Association Between Endometrial/Subendometrial Vasculature and Embryo Transfer Outcome: A Meta-analysis and Subgroup Analysis

Vasodilators for women undergoing fertility treatment

BACKGROUND

The rate of successful pregnancies brought to term has barely increased since the first assisted reproductive technology (ART) technique became available. Research suggests that vasodilators may increase endometrial receptivity, thicken the endometrium, and favour uterine relaxation, all of which could improve the chances of successful assisted pregnancy.

OBJECTIVES

To evaluate the effectiveness and safety of vasodilators in women undergoing fertility treatment.

SEARCH METHODS

We searched the Cochrane Gynaecology and Fertility Group Specialised Register of controlled trials, CENTRAL, MEDLINE, Embase, three other databases, and two clinical trial registries in April 2024, with no language or date restrictions. We also searched grey literature sources and checked the reference lists of relevant articles.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing vasodilators (alone or combined with other treatments) versus placebo or no treatment or versus other agents in women undergoing fertility treatment.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies, assessed risk of bias, extracted data, and calculated risk ratios (RRs). We combined study data using a fixed-effect model and assessed evidence certainty using the GRADE approach. Our primary outcomes were live birth or ongoing pregnancy and vasodilator side effects. Our secondary outcomes were clinical pregnancy, endometrial thickness, multiple gestation, miscarriage, and ectopic pregnancy.

MAIN RESULTS

We included 45 studies with a total of 4404 women. The included studies compared a vasodilator versus a placebo or no treatment (40 RCTs), vasodilators plus another agent versus placebo or no treatment (3 RCTs) or versus oestrogens (3 RCTs). The mean length of follow-up was 15.45 weeks. Overall, the certainty of evidence was very low to moderate. The main limitations were imprecision (low number of events and participants) and risk of bias (lack of blinding in studies that reported subjective outcomes). Vasodilators versus placebo or no treatment Vasodilators may result in little to no difference in rates of live birth or ongoing pregnancy compared with placebo or no treatment (RR 1.21, 95% CI 0.93 to 1.58; I² = 0%; 6 RCTs, 740 women; low-certainty evidence), but probably increase overall rates of side effects (RR 2.14, 95% CI 1.55 to 2.98; I² = 0%; 7 RCTs, 668 women; moderate-certainty evidence). The evidence suggests that 246 per 1000 women achieve live birth or ongoing pregnancy with a placebo or no treatment, and 229 to 389 per 1000 will do so using vasodilators. Vasodilators compared with placebo or no treatment likely increase rates of clinical pregnancy (RR 1.45, 95% CI 1.28 to 1.64; I² = 22%; 25 RCTs, 2506 women; moderate-certainty evidence). Vasodilators compared with placebo or no treatment probably have little or no effect on rates of multiple gestation or birth (RR 1.37, 95% CI 0.73 to 2.55; I² = 0%; 7 RCTs, 763 women; moderate-certainty evidence), miscarriage (RR 1.01, 95% CI 0.59 to 1.74; I² = 0%; 8 RCTs; 829 women; moderate-certainty evidence), and ectopic pregnancy (RR 1.25, 95% CI 0.34 to 4.59; I² = 0%; 4 RCTs, 543 women; moderate-certainty evidence). Most studies found a beneficial effect of vasodilators for endometrial thickness, but the reported effect estimates varied (I² = 93%), from a mean difference of 0.47 mm higher (95% CI 0.90 mm lower to 1. 84 mm higher) to 1.94 mm higher (95% CI 1.37 higher to 2.51 mm higher), and the evidence was very uncertain. Hence, we are unsure how to interpret these results. Vasodilators versus oestrogens Vasodilators compared with oestrogens may have little or no effect on rates of live birth or ongoing pregnancy (RR 0.83, 95% CI 0.30 to 1.33; 1 RCT, 44 women, low-certainty evidence). The evidence is very uncertain regarding the effect of sildenafil compared with oestrogens on clinical pregnancy rates (RR 0.99, 95% CI 0.71 to 1.38; I² = 59%; 3 RCTs, 262 women; very low-certainty evidence), endometrial thickness (RR 1.90, 95 CI 1.15 to 3.13; 1 RCT, 120 women; very low-certainty evidence) and miscarriage rates (RR 0.50, 95% CI 0.05 to 5.12; 1 RCT, 44 women; very low-certainty evidence) AUTHORS' CONCLUSIONS: Among women undergoing fertility treatment, there may be little or no difference in the rate of live birth or ongoing pregnancy in those who receive vasodilators compared with those who receive a placebo or no treatment, and compared with those who receive oestrogens. Compared with placebo or no treatment, vasodilators likely increase rates of clinical pregnancy, but probably also increase overall rates of side effects. The evidence on clinical pregnancy with vasodilators versus oestrogens is very uncertain, and we found no evidence on overall side effects for the comparison of vasodilators versus oestrogens. We are unsure about the effect of vasodilators versus placebo or no treatment and versus oestrogens on endometrial thickness. Vasodilators versus placebo or no treatment probably have little or no effect on multiple gestation or birth, miscarriage, and ectopic pregnancy. Future studies should be adequately randomised and powered to ensure a more accurate evaluation of each treatment, with live births as a primary outcome.

Utilizing MV-FLOW™ and multidimensional ultrasound characteristics for prognosticating FET outcomes in RIF patients: Study Protocol for a cross-sectional study

Recurrent implantation failure (RIF) is a common issue in frozen-thawed embryo transfer (FET). Prior to transfer, uterine endometrial receptivity of FET patients can be assessed using multimodal transvaginal ultrasound indicators to predict the success rate of the current FET cycle. Endometrial blood flow is a crucial element in evaluating endometrial receptivity. MV-FLOW™ is an advanced two-dimensional superb microvascular imaging technology that can detect and display blood flow in micro-vessels. The data for this study were obtained from an ongoing cross-sectional study comprising 323 RIF patients and 323 first implantation (FI) patients, who underwent transvaginal ultrasound before FET. We collected basic clinical data and multimodal ultrasound data from these patients as predictive features, with clinical pregnancy as the predictive label, for model training. Based on the above, this study aims to establish and validate a clinical prediction model for FET outcomes using support vector classification (SVC) algorithms, based on MV-FLOW™ and multidimensional transvaginal ultrasound imaging features. The objective is to determine the predictive role of multimodal transvaginal ultrasound in embryo transfer outcomes and provide evidence for the clinical application of MV-FLOW™. Trial registration: Trial Registration: ChiCTR2400086401.

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.

Subendometrial blood flow detected by Doppler ultrasound associates with pregnancy outcomes of frozen embryo transfer in patients with thin endometrium

PURPOSE

Multiple factors have been shown to influence the rate of clinical pregnancy after FET in IVF treatment, including embryo quality, synchronization of embryo and endometrium, and endometrial receptivity (ER). The subendometrial blood flow conditions could also contribute potentially major effects toward the establishment and maintenance of pregnancy. We conducted a retrospective cohort study to examine the correlation between subendometrial blood flow, as determined by Doppler ultrasound, and pregnancy outcomes in IVF patients with a thin endometrium (endometrium thickness [EMT] ≤ 0.7 cm).

METHODS

This was a retrospective cohort study conducted at a university-affiliated reproductive hospital from January 2017 to April 2023. The EMT and subendometrial blood flows were assessed using transvaginal color Doppler ultrasound and evaluated by experienced clinical ultrasound physicians on the endometrial transformation day. The pregnancy outcomes were followed up and documented in clinical medical records through the IVF cohort study at our center.

RESULTS

In the patients with 0.5 cm ≤ EMT ≤ 0.7 cm, the embryo implantation rate was statistically significant increased in the patients with the presence of subendometrial blood flow (OR 1.484; 95% CI, 1.001-2.200; P = 0.049; aOR 1.425; 95% CI, 1.030-2.123; P = 0.003). Patients with discernible subendometrial blood flow have superior live birth (P = 0.028), clinical pregnancy (P = 0.049), and embryo implantation (P = 0.027) compared to the patients without subendometrial blood flow when the EMT is ≤ 0.7 cm.

CONCLUSIONS

The presence of subendometrial blood flow detected by ultrasound was positively associated with successful embryo implantation and favorable pregnancy outcomes in patients with thin endometrium undergoing FET.

Enhancing endometrial receptivity in FET cycles: exploring the influence of endometrial and subendometrial blood flow along with endometrial volume

Introduction

Fetal health and a receptive and healthy endometrium are two essential factors in achieving successful implantation. If the endometrium is unreceptive, postponing the transfer cycle to a suitable time can enhance the chances of pregnancy. This study aims to assess the impact of endometrial and sub-endometrial blood flows measured by Doppler ultrasound, as well as endometrial volume, on endometrial receptivity in frozen embryo transfer (FET) cycles.

Methods

112 patients with a mean age of 33.93 ± 4.93 years underwent in vitro fertilization (IVF). Serum β-hCG level was used to confirm pregnancy, and among the participants, 50 (44.6%) achieved pregnancy after IVF.

Results

The study results revealed a significant difference in endometrial blood flow between the pregnant and non-pregnant groups, with a higher pregnancy rate observed in participants exhibiting multi-focal and spare endometrial blood flows (p < 0.05). Furthermore, there was a notable association between endometrial blood flow and pregnancy outcome, as indicated by higher ongoing pregnancy rates in those with multi-focal and spare endometrial blood flows (p < 0.05). However, no significant differences were observed in endometrial variables such as volume, length, width, thickness, and pattern between the pregnant and non-pregnant groups. Additionally, contextual parameters showed no significant relationship with pregnancy outcome (p > 0.05). The study also found that endometrial measurement indices did not have a significant impact on pregnancy outcomes, with no significant differences observed between the groups (p > 0.05).

Conclusion

In conclusion, endometrial blood flow is crucial for a successful pregnancy after IVF, while the predictive value of the endometrial volume is limited for pregnancy outcomes.

The use of real time strain endometrial elastosonography plus endometrial thickness and vascularization flow index to predict endometrial receptivity in IVF treatments: a pilot study

BACKGROUND

The usefulness of endometrium strain elastosonography (SE) for the evaluation of endometrial receptivity in women undergoing in vitro fertilization (IVF) remains controversial. The objective of this prospective, observational study was to evaluate the correlation between endometrial thickness (EMT) and its related strain (ESR) on the day of ovulation triggering (hCG-d) and in vitro fertilization outcomes. Additionally, 3D Power Doppler vascular indices (3DPDVI) were also analysed.

METHODS

We included all the patients undergoing fresh IVF-single blastocyst transfer cycle from January 2021 to August 2021 at our center. On hCG-d, after B-mode scanning was completed to measure the EMT, the mode was changed to elastosonography to evaluate the ESR (ratio between endometrial tissue and the myometrium below). At the end of examination, the Endometrial Volume (EV) and 3DPDVI (vascularization index [VI], flow index [FI] and vascularization flow index [VFI]), were assessed. Statistical analysis was completed using STATA MP16 software.

RESULTS

A total number of 57 women were included. Based on the EMT on hCG-d, women were divided into two groups, Group 1: <7 mm and Group 2 ≥ 7 mm. Women with EMT < 7 mm had a significantly higher ESR (p = 0.004) and lower pregnancy rate (p = 0.04). Additionally, low ESR values were correlated with high VFI values (rho = -0.8; 95% CI = -0.9- -0.6; p < 0.0001) and EMT ≥ 7 mm could be predicted by low ESR (OR = 0.01; 95% CI = 0.01-0.30; p = 0.008, area under the ROC curve: 0.70). After all, in multiple logistic regression analysis, low values of ESR (p = 0.050) and high values of EMT (p = 0.051) on hCG-d had borderline statistical effects on pregnancy rate.

CONCLUSIONS

The ESR may be useful to improve the ultrasound evaluation of the endometrial quality in infertile women candidates to IVF/ICS. Given the small sample size of our study, the usefulness of strain elastosonography in this patients, needs further investigation.

Ultrasound‑assessed endometrial receptivity measures for the prediction of in vitro fertilization‑embryo transfer clinical pregnancy outcomes: A meta‑analysis and systematic review

At present, there are currently no reliable and consistent conclusions regarding transvaginal ultrasound assessment of endometrial receptivity in predicting clinical pregnancy outcomes of in vitro fertilization-embryo transfer (IVF-ET). Thus, in the present study, a meta-analysis was performed on multiple endometrial receptivity indices detected by vaginal ultrasound, aiming to provide a diagnostic basis for clinical practice. PubMed, Embase, and Cochrane Library databases were searched for studies published between the establishment of the databases through to January 2023. Studies that reported infertile women undergoing IVF-ET and undergoing vaginal ultrasound were included, but repeat publication, studies where the full text was not obtainable, studies where there was incomplete information provided or data extraction was not possible, studies on animals, case reports, reviews, and systematic reviews were excluded. STATA 15.1 was used to analyze the data. The pooled results showed that the endometrial thickness [Weighted mean difference (WMD)=0.03, 95% CI: 0.00-0.06; P=0.022] and endometrial volume (WMD=0.41, 95% CI: 0.07-0.74; P=0.017) of the pregnancy group after receiving IVF-ET were all significantly higher than that of the non-pregnancy group. The pooled results also showed that the vascularization index (VI) (WMD=0.79, 95% CI: 0.56-1.03; P=0.000), flow index (FI) (WMD=1.82, 95% CI: 0.83-2.81; P=0.000) and vascularization flow index (VFI) (WMD=1.58, 95% CI: 0.91-2.24; P=0.000) of the pregnancy group after receiving IVF-ET was significantly higher than that of the non-pregnancy group. Systolic/diastolic (S/D) (WMD=-4.92, 95%CI: -8.28- -1.56; P=0.004) of the uterine artery of the pregnancy group after receiving IVF-ET was significantly lower than that of the non-pregnancy group. However, the differences between the resistance index (RI) and pulsatility index (PI) in the pregnancy group vs. the non-pregnancy group after receiving IVF-ET were not statistically significant. Vaginal ultrasound can be used to predict the outcomes of pregnancy in infertile women undergoing IVF-ET by measuring the thickness and volume of the endometrium, combined with the S/D, VI, FI, and VFI of the uterine artery.

An ultrasound-based deep learning radiomic model combined with clinical data to predict clinical pregnancy after frozen embryo transfer: a pilot cohort study

RESEARCH QUESTION

Can a multi-modal fusion model based on ultrasound-based deep learning radiomics combined with clinical parameters provide personalized evaluation of endometrial receptivity and predict the occurrence of clinical pregnancy after frozen embryo transfer (FET)?

DESIGN

Prospective cohort study of women (n = 326) who underwent FET between August 2019 and December 2021. Input quantitative variables and input image data for radiomic feature extraction were collected to establish a multi-modal fusion prediction model. An additional independent dataset of 453 ultrasound endometrial images was used to establish the segmentation model to determine the endometrial region on ultrasound images for analysis. The performance of different algorithms and different input data for prediction of FET outcome were compared.

RESULTS

A total of 240 patients with complete data were included in the final cohort. The proposed multi-modal fusion model performed significantly better than the use of either image or quantitative variables alone to predict the occurrence of clinical pregnancy after FET (P ≤ 0.034). Its area under the curve, accuracy, sensitivity, specificity, positive predictive value and negative predictive value of the proposed model were 0.825, 72.5%, 96.2%, 58.3%, 72.3% and 89.5%, respectively. The Dice coefficient of the multi-task endometrial ultrasound segmentation model was 0.89. Use of endometrial segmentation features significantly improved the prediction performance of the model (P = 0.041).

CONCLUSIONS

The multi-modal fusion model based on ultrasound-based deep learning radiomics combined with clinical quantitative variables offers a favourable and rapid non-invasive approach for personalized prediction of FET outcome.

Association between endometrial blood and clinical outcome in frozen single blastocyst transfer cycles

Background: The success of embryo transfer cycle depends mainly on the quality of embryo and endometrial receptivity. Ultrasound examination is still the most widely used non-invasive evaluation method for its advantages of convenience, non-invasiveness and repeatability. Ultrasound-measured endometrial blood flow is one of the important evaluation indicators of morphology. Aims: To investigate the effect of the number of endometrial blood flow branches on pregnancy outcome of frozen-thawed embryo transfer cycles which have undergoing hormone replacement therapy (HRT-FET). Material and methods: A retrospective cohort study was performed looking at a total of 1390 HRT-FET cycles from our reproductive medicine center between January 2017 to December 2021, which transferred one blastocyst frozen on day 5 with good quality in morphology. Associations between endometrial blood flow branches and pregnancy outcomes were evaluated with multivariable linear regression analysis. Results: The number of endometrial blood flow branches was independently associated with clinical pregnancy (OR 1.10; 95% CI 1.02-1.20). After adjusting for potential confounders, the effect size (odds ratio) was 1.09 (95% CI 1.00-1.19), and the results showed that the clinical pregnancy rate and live birth rate of T2 and T3 groups were significantly higher than those in group T1 (p < 0.05). Subgroup analysis showed that a consistent association between the endometrial blood flow branches and clinical pregnancy in all subgroups. Conclusion: Our study provided evidence for the influence of endometrial blood flow on pregnancy outcomes. There may be an independent association between the number of endometrial blood flow branches and pregnancy outcomes in frozen-thawed single blastocyst transfer cycles.

Effects of sequential cleavage and blastocyst embryo transfer on pregnancy outcomes in patients with poor ovarian response

The management of patients with poor ovarian response (POR) remains a major challenge for fertility specialists in in vitro fertilization-embryo transfer (IVF-ET). In this retrospective cohort study, we aimed to evaluate the clinical effect of sequential transfer on pregnancy outcomes in patients with POR. A total of 3579 POR patients who underwent the first frozen embryo transfer (FET) cycle were enrolled from January 2018 to April 2021. The patients were divided into three groups according to the embryo transfer (ET) strategy adopted: a study group that included POR patients in whom a cleavage-stage embryo (day 3) and a blastocyst (day 5/6) were transferred (sequential transfer group), and two control groups in whom two cleavage-stage embryos (D3-dET group) or two blastocysts (D5/6-dET group) were transferred. The study group was matched with the control groups at a ratio of 1:4 by propensity score matching (PSM). The main pregnancy outcomes measured were the live birth rate and multiple pregnancy rate. After PSM, the live birth rate in the sequential transfer group was significantly higher than that in the D3-dET group (44.2% vs. 34.3%, P = 0.019), and was similar to that in the D5/6-dET group (44.2% vs. 45.3%; P = 0.90). In addition, there was no increase in the risk of multiple pregnancy among POR patients undergoing sequential transfer compared with both D3-dET (26.7% vs. 25.6%, P = 0.85) and D5/6-dET (26.7% vs. 28.4%, P = 0.97) groups. These findings imply that sequential transfer is an effective option for POR patients and could be utilized after careful consideration.

Inspection depth of uterine lumen measured by transvaginal ultrasound is associated with the success of IVF: a prospective longitudinal cohort study in China

OBJECTIVE

To measure the inspection depth of uterine lumen by transvaginal ultrasound and assess the association between the inspection depth and pregnancy outcomes in IVF-ET.

METHODS

This prospective longitudinal cohort study was conducted from June 2018 to December 2020. We enrolled patients aged 20-45 years who underwent frozen embryo transfer cycle. We calculated the average distance from the uterine lumen to the ultrasound probe (inspection depth) using transvaginal ultrasonography and divided the entire cohort into four groups according to the quartiles of the overall inspection depth distribution. The chi-square test was used to compare the pregnancy outcomes of the four groups. Univariate and multivariate regression analyses were performed to assess the association between the inspection depth and pregnancy outcomes.

RESULTS

Seven hundred forty-two patients were finally enrolled, and they were grouped according to the inspection depth quartiles. There were significant decrease in the clinical pregnancy, implantation, and live birth rates among the four groups (P < 0.05); however, there was no significant difference in the miscarriage rate. Multivariable logistic regression analysis with the inspection depth as a continuous variable demonstrated that the inspection depth was associated with clinical pregnancy, implantation, and live birth rates (clinical pregnancy rate, adjusted odds ratio, 0.549; 95% confidence interval, 0.380-0.793; implantation rate, adjusted odds ratio, 0.680; 95% confidence interval, 0.496-0.931; live birth rate, adjusted odds ratio, 0.602; 95% confidence interval, 0.420-0.863), but not with the miscarriage rate.

CONCLUSIONS

The inspection depth of the uterine lumen measured by transvaginal ultrasound was associated with IVF success.

TRIAL REGISTRATION

This prospective observational study was registered at the Chinese Clinical Trial Registry ( www.chictr.org.cn ) (ChiCTR2200057977) on March 24, 2022, retrospectively registered.

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.

Evidence and consensus on technical aspects of embryo transfer

BACKGROUND

Ultrasound-guided embryo transfer (US-GET) is a widely performed procedure, but standards for the best practice are not available.

OBJECTIVE AND RATIONALE

This document aims to provide an overview of technical aspects of US-GET after considering the published data and including the preparation for the embryo transfer (ET) procedure, the actual procedure, the post-procedure care, associated pathologies, complications and risks, quality assurance and practitioners’ performance.

SEARCH METHODS

A literature search for evidence on key aspects of the ET procedure was carried out from database inception to November 2021. Selected papers (n = 359) relevant to the topic were analysed by the authors. The following key points were considered in the papers: whether ultrasound (US) practice standards were explained, to what extent the ET technique was described and whether complications or incidents and how to prevent such events were reported. In the end, 89 papers could be used to support the recommendations in this document, which focused on transabdominal US-GET.

OUTCOMES

The relevant papers found in the literature search were included in the current document and described according to the topic in three main sections: requirements and preparations prior to ET, the ET procedure, and training and competence for ET. Recommendations are provided on preparations prior to ET, equipment and materials, ET technique, possible risks and complications, training and competence. Specific aspects of the laboratory procedures are covered, in particular the different loading techniques and their potential impact on the final outcomes. Potential future developments and research priorities regarding the ET technique are also outlined.

LIMITATIONS, REASONS FOR CAUTION

Many topics were not covered in the literature review and some recommendations were based on expert opinions and are not necessarily evidence based.

WIDER IMPLICATIONS

ET is the last procedural step in an ART treatment and is a crucial step toward achieving a pregnancy and live birth. The current paper set out to bring together the recent developments considering all aspects of ET, especially emphasizing US quality imaging. There are still many questions needing answers, and these can be subject of future research.

STUDY FUNDING/COMPETING INTEREST(S)

No funding. ADA has received royalties from CRC Press and personal honorarium from Cook, Ferring and Cooper Surgical. The other co-authors have no conflicts of interest to declare that are relevant to the content of this article.

Nomogram prediction for the prediction of clinical pregnancy in Freeze-thawed Embryo Transfer

BACKGROUND

This study aimed to identify multiple endometrial receptivity related factors by applying non-invasive, repeatable multimodal ultrasound methods. Combined with basic clinical data, we further established a practical prediction model for early clinical outcomes in Freeze-thawed Embryo Transfer (FET).

METHODS

Retrospective analysis of clinical data of infertility patients undergoing FET cycle in our Center from January 2017 to September 2019. Receiver operating characteristic (ROC) curve and decision curve analyses were performed by 500 bootstrap resamplings to assess the determination and clinical value of the nomogram, respectively.

RESULTS

A total of 2457 FET cycles were included. We developed simple nomograms that predict the early clinical outcomes in FET cycles by using the parameters of age, BMI, type and number of embryos transferred, endometrial thickness, FI, RI, PI and number of endometrial and sub-endometrial blood flow. In the training cohort, the area under the ROC curve (AUC) showed statistical accuracy (AUC = 0.698), and similar results were shown in the subsequent validation cohort (AUC = 0.699). Decision curve analysis demonstrated the clinical value of this nomogram.

CONCLUSIONS

Our nomogram can predict clinical outcomes and it can be used as a simple, affordable and widely implementable tool to provide guidance and treatment recommendations for FET patients.

An endometrial receptivity scoring system basing on the endometrial thickness, volume, echo, peristalsis, and blood flow evaluated by ultrasonography

BACKGROUND

Establishing a successful pregnancy depends on the endometrium and the embryo. It is estimated that suboptimal endometrial receptivity account for one-third of implantation failures. Despite the indepth understanding of the processes associated with embryo-endometrial cross-talk, little progress has been achieved for diagnosis and treatments for suboptimal endometrial receptivity.

METHODS

This retrospective study included women undergoing their first frozen-thawed embryo transfer (FET) cycles at our reproductive medicine center from March 2021 to August 2021. Transvaginal three-dimensional (3D) ultrasound was performed in the morning on the day of embryo transfer for all the thawed embryo transfer patients, to evaluate endometrial receptivity, including endometrial thickness, echogenicity, volume, movement and blood flow.

RESULTS

A total number of 562 patients of FET with 315 pregnancies (56.0%) was analyzed. It was found that only the echo of the endometrial central line was different between the pregnant group and non-pregnant group. Other parameters, such as endometrial thickness, volume, endometrial peristalsis, or the endometrial blood flow were not statistically different between the two groups. Then, according to the relationship between the different groups and the clinical pregnancy rate, a score of 0 to 2 was respectively scored. The sum of the scores for the six items was the patient's endometrial receptivity score. It showed that the clinical pregnancy rate increased as the endometrial receptivity score increased, and when the receptivity score reaches at least 5, the clinical pregnancy rate is significantly improved (63.7% versus 49.5%, P=0.001).

CONCLUSION

We developed an endometrial receptivity scoring system and demonstrated its validity. It may aid clinicians in choosing the useful marker in clinical practice and for informing further research.

Evaluating the role of endometrial colour Doppler dynamic tissue perfusion measurements in in vitro fertilisation success

The role of uterine receptivity and endometrial perfusion in in vitro fertilisation (IVF) remains unclear. In our prospective pilot study, we used a new dynamic tissue perfusion measurement method to evaluate this relationship in humans. A standard ovulation induction and embryo transfer method were applied to all the volunteers. On the day of embryo transfer, dynamic images of the uterus were recorded using colour Doppler ultrasound, and these images were uploaded onto PixelFlux Chameleon Software (GmbH, Münster, Germany). After determining the region of interest (ROI), the average velocity, intensity, and area values for all coloured pixels in the ROI, the tissue resistance index (RI) and the tissue pulsatility index were calculated. Endometrial thickness, morphology and dynamic endometrial perfusion parameters were compared between the clinically pregnant and non-pregnant groups. Endometrial thickness, morphology values and endometrial dynamic tissue perfusion measurements were similar between the groups. This study compared perfusion parameters between clinically pregnant and non-pregnant patients by accurately calculating endometrial tissue perfusion using standard software to establish its relationship with implantation success in IVF treatment.IMPACT STATEMENTWhat is already known about this subject? The relationship between IVF success, endometrial receptivity and perfusion is known. Clear valuations of endometrial receptivity require an endometrial biopsy which may cause endometrial damage to the actual IVF cycle. This problem has led researchers to conduct non-interventional studies. Studies have revealed the value of endometrial thickness, pattern and Doppler examination of endometrial uterine arteries in predicting the success of IVF treatment.What do the results of this study add? This prospective pilot study is the first one to use this programme in humans to evaluate uterine receptivity in IVF. Successful results can be obtained by using computer programmes in tissues where perfusion parameters cannot be measured using traditional colour Doppler ultrasonography. Revealing the relationship between tissue perfusion and IVF success will be more effective and accurate with the development of software technologies.What are the implications of these findings for clinical practice and/or further research? To increase the success of IVF treatment, current and new technological developments, as well as imaging methods should continue to be tested.

Sequential cleavage and blastocyst embryo transfer and IVF outcomes: a systematic review

BACKGROUND

Sequential embryo transfer has been proposed as a way to improve embryo implantation in women for in vitro fertilization (IVF), but the effect on pregnancy outcomes remains ambiguous. This systematic review was conducted to investigate the efficacy of sequential embryo transfer on IVF outcomes.

METHODS

A literature search was performed in the PubMed, Web of Science, Cochrane Library, ScienceDirect and Wanfang databases. Data were pooled using a random- or fixed-effects model according to study heterogeneity. The results are expressed as relative risks (RRs) with 95% confidence intervals (CIs). Heterogeneity was evaluated by the I² statistic. The study protocol was registered prospectively on INPLASY, ID: INPLASY202180019.

RESULTS

Ten eligible studies with 2658 participants compared sequential embryo transfer and cleavage transfer, while four studies with 513 participants compared sequential embryo transfer and blastocyst transfer. The synthesis results showed that the clinical pregnancy rate was higher in the sequential embryo transfer group than in the cleavage embryo transfer group (RR 1.42, 95% CI 1.26-1.60, P< 0.01) for both women who did experience repeated implantation failure (RIF) (RR 1.58, 95% CI 1.17-2.13, P< 0.01) and did not experience RIF (Non-RIF) (RR 1.44, 95% CI 1.20-1.66, P< 0.01). However, sequential embryo transfer showed no significant benefit over blastocyst embryo transfer.

CONCLUSION

The current systematic review demonstrates that sequential cleavage and blastocyst embryo transfer improve the clinical pregnancy rate over conventional cleavage embryo transfer. For women with adequate embryos, sequential transfer could be attempted following careful consideration. More high-grade evidence from prospective randomized studies is warranted.

The mechanism of action of oxytocin antagonist nolasiban in ART in healthy female volunteers

RESEARCH QUESTION

What are the effects of the oxytocin receptor (OTR) antagonist nolasiban on uterine contractions, endometrial perfusion and endometrial mRNA expression?

DESIGN

Randomized, double-blind, parallel-group, mechanism-of-action study with nolasiban. Forty-five healthy, pre-menopausal women were treated with placebo, 900 mg or 1800 mg nolasiban on the day corresponding to blastocyst transfer. Ultrasonographic uterine contraction frequency and endometrial perfusion were assessed, and endometrial biopsies analysed by next-generation sequencing.

RESULTS

Both doses of nolasiban showed decreased contraction frequency and increased endometrial perfusion depending on the time point assessed. At 1800 mg, 10 endometrial genes (DPP4, CNTNAP3, CNTN4, CXCL12, TNXB, CTSE, OLFM4, KRT5, KRT6A, IDO2) were significantly differentially expressed (adjusted P < 0.05). Of these, OLFM4, DPP4 and CXCL12 were regulated in the same direction as genes involved in implantation during the window of implantation. In addition, three genes (DPP4, CXCL12 and IDO2) were associated with decidualization and endometrial receptivity.

CONCLUSIONS

These data expand our knowledge of the mechanism of action of nolasiban in increasing pregnancy rates after embryo transfer. The results suggest more marked effects of nolasiban 1800 mg compared with the 900 mg dose, supporting testing at higher doses in IVF patients.

[Endometrial receptivity in assisted reproductive techniques: An aspect to investigate in embryo implantation failure]

Infertility affects between 8 and 12% of reproductive-age couples worldwide. Despite improvements in assisted reproductive techniques (ART), live birth rates are still limited. In clinical practice, imaging and microscopy are currently widely used, but their diagnostic effectiveness remains limited. In research, the emergence of innovative techniques named OMICS would improve the identification of the implantation window, while progressing in the understanding of the pathophysiological mechanisms involved in embryo implantation failures. To date, transcriptomic analysis seems to be the most promising approach in clinical research. The objective of this review is to present the results obtained with the different approaches available in clinical practice and in research to assess endometrial receptivity in patients undergoing ART.

Conventional and modern markers of endometrial receptivity: a systematic review and meta-analysis

BACKGROUND

Early reproductive failure is the most common complication of pregnancy with only 30% of conceptions reaching live birth. Establishing a successful pregnancy depends upon implantation, a complex process involving interactions between the endometrium and the blastocyst. It is estimated that embryos account for one-third of implantation failures, while suboptimal endometrial receptivity and altered embryo-endometrial dialogue are responsible for the remaining two-thirds. Endometrial receptivity has been the focus of extensive research for over 80 years, leading to an indepth understanding of the processes associated with embryo-endometrial cross-talk and implantation. However, little progress has been achieved to translate this understanding into clinically meaningful prognostic tests and treatments for suboptimal endometrial receptivity.

OBJECTIVE AND RATIONALE

The objective of this systematic review was to examine the evidence from observational studies supporting the use of endometrial receptivity markers as prognostic factors for pregnancy outcome in women wishing to conceive, in order to aid clinicians in choosing the most useful marker in clinical practice and for informing further research.

SEARCH METHODS

The review protocol was registered with PROSPERO (CRD42017077891). MEDLINE and Embase were searched for observational studies published from inception until 26 February 2018. We included studies that measured potential markers of endometrial receptivity prior to pregnancy attempts and reported the subsequent pregnancy outcomes. We performed association and accuracy analyses using clinical pregnancy as an outcome to reflect the presence of receptive endometrium. The Newcastle-Ottawa scale for observational studies was employed to assess the quality of the included studies.

OUTCOMES

We included 163 studies (88 834 women) of moderate overall quality in the narrative synthesis, out of which 96 were included in the meta-analyses. Studies reported on various endometrial receptivity markers evaluated by ultrasound, endometrial biopsy, endometrial fluid aspirate and hysteroscopy in the context of natural conception, IUI and IVF. Associations were identified between clinical pregnancy and various endometrial receptivity markers (endometrial thickness, endometrial pattern, Doppler indices, endometrial wave-like activity and various molecules); however, their poor ability to predict clinical pregnancy prevents them from being used in clinical practice. Results from several modern molecular tests are promising and further data are awaited.

WIDER IMPLICATIONS

The post-test probabilities from our analyses may be used in clinical practice to manage couples' expectations during fertility treatments (IUI and IVF). Conventionally, endometrial receptivity is seen as a dichotomous outcome (present or absent), but we propose that various levels of endometrial receptivity exist within the window of implantation. For instance, different transcriptomic signatures could represent varying levels of endometrial receptivity, which can be linked to different pregnancy outcomes. Many studies reported the means of a particular biomarker in those who achieved a pregnancy compared with those who did not. However, extreme values of a biomarker (as opposite to the means) may have significant prognostic and diagnostic implications that are not captured in the means. Therefore, we suggest reporting the outcomes by categories of biomarker levels rather than reporting means of biomarker levels within clinical outcome groups.

The Effect of Vaginal Sildenafil on The Outcome of Assisted Reproductive Technology Cycles in Patients with Repeated Implantation Failures: A Randomized Placebo-Controlled Trial

Background

The aim of this study was to investigate the effects of vaginal sildenafil on the outcome of patients with at least two unsuccessful in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) attempts.

Materials and Methods

In this randomized placebo-controlled trial study, a total of 66 infertile women aged ≤38 years, with a history of normal ovarian reserve, two prior consecutive failed IVF/ICSI attempts, human chorionic gonadotropin (hCG) day endometrial thickness <7 mm in all prior IVF/ICSI cycles, normal endometrial appear- ance by either hysteroscopy, hysterosonography, or hysterosalpingography enrolled in this study. The conventional gonadotropin-releasing hormone (GnRH) protocol was used for ovarian stimulation. The patients were randomly divided into three groups: vaginal sildenafil (suppository-100 mg/daily), vaginal placebo/sildenafil (suppository-100 mg/daily), and vaginal placebo (suppository). Each patient underwent colour Doppler ultrasound on day 14 of their previous cycle to investigate any abnormalities in the uterus and adnexa. Endometrial thickness, echo pattern, uterine artery resistance, and pulsatility indices were recorded pre- and post-treatment. The primary outcome measures were implantation, chemical and clinical pregnancy rates. For data analysis, SPSS version 20 software was used. In all tests, the significance level was considered less than 0.05.

Results

There was no significant difference between three groups in endometrial thickness on the hCG injection day. The chemical pregnancy in women who received sildenafil (alone or in combination with placebo) showed a two-fold increase in comparison to the placebo group. This increase was clinically meaningful, but according to sample size, it was statistically non-significant. The results of our study showed that the implantation was higher in women who received placebo/sildenafil compared to the other groups. The abortion rate was not statistically significant among the groups.

Conclusion

Vaginal sildenafil may conceivably improve chemical pregnancy rates in repeated IVF failure patients. Further randomized clinical trials using oral or vaginal sildenafil with higher sample size are recommended (Registra- tion number: NCT03192709).

Comparison of endometrial receptivity of clomiphene citrate versus letrozole in women with polycystic ovary syndrome: a randomized controlled study

The aim of the study was to compare the effect of clomiphene citrate (CC) and letrozole on endometrial receptivity for ovulation induction in women with polycystic ovary syndrome (PCOS). A randomized controlled study included 160 patients diagnosed with PCOS, out of which 80 patients received 50 mg of CC and 80 patients received 2.5 mg of letrozole for successful ovulation induction. Endometrial thickness and pattern, the blood flow of uterine artery and subendometrial region, endometrial volume and vascularization index were measured. The ratio of multilayered endometrial pattern in letrozole group was significantly increased on the day of human chorionic gonadotropin (hCG) administration compared with CC group (77.5% vs. 55.0%). The volume, vascularization index (VI), flow index (FI), and vascularization flow index (VFI) of endometrium on the day of hCG administration and 7-9 days after ovulation in letrozole group were significantly increased. The biochemical pregnancy rate, clinical pregnancy rate, and ongoing pregnancy rate in letrozole group were significantly increased compared with CC group (36.3%, 30.0%, 22.5% vs. 21.3%, 13.8%, 10.0%, respectively). Letrozole increased pregnancy rates by improving endometrial receptivity compared with CC in patients with PCOS.

Innovations in assisted reproductive technologies: impact on contemporary donor egg practice and future advances

Innovations in assisted reproductive technologies (ART) have driven progress in the donor egg field since the birth of the first baby derived from a donor egg in 1983. Over time, donor oocytes have become an increasingly used option for patients unable to conceive with autologous oocytes. In donor egg, the unique separation of the oocyte source and recipient uterus has created a model that has propelled advances in ART. Progressive ART innovations that have optimized the oocyte donor and resulting embryo include the following: evaluation of ovarian reserve, controlled ovarian hyperstimulation regimens that reduce the risk of ovarian hyperstimulation syndrome, blastocyst culture, oocyte cryopreservation, and preimplantation genetic testing. For donor egg recipients, methods to optimize the endometrium to maximize implantation include endometrial receptivity testing, immunologic donor-recipient matching, and increased understanding of the uterine microbiome.