Lack of correlation between ultrasonography and histologic staging of the endometrium in in vitro fertilization (IVF) patients

Radiomics optimizing the evaluation of endometrial receptivity for women with unexplained recurrent pregnancy loss

Background

The optimization of endometrial receptivity (ER) through individualized therapies has been shown to enhance the likelihood of successful gestation. However, current practice lacks comprehensive methods for evaluating the ER of patients with recurrent pregnancy loss (RPL). Radiomics, an emerging AI-based technique that enables the extraction of mineable information from medical images, holds potential to offer a more objective and quantitative approach to ER assessment. This innovative tool may facilitate a deeper understanding of the endometrial environment and enable clinicians to optimize ER evaluation in RPL patients.

Objective

This study aimed to identify ultrasound radiomics features associated with ER, with the purpose of predicting successful ongoing pregnancies in RPL patients, and to assess the predictive accuracy of these features against regular ER parameters.

Methods

This retrospective, controlled study involved 262 patients with unexplained RPL and 273 controls with a history of uncomplicated full-term pregnancies. Radiomics features were extracted from ultrasound endometrial segmentation images to derive a radiomics score (rad-score) for each participant. Associations between rad-scores, baseline clinical variables, and sonographic data were evaluated using univariate and multivariate logistic regression analyses to identify potential indicators of RPL. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive accuracy of the rad-score and other identified indicators in discriminating RPL cases. Furthermore, the relationships between age and these identified indicators were assessed via Pearson correlation analysis.

Results

From the 1312 extracted radiomics features, five non-zero coefficient radiomics signatures were identified as significantly associated with RPL, forming the basis of the rad-score. Following multivariate logistic regression analysis, age, spiral artery pulsatility index (SA-PI), vascularisation index (VI), and rad-score emerged as independent correlates of RPL (all P<0.05). ROC curve analyses revealed the superior discriminative capability of the rad-score (AUC=0.882) over age (AUC=0.778), SA-PI (AUC=0.771), and VI (AUC=0.595). There were notable correlations between age and rad-score (r=0.275), VI (r=-0.224), and SA-PI (r=0.211), indicating age-related variations in RPL predictors.

Conclusion

This study revealed a significant association between unexplained RPL and elevated endometrial rad-scores during the WOI. Furthermore, it demonstrated the potential of rad-scores as a promising predictive tool for successful ongoing pregnancies in RPL patients.

Does the ultrasound appearance of the endometrium during treatment with assisted reproductive technologies influence pregnancy outcomes?

We evaluated endometrial pattern, defined as the relative echogenicity of the endometrium on a longitudinal uterine ultrasonic section, as a surrogate for endometrial receptivity in an attempt to evaluate the association between endometrial pattern and pregnancy outcome in women who underwent ART treatment. The primary outcome was live birth and secondary outcomes were clinical intrauterine pregnancy and miscarriage. Potential associations were evaluated using cluster-weighted generalized estimating equations to account for within-couple correlation among repeated ART cycles while adjusting for potentially confounding variables. There were 1034 ART cycles with embryo transfer (778 fresh, 256 frozen) among 695 women (median age: 31.0 (6.0) years). The average number of embryos transferred per cycle was 2.1. The clinical intrauterine pregnancy rate per transfer was 56.0% for fresh and 54.3% for frozen cycles. The overall live birth rate per embryo transfer was 48.4%. Live birth rates were unchanged when the endometrium was semi-trilinear (RR:0.91 CI:0.74,1.12) or unilinear (RR:1.15 CI:0.89,1.49) in comparison to trilinear endometrium after controlling for potentially confounding variables. Results were similar when analysed separately for fresh and frozen cycles and when evaluating associations with clinical intrauterine pregnancy and miscarriage rates. It appears that endometrial pattern does not significantly affect live birth in ART and our data do not support cancelling an ART cycle if the endometrium is less than trilinear.

Ultrasound molecular imaging of vascular endothelial growth factor receptor 2 expression for endometrial receptivity evaluation

Purpose: Ultrasound (US) molecular imaging by examining the expression of vascular endothelial growth factor receptor 2 (VEGFR2) on uterus vascular endothelium was applied to evaluate the endometrial receptivity.

Methods: VEGFR2-targeted ultrasound contrast agents (UCA) and the control UCA (without VEGFR2) were prepared and characterized. Adhesion experiment in vitro was performed with mouse microvascular endothelial cells (bEnd.3) and the ratio of the number of UCA to that of cells at the same field was compared. In vivo study, randomized boluses of targeted or control UCA were injected into the animals of non-pregnancy (D0), pregnancy on day 2 (D2) and day 4 (D4), respectively. Sonograms were acquired by an ultrasound equipment with a 40-MHz high-frequency transducer (Vevo 2100; VisualSonics, Toronto, Canada). The ultrasonic imaging signals were quantified as the video intensity amplitudes generated by the attachment of VEGFR2-targeted UCA. Immunoblotting and immunofluorescence assays were used for confirmation of VEGFR2 expression.

Results: Our results showed that VEGFR2-targeted UCA could bind to bEnd.3 cells with significantly higher affinity than the control UCA (9.8 ± 1.0 bubbles/cell versus 0.7 ± 0.3 bubbles/cell, P < 0.01) in vitro. The mean video intensity from the US backscattering of the retained VEGFR2-targeted UCA was significantly higher than that of the control UCA in D2 and D4 mice (D2, 10.5 ± 2.5 dB versus 1.5 ± 1.1 dB, P < 0.01; D4, 15.7 ± 4.0 dB versus 1.5 ± 1.2 dB, P < 0.01), but not significantly different in D0 mice (1.0 ± 0.8 dB versus 0.9 ± 0.6 dB, P > 0.05). Moreover, D4 mice showed the highest video intensity amplitude, indicating the highest VEGFR2 expression when compared with D2 and D0 mice (P < 0.01). This was further confirmed by our immunoblotting and immunofluorescence experiments.

Conclusion: Ultrasound molecular imaging with VEGFR2-targeted UCA may be used for noninvasive evaluation of endometrial receptivity in murine models.

Use of the natural cycle and vitrification thawed blastocyst transfer results in better in-vitro fertilization outcomes : cycle regimens of vitrification thawed blastocyst transfer

PURPOSE

To compare the IVF outcomes of vitrification-thawed blastocyst transfer cycles utilizing different endometrial preparation methods.

METHODS

We retrospectively assessed IVF outcomes in 611 patients (648 cycles) who underwent blastocyst frozen embryo transfer (FET) between January 2007 and December 2009. All embryos had been cryopreserved by a vitrification method following a previous IVF cycle. Patients were prepared for transfer by using either the natural cycle (n = 310/Group 1), the natural cycle with ovulation induction employing human chorionic gonadotropin (n = 134/Group 2), or a hormonally manipulated artificial cycle with estrogen and progesterone supplementation (n = 204/Group 3).

RESULTS

Multivariate logistic regression analysis showed a significant difference in clinical pregnancy rate between Groups 3 (30.4%) and 1 (41.9%) (odds ratio [OR], 0.567; 95% confidence interval [CI], 0.379-0.847, P = 0.006) whereas the difference between Groups 2 and 1 was not significant (41.8% vs. 41.9%; OR, 0.683; 95% CI, 0.435-1.073; P = 0.098). Other significant variables affecting clinical pregnancy rate were the number of embryos transferred, the grade of transferred embryos, and maximal endometrial thickness.

CONCLUSION

The results showed that, using vitrification-thawed blastocyst transfer, employment of natural cycles with or without hCG treatment was associated with better outcomes than was the use of hormonally manipulated cycles.

Implantation failure: molecular mechanisms and clinical treatment

BACKGROUND

Implantation is a complex initial step in the establishment of a successful pregnancy. Although embryo quality is an important determinant of implantation, temporally coordinated differentiation of endometrial cells to attain uterine receptivity and a synchronized dialog between maternal and embryonic tissues are crucial. The exact mechanism of implantation failure is still poorly understood.

METHODS

This review summarizes the current knowledge about the proposed mechanisms of implantation failure in gynecological diseases, the evaluation of endometrial receptivity and the treatment methods to improve implantation.

RESULTS

The absence or suppression of molecules essential for endometrial receptivity results in decreased implantation rates in animal models and gynecological diseases, including endometriosis, hydrosalpinx, leiomyoma and polycystic ovarian syndrome. The mechanisms are diverse and include abnormal cytokine and hormonal signaling as well as epigenetic alterations.

CONCLUSIONS

Optimizing endometrial receptivity in fertility treatment will improve success rates. Evaluation of implantation markers may help to predict pregnancy outcome and detect occult implantation deficiency. Treating the underlying gynecological disease with medical or surgical interventions is the optimal current therapy. Manipulating the expression of key endometrial genes with gene or stem cell-based therapies may some day be used to further improve implantation rates.

[Views of each member of an Assisted Reproductive Technologies centre on the embryo transfer procedure]

The embryo transfer (ET) is probably the key step of Assisted Reproductive Technologies (ART), end point of the collaboration of a multidisciplinary clinical team and an infertile couple. Thus, a perfect knowledge of available data regarding ET is required to optimize the results of ART. Indeed, numerous published studies demonstrate the impact of defined parameters onto the effectiveness of ET procedure. The aim of this study is to provide views of physicians dealing with ART, i.e. endocrinologist, ultrasound scan specialist, surgeon and biologist to put in perspective questions and answers about ET.

HB-EGF but not amphiregulin or their receptors HER1 and HER4 is altered in endometrium of women with unexplained infertility

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) and its receptors (HER1 and HER4) play a role in the human implantation process. Amphiregulin is a member of the EGF family but with unknown function in human fertility. It has been suggested that some women with unexplained infertility have defective endometrial development. The aim of this study is to determine the presence of amphiregulin and the receptors HER1 and HER4 in normal human endometrium throughout the menstrual cycle. In addition, the present study aims to compare endometrium from women with unexplained infertility with endometrium from women with male factor infertility and healthy fertile controls. Immunohistochemistry and real-time polymerase chain reaction were used to determine the expression of HB-EGF, HER1, HER4, and amphiregulin. The stromal staining of HER1 and the epithelial staining of HER4 were most intense in the mid- and late-secretory-phase endometrium. Amphiregulin did not vary during the menstrual cycle. In the mid-secretory phase, the protein expression of HB-EGF was lower in endometrium from women with unexplained infertility versus normal endometrium and endometrium from women with male factor infertility. HB-EGF and HER4 mRNA expression in mid-secretory endometrium of women with unexplained and male factor infertility were increased compared with normal controls. Impaired endometrial expression of certain members of the EGF family may contribute to infertility in some women with unexplained infertility.

Uterine receptivity to human embryonic implantation: histology, biomarkers, and transcriptomics

Embryonic implantation is a dynamic process of paracrine interactions between the maternal compartment and the conceptus and involves a receptive endometrium and a developmentally competent blastocyst. Herein, we review histology, clinical approaches, and the promise of transcriptomics in elucidating mechanisms underlying implantation and development of biomarkers of uterine receptivity-with an eye to diagnose and treat implantation-based disorders of miscarriage, fetal growth restriction, pre-eclampsia, and infertility.

Three-dimensional ultrasound assessment of endometrial receptivity: a review

Three-dimensional ultrasound (3D US) is a new imaging modality, which is being introduced into clinical practice. Although this technique will not probably replace two-dimensional ultrasound, it is being increasingly used. It has been reported that 3D US is a very high reproducible technique. The endometrium has been paid special attention when using this technique. The aim of this paper is to address some technical aspects of 3D US and to review critically its current status in evaluating endometrial function with special focus in its role in predicting pregnancy in assisted reproductive techniques. In spontaneous cycles endometrial volume grows during follicular phase remaining constant through the luteal phase. Endometrial vascularization increases during follicular phase peaking 2-3 days before ovulation, decreasing thereafter and increasing again during mid and late luteal phase. Data from studies analysing the role of 3D US for predicting IVF outcome are controversial. An explanation for these controversial findings might be different design of reported studies, specially the timing of ultrasound evaluation.

The human endometrium as a fertility-determining factor

Intensive research work has been performed to better understand the regulation of the endometrium and its clinical implications to improve implantation. Although many proteins and molecules may influence endometrial development, their co-ordinated contribution to the implantation process is still poorly understood and a translation into clinical use has not sufficiently been performed. Clinical evaluation of the endometrium by ultrasound and other techniques, like endometrial biopsy and analysis of uterine secretions, has been intensively studied and therapeutic options to improve endometrial function have been suggested and tested. Systemic treatment with heparin, aspirin or corticosteroids did not result in improved implantation rates. Gene therapy and cervical treatment, e.g. with seminal plasma, are still in the phase of clinical research. Therefore, this review focuses on different aspects of endometrial research, which all contribute to the diagnosis, evaluation and therapy of endometrial function and dysfunction. First, the endometrial development towards a receptive milieu is described. Second, the actual clinical evaluation of endometrial receptivity, possible therapeutic strategies and in particular, the evaluation of endometrial function in the non-natural situation of hormonal stimulation is critically evaluated. In conclusion, the endometrium shall be considered as an important fertility-determining factor and therapeutic options should be developed in near future.

Endometrial receptivity: Clinical assessment in relation to fertility, infertility, and antifertility

Fertility in humans and other mammalian species depends absolutely on synchronous events that render the developing blastocyst and the receiving uterus competent for implantation. Endometrial receptivity is defined as the period during which the endometrial epithelium acquires functional, but transient, ovarian steroid-dependent status supportive to blastocyst acceptance and implantation. Once inside the uterus, the blastocyst is surrounded by an intact luminal epithelium, which is considered to act as barrier to its attachment, except for this short period of high endometrial receptivity to blastocyst signal(s). Its transport and permeability properties, in conjunction with cellular action of the endometrium and the embryo, have been suggested to influence creation and maintenance of informational and nutritional status of uterine luminal milieu. This period, also termed as the 'window of implantation,' is limited to days 20-24 of menstrual cycle in humans. However, establishment of endometrial receptivity is still a biological mystery that remains unsolved despite marked advances in our understanding of endometrial physiology following extensive research associated with its development and function. This review deals with various structural, biochemical, and molecular events in the endometrium coordinated within the implantation window that constitute essential elements in the repertoire that signifies endometrial receptivity and is aimed to achieve a better understanding of its relationship to fertility, infertility, and for the development of targeted antifertility agents for human use and welfare.

Endometrial development in association with ovarian follicular waves during the menstrual cycle

OBJECTIVES

Waves of ovarian follicular development during the menstrual cycle have recently been documented in our laboratory. The objective of this study was to test the hypothesis that ultrasonographically detectable changes in the endometrium during the menstrual cycle would differ between women with two vs. three waves of ovarian follicular development and among women with different major and minor wave patterns of follicle growth.

METHODS

Fifty women of reproductive age (mean age +/- SD, 28.0 +/- 6.9 years) underwent daily transvaginal ultrasonography for one interovulatory interval (IOI). Ultrasonographic images of the endometrium were obtained each day, and measurements of endometrial area and perimeter (based on the shape of an ellipse, in the transverse plane) and thickness and pattern (in the sagittal plane) were recorded. Endometrial area, perimeter, thickness and pattern were compared between women with two and three waves of follicle development and among women with different minor and major wave patterns of follicular growth during the IOI.

RESULTS

Endometrial area, perimeter, thickness and pattern increased earlier during the follicular phase in women with two vs. three waves of follicular development. In women with two follicle waves, endometrial area and perimeter increased earlier in those with major major vs. minor major follicle wave patterns.

CONCLUSIONS

Ultrasonographically detectable changes in the endometrium occurred in association with follicle wave dynamics in women. Earlier development of the endometrium during the follicular phase in women with two vs. three follicle waves was attributed to an earlier increase in dominant follicle estradiol production.

Imaging the endometrium: are there predictors of uterine receptivity?

Ultrasound imaging technology brings new insight to cyclic changes in the endometrium and offers the potential to assess the probability of embryo implantation in natural and assisted reproduction cycles. However, the data reported are diverse and frequently conflict in their analysis and conclusions. This review examines imaging techniques used for endometrial evaluation, including grey-scale ultrasonography and colour-flow, power-flow, and spectral Doppler interrogation of the uterine vasculature. New techniques being used for uterine assessment, such as computer-assisted image analysis, three-dimensional ultrasonography, and magnetic resonance imaging, are also discussed. Each of these techniques is under active investigation and has the potential to provide rapid, noninvasive endometrial evaluation. Currently, there is reasonable certainty that women with heterogeneous endometrial linings of less than 6 mm will rarely conceive, and that endometrial contractions, or lack thereof, play some role in the successful establishment of pregnancy, even though this role has not yet been identified. Given the set of new imaging technologies available, it is feasible to expect that visual assessments will someday be used as predictors of uterine receptivity.

Predicting the histologic dating of an endometrial biopsy specimen with the use of Doppler ultrasonography and hormone measurements in patients undergoing spontaneous ovulatory cycles

OBJECTIVE

To examine the relation between uterine blood flow and endometrial thickness on transvaginal Doppler ultrasonography, serum E2 and progesterone levels, and the histologic dating of an endometrial biopsy specimen obtained in the midluteal phase of a spontaneous cycle.

DESIGN

Prospective clinical study.

SETTING

A tertiary care infertility center.

PATIENT(S)

One hundred fifty-nine patients with normal menstrual cycles.

INTERVENTION(S)

Transvaginal Doppler ultrasonographic evaluation of uterine blood flow and endometrial thickness, determination of serum concentrations of E2 and progesterone, and endometrial biopsy.

MAIN OUTCOME MEASURE(S)

Resistance index, pulsatility index, serum E2 and progesterone levels, endometrial thickness, and histologic dating of the endometrium.

RESULT(S)

One hundred thirteen (71%) of the endometrial biopsy specimens showed complete secretory transformation and thus were classified as "in phase," and 46 (29%) of the specimens lacked some or all of the criteria for secretory transformation and thus were classified as "out of phase." There was no statistically significant difference between the in phase and out of phase groups with regard to patient age, endometrial thickness, serum hormone levels, or resistance index. The pulsatility index was significantly higher in the in phase group. The overall predictive value of the studied parameters was only 64% (sensitivity, 57%; specificity, 66%).

CONCLUSION(S)

Doppler ultrasonographic evaluation of uterine blood flow and measurement of hormone concentrations cannot be used to predict the histologic dating of an endometrial biopsy specimen obtained in the midluteal phase of a spontaneous cycle.

Assessment of endometrial volume by three-dimensional ultrasound prior to embryo transfer: clues to endometrial receptivity

The aim of the present prospective study was to obtain quantitative data on endometrial volume by three-dimensional (3D) ultrasound at the time of embryo transfer in an in-vitro fertilization programme and to assess its value in predicting endometrial receptivity. The cycles (n = 72) were classified according to endometrial volume: group A <2 ml, group B 2-4 ml, and group C >4 ml. Comparisons of the groups showed that pregnancy and implantation rates were significantly lower (P < 0.05) in the group of patients with an endometrial volume <2 ml. Furthermore, no pregnancy was achieved with an endometrial volume <1 ml. It is concluded that endometrial volume by 3D transvaginal ultrasound may become a new objective parameter by which to predict endometrial receptivity.