biopsied preimplantation embryos. The study included 78 blastomeres biopsied from day 4 cleavage stage euploid embryos. The embryo karyotype was confirmed by 24-chromosome preimplantation genetic testing for aneuploidies using the Illumina Next-Generation Sequencing (NGS) system. Mitochondria viability ratios (mtV) were determined from BAM files subjected to the web-based genome-analysis tool Galaxy. From this cohort of patients, 30.4% of patients (n = 34) failed to establish pregnancy. The mean mtV ratio [mean = 1.51 ± 1.25-1.77 (95% CI)] for this group was significantly (P < 0.01) lower compared with the embryo population that resulted in established pregnancies [mean = 2.5 ± 1.82-2.68 (95% CI)]. mtV multiple of mean (MoM) values were similarly significantly (P < 0.01) lower in blastocysts failing to establish pregnancy. At a 0.5 MoM cut-off, the sensitivity of mtV quantitation was 35.3% and specificity was 78.2%. The positive predictive value for an mtV value > 0.5 MoM was 41.4%. This study demonstrates the clinical utility of preimplantation quantification of viable mitochondrial DNA in biopsied blastomeres as a prognosticator of pregnancy potential.

Advances in the clinical application of ultrasound elastography in uterine imaging

Changes in tissue stiffness by physiological or pathological factors in tissue structure are identified earlier than their clinical features. Pathological processes such as uterine fibrosis, adenomyosis, endometrial lesions, infertility, and premature birth can manifest as tissue elasticity changes. In clinical settings, elastography techniques based on ultrasonography, optical coherence tomography, and magnetic resonance imaging are widely used for noninvasive measurement of mechanical properties in patients, providing valuable tool and information for diagnosis and treatment. Ultrasound elastography (USE) plays a critical role in obstetrics and gynecology clinical work because of its simplicity, non-invasiveness, and repeatability. This article reviews the recent progress of USE in uterine tumor diagnosis (especially early diagnosis and treatment effect evaluation), prediction of preterm birth, and intrauterine insemination. We believe that USE, especially shear wave elastography, may serve as a potential means to assess tissue stiffness, thereby improving the diagnosis and treatment of adenomyosis, fibroids, endometrial lesions, cervical cancer, and precise management of preterm birth and intrauterine insemination monitoring.

Aberrant uterine folding in mice disrupts implantation chamber formation and alignment of embryo-uterine axes

The uterine luminal epithelium folds characteristically in mammals, including humans, horses and rodents. Improper uterine folding in horses results in pregnancy failure, but the precise function of folds remains unknown. Here, we uncover dynamic changes in the 3D uterine folding pattern during early pregnancy with the entire lumen forming pre-implantation transverse folds along the mesometrial-antimesometrial axis. Using a time course, we show that transverse folds are formed before embryo spacing, whereas implantation chambers form as the embryo begins attachment. Thus, folds and chambers are two distinct structures. Transverse folds resolve to form a flat implantation region, after which an embryo arrives at its center to attach and form the post-implantation chamber. Our data also suggest that the implantation chamber facilitates embryo rotation and its alignment along the uterine mesometrial-antimesometrial axis. Using WNT5A- and RBPJ-deficient mice that display aberrant folds, we show that embryos trapped in longitudinal folds display misalignment of the embryo-uterine axes, abnormal chamber formation and defective post-implantation morphogenesis. These mouse models with disrupted uterine folding provide an opportunity to understand uterine structure-based mechanisms that are crucial for implantation and pregnancy success.

This article has an associated ‘The people behind the papers’ interview.

Use of 'omics for endometrial timing: the cycle moves on

For some years, the prospect of precise and personalized timing of the endometrial cycle for optimal embryo replacement has been held out as a potential solution to low implantation rates. It is envisaged that a receptive state can be defined and reached at a predictable time, and embryo replacement performed in synchrony. In the last century, morphological changes characteristic of the mid secretory phase were defined in precisely timed cycles in women of proven fertility, but when deviations from this standardized schedule occur, their significance for implantation has remained uncertain. ‘Omics technologies have been widely advocated for staging the endometrial cycle and defining a set of biochemical requirements for implantation, but after two decades of research, improvements to pregnancy rates have not followed, and there is a striking lack of agreement regarding the molecular characterization of the receptive state. Some of the rationale underlying these problems is now emerging with the application of higher-level computational and biological methodology. Here, we consider the challenges of defining an endometrial phenotype that can support implantation and continuing pregnancy. Receptivity may be an emergent trait depending on contributions from multiple proteins that have low pathway connectivity. We recommend that authors choose language which rigorously avoids the implication that protocols for molecular staging of the mid secretory phase inherently identify a state of receptivity to the implanting blastocyst.

The risk of intrauterine exposure to SARS-CoV-2 in female COVID-19 patients: A comprehensive review

Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is a new type of coronavirus that has caused fatal infectious diseases and global spread. This novel coronavirus attacks target cells through the interaction of spike protein and angiotensin‐converting enzyme II (ACE2), leading to different clinical symptoms. However, for a successful pregnancy, a well‐established in‐uterine environment includes a specific immune environment, and multi‐interactions between specific cell types are prerequisites. The immune‐related changes in patients infected with novel coronavirus could interfere with the immune microenvironment in the uterus, leading to fetal loss. We first reviewed the intrauterine environment in the normal development process and the possible pregnancy outcome in the infection state. Then, we summarized the immune response induced by SARS‐CoV‐2 in patients and analyzed the changes in ACE2 expression in the female reproductive system. Finally, the present observational evidence of infection in pregnant women was also reviewed.

Assisted Hatching Treatment of Piezo-Mediated Small Hole on Zona Pellucida in Morula Stage Embryos Improves Embryo Implantation and Litter Size in Mice

For in vitro produced embryos generated from in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) procedure, the intra- and extra-environmental factors during in vitro culture have significant impact on latter embryo development and fetus growth. Assisted hatching (AH), an effective approach to facilitate hatchability for in vitro generated embryos, is an essential step for successful embryo implantation in the uterus. However, regarding the different AH methods reported in clinical practice, it is still unknown whether zona pellucida (ZP) broken is based on AH applied in diverse stages of embryos affect implantation and fetal development. Here, piezo-mediated AH treatments were classified into four categories: (1) drilling one small hole (SH) with a diameter of 10 μm on ZP (SH); (2) drilling one large hole (LH) with a diameter of 40 μm on ZP (LH); (3) made a small area with diameter of 40-μm thinner on ZP [small area thinner (ST)]; (4) made a large area with a diameter of 80-μm thinner [large area thinner (LT)]. These four AH treatments were applied in different stage embryos including two-cell, four-cell, and morula. The most efficient AH approach was chosen according to the final hatch rate at 120 h after fertilization. We found that the approach of SH applied in morula-stage embryos obtained the highest hatch rate. To further investigate if this treatment has any side effect on later development after embryo transfer, we evaluated embryo implantation, gestational period, litter size, and growth. Our results showed that SH applied in morula-stage embryos could facilitate the implantation process and increase litter size. Meanwhile, this approach had no side effect on birth weight, growth, or gender ratio in the offspring. We conclude that drilling a SH on ZP in morula-stage embryos is an effective and reliable AH approach for in vitro cultured embryos in rodent. And this approach is worth further investigating in human-assisted reproductive technology.