A prospective study of echographic endometrial characteristics and pregnancy rates during hormonal replacement cycles

Effect of collagen endometrial patch loaded with adipose-derived mesenchymal stem cells on endometrial regeneration in rats with a thin endometrium

Background

This study aimed to investigate the effects of a collagen endometrial patch (EM patch) loaded with adipose-derived mesenchymal stem cells (ADSCs) on endometrial regeneration in a rat model with thin endometrium.

Materials and methods

Thin endometrium was induced in female rats and divided into treatment groups as outlined: control, group 1(G1), local injection of ADSCs into the uterus, group 2 (G2), an EM patch without ADSCs, group 3 (G3), and an EM patch loaded with ADSCs, group 4 (G4). The rats were euthanized at either two weeks or four weeks after modeling and treatment followed by histological and biochemical analyses to examine the regenerative effects on the injured endometrium.

Results

Transplantation of the ADSC-loaded EM patch significantly promoted endometrial proliferation and increased the luminal epithelial area. Two weeks after treatment, the mean number of von Villebrand factor (vWF)+ or cluster of differentiation (CD) 31+-stained blood vessels was significantly higher in G4 than in G1 and G2. The mRNA and protein expression levels of TGF-β and FGF2 were significantly upregulated in G4 compared to those in the control. G4 exhibited significantly increased LIF mRNA levels and immunoreactivity compared with the other groups at both two weeks and four weeks after treatment. Cell tracking after ADSCs treatment revealed the presence of a substantial number of ADSCs grafted in the uterine tissues of G4, whereas a low number of ADSCs that were focally clustered were present in G2.

Conclusion

Transplantation of EM patches loaded with ADSCs resulted in the histological and biochemical restoration of an injured endometrium. The strategic integration of EM patches and ADSCs holds significant promise as an innovative therapeutic approach for effectively treating impaired endometrial conditions.

Management of a Thin Endometrium by Hysteroscopic Instillation of Platelet-Rich Plasma Into The Endomyometrial Junction: A Pilot Study

In patients whose embryo transfer has been previously canceled due to a thin endometrium, the injection of platelet-rich plasma (PRP) guided by hysteroscopy into the endomyometrial junction improves endometrial thickness and vascularity. This may well serve as a novel approach for the management of these patients. In this study, 32 patients aged between 27 and 39 years, suffering from primary or secondary infertility, were selected for hysteroscopic instillation of PRP. This cross-sectional study included a retrospective assessment of the improvement of endometrial thickness (>7 mm) on the commencement of progesterone treatment in 24 of 32 patients (75%) after hysteroscopy-guided injections of PRP into the subendometrial zone. After PRP instillation, the endometrium was 7 mm or thicker in 24 of 32 patients, and all 24 patients underwent frozen embryo transfer. Moreover, 12 of 24 patients who underwent embryo transfer conceived, whereas 10 had a clinical pregnancy with visualization of cardiac activity at 6 weeks and two had a biochemical pregnancy. Our approach of PRP injection into the subendometrial region is consistent with the histologically proven regeneration of the endometrium from the endomyometrial junction. We observed an improvement of endometrial thickness and higher pregnancy rates in cases of previously canceled embryo transfer due to a thin endometrium.

Endometrium segmentation on transvaginal ultrasound image using key-point discriminator

PURPOSE

Transvaginal ultrasound imaging provides useful information for diagnosing endometrial pathologies and reproductive health. Endometrium segmentation in transvaginal ultrasound (TVUS) images is very challenging due to ambiguous boundaries and heterogeneous textures. In this study, we developed a new segmentation framework which provides robust segmentation against ambiguous boundaries and heterogeneous textures of TVUS images.

METHODS

To achieve endometrium segmentation from TVUS images, we propose a new segmentation framework with a discriminator guided by four key points of the endometrium (namely, the endometrium cavity tip, the internal os of the cervix, and the two thickest points between the two basal layers on the anterior and posterior uterine walls). The key points of the endometrium are defined as meaningful points that are related to the characteristics of the endometrial morphology, namely the length and thickness of the endometrium. In the proposed segmentation framework, the key-point discriminator distinguishes a predicted segmentation map from a ground-truth segmentation map according to the key-point maps. Meanwhile, the endometrium segmentation network predicts accurate segmentation results that the key-point discriminator cannot discriminate. In this adversarial way, the key-point information containing endometrial morphology characteristics is effectively incorporated in the segmentation network. The segmentation network can accurately find the segmentation boundary while the key-point discriminator learns the shape distribution of the endometrium. Moreover, the endometrium segmentation can be robust to the heterogeneous texture of the endometrium. We conducted an experiment on a TVUS dataset that contained 3,372 sagittal TVUS images and the corresponding key points. The dataset was collected by three hospitals (Ewha Woman's University School of Medicine, Asan Medical Center, and Yonsei University College of Medicine) with the approval of the three hospitals' Institutional Review Board. For verification, fivefold cross-validation was performed.

RESULT

The proposed key-point discriminator improved the performance of the endometrium segmentation, achieving 82.67 % for the Dice coefficient and 70.46% for the Jaccard coefficient. In comparison, on the TVUS images UNet, showed 58.69 % for the Dice coefficient and 41.59 % for the Jaccard coefficient. The qualitative performance of the endometrium segmentation was also improved over the conventional deep learning segmentation networks. Our experimental results indicated robust segmentation by the proposed method on TVUS images with heterogeneous texture and unclear boundary. In addition, the effect of the key-point discriminator was verified by an ablation study.

CONCLUSION

We proposed a key-point discriminator to train a segmentation network for robust segmentation of the endometrium with TVUS images. By utilizing the key-point information, the proposed method showed more reliable and accurate segmentation performance and outperformed the conventional segmentation networks both in qualitative and quantitative comparisons.

Therapeutic Effects of VEGF Gene-Transfected BMSCs Transplantation on Thin Endometrium in the Rat Model

Objective

Bone mesenchymal stem cells (BMSCs) transplantation has a therapeutic effect on the thin endometrium in animal researches and clinical trials. The present study aims at assessing whether transplantation of VEGF-transfected BMSCs (VEGF-BMSCs) have a better therapeutic effect on endometrial regeneration and endometrial receptivity compared with BMSCs therapy alone.

Methods

Sprague-Dawley (SD) rats were used in the study. Thin endometrium model was established with 95% ethanol injection into uterine. VEGF-BMSCs or BMSCs was transplanted via tail vein IV injection. Endometrial thickness, morphology, and pinopodes were assessed by hematoxylin and eosin (HE) staining and scanning electron microscope (SEM). The proteins and mRNAs expressions of markers for endometrial cells and endometrial receptivity were measured after treatment. The fertility testing was done to assess the embryo implantation efficiency.

Results

VEGF-BMSCs transplantation significantly increased endometrial thickness compared with the BMSCs group and the control group. There was no significant difference in endometrial thickness between VEGF-BMSCs group and sham operation group. Importantly, in protein level, expressions of cytokeratin, vitamin, VEGF, LIF, and integrin α_νβ ₃ in VEGF-BMSC group were increased dramatically compared with those of the control group and BMSC group both 4 days and 8 days after stem cells transplantation. Accordingly, mRNA expression of LIF and integrin α _ν β ₃ was significantly upregulated compared with those of the control group and BMSC group both 4 and 8 days after treatment. The pinopodes were developed better in the VEGF-BMSCs group and the sham operation group compared with BMSCs group and the control group. The number of embryo implantation is largest in the sham operation group, followed by VEGF-BMSCs group, BMSCs group, and the control group.

Conclusions

Transplantation of VEGF gene-transfected BMSCs may be a better therapeutic treatment for thin endometrium than stem cell therapy alone.

Insufficient Angiogenesis: Cause of Abnormally Thin Endometrium in Subfertile Patients?

INTRODUCTION

This study investigated subfertile patients with abnormally thin endometrium after infertility treatment. As they had adequate serum concentrations of hormones, an endometrial factor for subfertility was suspected.

METHODS

To elucidate the cause of subfertility, endometrial biopsies were taken in each patient in the late proliferative and mid-secretory phases of one menstrual cycle. Endometrial biopsies from women with normal menstrual cycles and confirmed fertility who were undergoing hysterectomy for benign uterine disease were used as positive controls. The tissue samples were investigated for steroid hormone receptor expression and for the proliferation marker Ki-67. Immunohistochemistry was performed with antibodies against the marker molecules for endometrial receptivity - β ₃ integrin, VEGF, LIF, and CD56 (large granular lymphocytes, LGLs).

RESULTS

The steroid hormone receptors for estrogen (E2) and progesterone (P) were expressed normally (at the first biopsy) and were down-regulated (at the second biopsy) within the cycle. Strikingly, all of the marker molecules investigated showed negative or weak and inadequate expression in the mid-secretory phase. Numbers of LGLs remained as low as in the proliferative phase. In contrast, fertile patients were found to express these marker molecules distinctly in the mid-secretory phase.

CONCLUSIONS

It may be hypothesized that a severe deficiency of these angiogenesis-related marker molecules leads to defective development of the endometrium, which remains thin. Deficient angiogenetic development may thus provide an explanation for the endometrial factor that causes infertility. Further investigations will need to focus on identifying the regulating factors that act between steroid receptor activation and the expression of these marker molecules.

Thin endometrium transcriptome analysis reveals a potential mechanism of implantation failure

Aim

Although a thin endometrium has been well recognized as a critical factor in implantation failure, little information is available regarding the molecular mechanisms. The present study investigated these mechanisms by using genome‐wide mRNA expression analysis.

Methods

Thin and normal endometrial tissue was obtained from a total of six women during the mid‐luteal phase of the menstrual cycle. The transcriptomes were analyzed with a microarray. Differentially expressed genes were classified according to Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways.

Results

The study identified 318 up‐regulated genes and 322 down‐regulated genes in the thin endometrium, compared to the control endometrium. The GO and KEGG pathway analyses indicated that the thin endometrium possessed aberrantly activated immunity and natural killer cell cytotoxicity that was accompanied by an increased number of inflammatory cytokines, such as IFN‐γ. Various genes that were related to metabolism and anti‐oxidative stress were down‐regulated in the thin endometrium.

Conclusion

Implantation failure in the thin endometrium appears to be associated with an aberrantly activated inflammatory environment and aberrantly decreased response to oxidative stress.

ART and uterine pathology: how relevant is the maternal side for implantation?

BACKGROUND

Assisted reproduction technology (ART) has become a standard treatment for infertile couples. Increased success rates obtained over the years have resulted primarily from improved embryo quality, but implantation rates still remain lower than expected. The uterus, an important player in implantation, has been frequently neglected. While a number of uterine pathologies have been associated with decreased natural fertility, less information exists regarding the impact of these pathologies in ART. This report reviews the evidence to help clinicians advise ART patients.

METHODS

An electronic search of PubMed and EMBASE was performed to identify articles in the English, French or Spanish language published until May 2014 which addressed uterine pathology and ART. Data from natural conception were used only in the absence of data from ART. Studies were classified in decreasing categories: RCTs, prospective controlled trials, prospective non-controlled trials, retrospective studies and experimental studies. Studies included in lower categories were only used if insufficient evidence was available. Pooled data were obtained from systematic reviews with meta-analyses when available. The summary of the evidence for the different outcomes and the degree of the recommendation for interventions were based on the GRADE (Grading of Recommendations Assessment, Development and Evaluation) statement recommendations.

RESULTS

There is strong evidence that surrogacy is effective for uterine agenesia. For the remaining pathologies, however, there is very little evidence that the established treatments improve outcomes, or that these pathologies have a negative effect on ART. In the presence of an apparently normal uterus, assessing endometrial receptivity (ER) is the goal; however diagnostic tests are still under development.

CONCLUSIONS

The real effect of different uterine/endometrial integrity pathologies on ART is not known. Moreover, currently proposed treatments are not based on solid evidence, and little can be done to assess ER in normal or abnormal conditions. No strong recommendations can be given based on the published experience, bringing an urgent need for well-designed studies. In this context, we propose algorithms to study the uterus in ART.

Treating patients with "thin" endometrium - an ongoing challenge

OBJECTIVE

To review the literature regarding inadequate growth ("thin") of the endometrium and to present the hitherto published methods aimed to improve endometrial thickness and the consequent endometrial receptivity.

MATERIALS AND METHODS

A literature review was conducted for all relevant articles assessing the effect of various treatment modalities on "thin" endometrium and the consequent reproductive outcome.

RESULTS

Several treatment modalities have been offered to patients with "thin" endometrium, including hysteroscopic adhesiolysis, hormonal manipulation by estrogen and GnRH-agonist, vasoactive measures such as aspirin, vitamin E, pentoxifylline, l-arginine or sildenafil, intra-uterine infusion of growth factor such as G-CSF and the recent application of regenerative medicine. In spite of the vast diversity of treatment, most of the options accomplish only minor change in the endometrium thickness and subsequent pregnancy rate, and when they fail, patients are usually referred to surrogacy.

CONCLUSIONS

"Thin" endometrium is known to adversely affect reproductive performance. Treatment of "thin endometrium" remains a challenge and future large researches are required to further elucidate and optimal management of patients with "thin" endometrium.

A pilot study to prevent a thin endometrium in patients undergoing clomiphene citrate treatment

BACKGROUND

Clomiphene citrate (CC) is most commonly used as a first-line treatment of infertility. However, a disturbance of endometrial growth by the adverse effects of the CC has been recognized. Since a thin endometrium is recognized as a critical factor of implantation failure, preventing CC-induced thinning of the endometrium is important. This study was undertaken to investigate whether the modified CC treatments are useful to prevent a thin endometrium in patients undergoing CC treatments.

METHODS

This study is a prospective, randomized controlled study. The study was performed at the Saiseikai Shimonoseki General Hospital during a 4-month period (May 2012 to September 2012). Sixty-six infertile women who had a thin endometrium (< 8 mm) during the standard CC treatment (50 mg/day on days 5-9 of the menstrual cycle) were enrolled. The patients were randomly divided into three groups: 22 patients were given 25 mg/day CC on days 5-9 (half-dose group), 22 patients were given 50 mg/day CC on days 1-5 (early administration group) and 22 patients received a standard CC treatment again (control group). Endometrial thickness at the induction of ovulation was assessed by ultrasonography. The primary endpoint of this study was an endometrial thickness.

RESULTS

Half dose administration and early administration improved the endometrial thickness (≥ 8 mm) in 14 patients (70%) and in 19 patients (90%) respectively, while only 3 patients (15%) improved in endometrial thickness in the control group. The mean endometrial thickness was also significantly higher in the half dose group (8.6 ± 1.5 mm) and early administration group (9.4 ± 1.5 mm) compared to the control group (6.7 ± 1.8 mm). No side effect was observed in this study.

CONCLUSIONS

The modified treatment with a half-dose or early administration of CC significantly increased endometrial thickness in patients with a history of thin endometrium caused by the standard CC regimen. The modified CC treatments in this study can be beneficial for patients with a thin endometrium as a result of standard CC treatment.

TRIAL REGISTRATION

CLINICAL TRIAL REGISTRATION NUMBER

UMIN000007959.

A meta-analysis of the relationship between endometrial thickness and outcome of in vitro fertilization cycles

OBJECTIVE:

The objective was to evaluate the relationship between endometrial thickness on the day of human chorionic gonadotropin administration and pregnancy outcome in in vitro fertilization cycles.

DESIGN:

This was a systematic review and meta-analysis.

MATERIALS AND METHODS:

We identified 484 articles using Cochrane library, PubMed, Web of Science, and Embase searches with various key words including endometrial thickness, pregnancy, assisted reproductive technology, endometrial pattern, and in vitro fertilization. A total of 14 studies with data on endometrial thickness and outcome were selected, representing 4922 cycles (2204 pregnant and 2718 nonpregnant). The meta-analysis with a random effects model was performed using comprehensive meta-analysis software. We calculated the standardized mean difference, odds ratio (OR), and 95% confidence intervals (CIs).

RESULTS:

There was a significant difference in the mean endometrial thickness between pregnant and nonpregnant groups (P<0.001), with a standardized mean difference of 0.4 mm (95% CI 0.22–0.58). The OR for pregnancy was 1.40 (95% CI 1.24–1.58).

CONCLUSIONS:

The mean endometrial thickness was significantly higher in pregnant women compared to nonpregnant. The mean difference between two groups was <1 mm which may not be clinically meaningful. Although there may be a relationship between endometrial thickness and pregnancy, implantation potential is probably more complex than a single ultrasound measurement can determine.

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.

Endometrial growth and uterine blood flow: a pilot study for improving endometrial thickness in the patients with a thin endometrium

OBJECTIVE

To examine whether thin endometria can be improved by increasing uterine radial artery (uRA) blood flow.

DESIGN

A prospective observational study.

SETTING

University hospital and city general hospital.

PATIENT(S)

Sixty-one patients with a thin endometrium (endometrial thickness [EM] <8 mm) and high radial artery-resistance index of uRA (RA-RI >or=0.81).

INTERVENTION(S)

Vitamin E (600 mg/day, n = 25), l-arginine (6 g/day, n = 9), or sildenafil citrate (100 mg/day, intravaginally, n = 12) was given.

MAIN OUTCOME MEASURE(S)

EM and RA-RI were assessed by transvaginal color-pulsed Doppler ultrasound.

RESULT(S)

Vitamin E improved RA-RI in 18 (72%) out of 25 patients and EM in 13 (52%) out of 25 patients. L-arginine improved RA-RI in eight (89%) out of nine patients and EM in six (67%) patients. Sildenafil citrate improved RA-RI and EM in 11 (92%) out of 12 patients. In the control group (n = 10), who received no medication to increase uRA-blood flow, only one (10%) patient improved in RA-RI and EM. The effect of vitamin E was histologically examined in the endometrium (n = 5). Vitamin E improved the glandular epithelial growth, development of blood vessels, and vascular endothelial growth factor protein expression in the endometrium.

CONCLUSION(S)

Vitamin E, l-arginine, or sildenafil citrate treatment improves RA-RI and EM and may be useful for the patients with a thin endometrium.

The role of preparatory cycles in ovum donation recipients: a retrospective study

PURPOSE

To determine whether preparatory cycles affect in vitro fertilization (IVF) outcome in ovum donation.

METHODS

Medical records of 98 ovum donation recipients undergoing their first egg donation cycle were analyzed retrospectively. Preparatory cycles were performed in 50 patients with leuprolide acetate, estrogen, and progesterone. An endometrial biopsy was performed on day 10-12 of progesterone supplementation, to determine adequacy of the preparatory cycle.

RESULTS

Pregnancy rates in women with and without preparatory cycles were 42.0% and 43.8%, respectively. Among ovum donation recipients who underwent preparatory cycles, the percentages of adequate endometrial biopsies in pregnant versus nonpregnant groups were 76.2% and 84.3%, respectively. No results showed statistical significance.

CONCLUSIONS

Preparatory cycles do not increase pregnancy rates in ovum donation recipients. In addition, no correlation was noted between adequate endometrial biopsies and higher pregnancy rates.

Subendometrial contractility is not predictive for in vitro fertilization (IVF) outcome

OBJECTIVES

The aim of the study was to investigate whether endometrial thickness, endometrial pattern, endometrial movement and serum estradiol and progesterone affect the outcome of in vitro fertilization.

METHODS

Prospectively collected data of endometrial thickness, endometrial pattern and subendometrial activity were analyzed in 122 consecutive in vitro fertilization cycles. All measurements were made on the day of hCG administration (day -2), day of embryo transfer (day +2), day +6 and day +12.

RESULTS

It would appear that pregnant women tend to have a thicker endometrium on day +12 than non-pregnant women. There appears to be no appreciable difference between pregnant and non-pregnant women in endometrial movement and thickness, nor in serum estradiol and progesterone on day +2 and day +6. In combining three echographic variables (thickness, pattern and movement) and hormone level (estradiol and progesterone), only progesterone on day +12 could be used to predict the outcome.

CONCLUSIONS

Subendometrial contractility plays no important role in implantation on the day of embryo transfer or 4 days later.

Low-dose aspirin for oocyte donation recipients with a thin endometrium: prospective, randomized study

OBJECTIVE

To evaluate the effect of low-dose aspirin use in oocyte donation recipients with an endometrial thickness of < 8 mm.

DESIGN

A prospective, randomized study.

SETTING

An oocyte donation program in a private infertility practice.

PATIENT(S)

Twenty-eight recipients undergoing oocyte donation who failed to develop an endometrial thickness of at least 8 mm in a previous evaluation cycle.

INTERVENTION(S)

Fifteen recipients received low-dose aspirin (81 mg/d) in addition to standard hormone replacement for an oocyte donation cycle. The remaining 13 recipients did not receive aspirin.

MAIN OUTCOME MEASURE(S)

Clinical pregnancy rates, delivery rates, implantation rates, and change in endometrial thickness were compared in the aspirin and nonaspirin groups.

RESULT(S)

There was no demonstrable increase in endometrial thickness in the aspirin-treated group. However, there was a statistically significant increase in implantation rates in the aspirin-treated group (24% versus 9%) and in implantation rates and clinical pregnancy rates in the aspirin-treated group when the final endometrial thickness was < 8 mm.

CONCLUSION(S)

Low-dose aspirin therapy improves implantation rates in oocyte donation recipients with a thin endometrium.

Pregnancy results after ovum donation following one to seven embryo transfers

OBJECTIVE

To determine whether failure to achieve pregnancy after repeated ET after ovum donation was due to an endometrial defect or to the embryo quality.

DESIGN

Retrospective data analysis.

SETTING

A private infertility center.

PATIENT(S)

Four hundred sixty-seven donors (513 cycles) undergoing IVF donating oocytes to 266 recipients (423 cycles).

INTERVENTION(S)

Hormonal endometrial preparation with increasing dosages of valerate E2 (2,4, and 6 mg) and 100 mg of P.

MAIN OUTCOME MEASURE(S)

Pregnancy rates (PRs) and abortion rates in patients undergoing one to seven ETs after ovum donation.

RESULT(S)

Pregnancy rates in recipients that had one or two ETs were significantly higher (34.8%) compared with those of recipients having three or more ETs (15.1%). Abortion rates were significantly higher (54.5%) in recipients repeating more than three ETs than in the recipients having one or two ETs (29.1%).

CONCLUSION(S)

Recipients that had failed to establish a pregnancy after two ETs had a lower PR in successive attempts, possibly because of a defect of their endometrial lining.

Endometrial thickness is predictive of histologic endometrial maturation in women undergoing hormone replacement for ovum donation

OBJECTIVE

To determine if ultrasonographic endometrial pattern or thickness is predictive of histologic endometrial maturation in women undergoing hormone replacement for ovum donation.

DESIGN

Ultrasonographic endometrial thickness and pattern were determined and compared with histologic assessment of endometrial maturation.

PATIENTS

Forty-six women underwent 52 preparatory cycles for ovum donation. Transvaginal ultrasound (US) was performed after 14 days of E2 replacement and, after 12 days of P, an endometrial biopsy was performed. In 12 cycles, a continuous dose of 2 mg/d E2 was administered. In cycles with out-of-phase biopsies (dated earlier than day 24) and in the last 34 cycles, all women received an escalating dose of E2 before initiation of P. Additionally, the 46 women underwent 55 ETs with USs performed on cycle day 15.

RESULTS

Six women had abnormal biopsies in their first preparatory cycle on the continuous E2 protocol, which normalized with the escalating protocol. All other women had normal biopsies. Women with abnormal biopsies had significantly thinner endometrium (< or = 6 mm) but similar endometrial patterns compared with women with normal biopsies. In women having US in preparatory and transfer cycles, there were no differences in endometrial thickness or pattern between examinations.

CONCLUSIONS

Endometrial thickness > or = 7 mm in hormone replacement cycles predicts in phase endometrial histology and can replace the endometrial biopsy.