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Background: In frozen embryo transfer (FET) cycles, optimal endometrial thickness on ovulation day is typically 7–8 mm before progesterone administration. Recent studies have highlighted the significant inverse correlation between ongoing pregnancy rates and changes in endometrial thickness during the secretory phase after progesterone exposure, particularly by the day of embryo transfer (ET). This study aims to investigate how changes in endometrial thickness from the end of the proliferative phase to ET impact FET outcomes. Methods: We conducted a prospective observational cohort study involving 247 FET cycles, divided into hormonally based (102) and ovulatory-based (145) groups. Patients were monitored through transvaginal ultrasound (TVS) and blood tests. On ET day, we assessed endometrial thickness and changes compared to the last day of the proliferative phase, defining endometrial compaction as a decrease in thickness. We analyzed data to identify factors predicting cycle outcomes. Results: The study reported chemical and clinical pregnancy rates of 47.4% and 38.1%, respectively. Endometrial compaction was observed in 37.2% (92/247) of cycles, with corresponding rates of 48.9%, 32.6%, and 29.5% for chemical, clinical, and ongoing pregnancies, compared to 46.4%, 41.3%, and 28.9% in cycles without compaction. These differences were not statistically significant, and patterns of endometrial thickness change were similar across different FET protocols and progesterone exposure durations. Conclusions: The main factors influencing cycle outcomes were maternal age, embryo transfer protocol, and endometrial thickness on ET day, with endometrial compaction showing no correlation with improved outcomes. [ABSTRACT FROM AUTHOR]

STUDY QUESTION Does endometrial compaction (EC) help predict pregnancy outcomes in those undergoing ART? SUMMARY ANSWER EC is associated with a significantly higher clinical pregnancy rate (CPR) and ongoing pregnancy rate (OPR), but this does not translate to live birth rate (LBR). WHAT IS KNOWN ALREADY EC describes the progesterone-induced decrease in endometrial thickness, which may be observed following the end of the proliferative phase, prior to embryo transfer. EC is proposed as a non-invasive tool to help predict pregnancy outcome in those undergoing ART, however, published data is conflicting. STUDY DESIGN, SIZE, DURATION A literature search was carried out by two independent authors using PubMed, Cochrane Library, MEDLINE, Embase, Science Direct, Scopus, and Web of Science from inception of databases to May 2023. All peer-reviewed studies reporting EC and pregnancy outcomes in patients undergoing IVF/ICSI treatment were included. PARTICIPANTS/MATERIALS, SETTING, METHODS The primary outcome is LBR. Secondary outcomes included other pregnancy metrics (positive pregnancy test (PPT), CPR, OPR, miscarriage rate (MR)) and rate of EC. Comparative meta-analyses comparing EC and no EC were conducted for each outcome using a random-effects model if I 2 > 50%. The Mantel–Haenszel method was applied for pooling dichotomous data. Results are presented as odds ratios (OR) with 95% CI. MAIN RESULTS AND THE ROLE OF CHANCE Out of 4030 screened articles, 21 cohort studies were included in the final analysis (n = 27 857). No significant difference was found between LBR in the EC versus the no EC group (OR 0.95; 95% CI 0.87–1.04). OPR was significantly higher within the EC group (OR 1.61; 95% CI 1.09–2.38), particularly when EC ≥ 15% compared to no EC (OR 3.52; 95% CI 2.36–5.23). CPR was inconsistently defined across the studies, affecting the findings. When defined as a viable intrauterine pregnancy <12 weeks, the EC group had significantly higher CPR than no EC (OR 1.83; 95% CI 1.15–2.92). No significant differences were found between EC and no EC for PPT (OR 1.54; 95% CI 0.97–2.45) or MR (OR 1.06; 95% CI 0.92–1.56). The pooled weighted incidence of EC across all studies was 32% (95% CI 26–38%). LIMITATIONS, REASONS FOR CAUTION Heterogeneity due to differences between reported pregnancy outcomes, definition of EC, method of ultrasound, and cycle protocol may account for the lack of translation between CPR/OPR and LBR findings; thus, all pooled data should be viewed with an element of caution. WIDER IMPLICATIONS OF THE FINDINGS In this dataset, the significantly higher CPR/OPR with EC does not translate to LBR. Although stratification of women according to EC cannot currently be recommended in clinical practice, a large and well-designed clinical trial to rigorously assess EC as a non-invasive predictor of a successful pregnancy is warranted. We urge for consistent outcome reporting to be mandated for ART trials so that data can be pooled, compared, and concluded on. STUDY FUNDING/COMPETING INTEREST(S) H.A. was supported by the Hewitt Fertility Centre. S.G.P. and J.W. were supported by the Liverpool University Hospital NHS Foundation Trust. D.K.H. was supported by a Wellbeing of Women project grant (RG2137) and MRC clinical research training fellowship (MR/V007238/1). N.T. was supported by the National Institute for Health and Care Research. D.K.H. had received honoraria for consultancy for Theramex and has received payment for presentations from Theramex and Gideon Richter. The remaining authors have no conflicts of interest to report. REGISTRATION NUMBER PROSPERO CRD42022378464 [ABSTRACT FROM AUTHOR]

STUDY QUESTION Does the change in endometrial thickness (EMT) from the end of the follicular/estrogen phase to the day of embryo transfer (ET) determine subsequent pregnancy outcomes? SUMMARY ANSWER Endometrial compaction from the late-proliferative to secretory phase is not associated with live birth rate (LBR) and other pregnancy outcomes. WHAT IS KNOWN ALREADY Endometrial compaction has been suggested to be indicative of endometrial responsiveness to progesterone, and its association with ET outcome has been investigated but is controversial. STUDY DESIGN, SIZE, DURATION A systematic review with meta-analysis was carried out. PubMed, EMBASE, and Web of Science were searched to identify relevant studies from inception to 18 November 2022. The reference lists of included studies were also manually screened for any additional publications. PARTICIPANTS/MATERIALS, SETTING, METHODS Cohort studies comparing ET pregnancy outcomes between patients with and without endometrial compaction were included. A review of the studies for inclusion, data extraction, and quality assessment was performed by two independent reviewers. The effect size was synthesized as odds ratio (OR) with 95% CI using a random-effects model. Heterogeneity and publication bias were assessed by the I 2 statistic and Egger's test, respectively. The primary outcome was LBR. Secondary outcomes included biochemical pregnancy rate (BPR), clinical pregnancy rate (CPR), miscarriage rate (MR), ongoing pregnancy rate (OPR), and ectopic pregnancy rate (EPR). MAIN RESULTS AND THE ROLE OF CHANCE Seventeen cohort studies involving 18 973 ET cycles fulfilled the eligibility criteria. The pooled results revealed that there were no significant differences between endometrial compaction and non-compaction groups in LBR (crude OR (cOR) = 0.95, 95% CI 0.87–1.04; I 2 = 0%; adjusted OR (aOR) = 1.02, 95% CI 0.87–1.19, I 2 = 79%), BPR (cOR = 0.93, 95% CI 0.81–1.06; I 2 = 0%; aOR = 0.88, 95% CI 0.75–1.03, I 2 = 0%), CPR (cOR = 0.98, 95% CI 0.81–1.18; I 2 = 70%; aOR = 0.86, 95% CI 0.72–1.02, I 2 = 13%), MR (cOR = 1.09, 95% CI 0.90–1.32; I 2 = 0%; aOR = 0.91, 95% CI 0.64–1.31; I 2 = 0%), and EPR (cOR = 0.70, 95% CI 0.31–1.61; I 2 = 61%). The OPR was marginally higher in crude analysis (cOR = 1.48, 95% CI 1.01–2.16; I 2 = 81%) among women with compacted endometrium, but was not evident in adjusted results (aOR = 1.36, 95% CI 0.86–2.14; I 2 = 84%). Consistently, the pooled estimate of LBR remained comparable in further subgroup and sensitivity analyses according to the degree of compaction (0%, 5%, 10%, 15%, or 20%), type of ET (fresh, frozen, or euploid only), and endometrial preparation protocol (natural or artificial). No publication bias was observed based on Egger's test. LIMITATIONS, REASONS FOR CAUTION Although the number of included studies is sufficient, data on certain measures, such as EPR, are limited. The inherent bias and residual confounding were also inevitable owing to the observational study design. Furthermore, inconsistent definitions of pregnancy outcomes may affect the accuracy of our pooled analysis. WIDER IMPLICATIONS OF THE FINDINGS Given the lack of prognostic value, assessing endometrial compaction or repeated EMT measurement on the day of ET may not be necessary or warranted. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by Natural Science Foundation of Jiangxi Province (20224BAB216025), National Natural Science Foundation of China (82260315), and Central Funds Guiding the Local Science and Technology Development (20221ZDG020071). The authors have no conflicts of interest to declare. REGISTRATION NUMBER CRD42022384539 (PROSPERO). [ABSTRACT FROM AUTHOR]

Objective: There is no clear evidence of clinical significance of endometrial compaction, which can be measured by a reduction in endometrial thickness (EMT) during the follicular-luteal transition before the day of embryo transfer. In this study, we aim to determine whether endometrial compaction has an effect on in vitro fertilization (IVF) success. Method(s): We searched PubMed, Cochrane, Embase, and Web of Science electronic databases for studies published in English up to March 2023. Heterogeneity between studies was assessed using the I² statistic. The random effects model and fixed effects model was used to pool the risk ratio (RR) with a corresponding 95% confidence interval (CI). A subgroup analysis was performed based on different methods of ultrasonic measurement and different endometrial compaction rates (ECR). Stata 17.0 software was used for meta-analysis. Pregnancy outcomes, which included clinical pregnancy rate, ongoing pregnancy rate, live birth rate, and spontaneous abortion rate, were evaluated. Result(s): In this study, 18 cohort studies were included, involving 16,164 embryo transfer cycles. Pooled results indicated that there was no significant difference between the endometrial compaction group and the non-compaction group in terms of clinical pregnancy rate (RR [95% CI]=0.98 [0.90,1.08]; I2 = 69.76%), ongoing pregnancy rate (RR [95% CI]=1.18 [0.95,1.47]; I2 = 78.77%), live birth rate (RR [95% CI]= 0.97 [0.92,1.02]; I2 = 0.00%) or spontaneous abortion rate (RR [95% CI]= 1.07[0.97,1.26]; I2 = 0.00%). According to the subgroup analysis of ultrasonic measurement methods, in the transvaginal ultrasound (TVUS) combined with abdominal ultrasonography (AUS) cycles of the endometrial compaction group, the rate of ongoing pregnancy (RR [95% CI] = 1.69 [1.26, 2.26]; I2 = 29.27%) and live birth (RR [95% CI] = 1.27 [1.00,1.61]; I2 = 62.28%) was significantly higher than that of the non-compaction group. Additionally, subgroup analysis based on ECR revealed a significantly higher rate of ongoing pregnancy when ECR ≥ 15% (RR [95% CI] = 1.99 [1.61, 2.47]; I2 = 0.00%). Conclusion: Endometrial compaction has no adverse effect on clinical pregnancy rate, ongoing pregnancy rate, live birth rate, or spontaneous abortion rate. A possible explanation for the contradictory findings of previous studies lies in the method by which the EMT is measured. [ABSTRACT FROM AUTHOR]

Introduction: Embryo implantation is a complex and poorly understood process. Most studies to date have focused on the analysis of the endometrium at the end of the estrogenic phase, while the available data on its importance after secretory transformation are limited and inconsistent. Current evidence does not allow for a conclusive interpretation of the changes observed in the pre-implantation endometrium, whether in the natural or replacement cycle, and their relevance in the development of a pregnancy or the implications for clinical practice. Methods: Multicenter prospective observational cohort study. Based on our sample size calculation, the study group will consist of 206 women (exposed or “compaction” group: 103 women with a decrease of ≥ 5% in endometrial thickness between the estrogenic phase and the day of embryo transfer; non-exposed “non-compaction” group: 103 women with similar or greater endometrial thickness between these time points). The main objective of this study is to compare the ongoing pregnancy rates in natural cycles for euploid embryo transfer in patients who present endometrial compaction at the time of transfer versus those who with a stable or greater endometrial thickness with respect to the estrogenic phase. The estimated duration of the study is 30 months. Inclusion criteria are: 18 to 50 years of age, with primary or secondary infertility, subjected to endometrial preparation in a modified natural cycle for transfer of a genetically euploid blastocyst, from their own oocyte or oocyte donation, with a normal uterine cavity. Exclusion criteria are: uterine or endometrial disease (e.g., multiple myomatosis, severe adenomyosis, Asherman syndrome, refractory endometrium), conditions that prevent correct ultrasound assessment (tilted uterus), or a history of recurrent implantation failure or repeated miscarriages. [ABSTRACT FROM AUTHOR]

Purpose: Endometrial compaction (EC) is defined as the difference in endometrial thickness from the end of the follicular phase to the day of embryo transfer (ET). We aimed to determine the role of EC in predicting assisted reproductive technology (ART) success by conducting a meta-analysis of studies reporting the association between EC and clinical outcomes of ART. Methods: MEDLINE via PubMed, Web of Science, Scopus, and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched from the date of inception to May 19, 2023. The primary outcome was live birth rate (LBR) per ET. Secondary outcomes were live birth or ongoing pregnancy per ET, ongoing pregnancy per ET, clinical pregnancy per ET, and miscarriage per clinical pregnancy. Results: Fifteen studies were included. When data from all studies reporting live birth were pooled, overall LBR rates were comparable in cycles showing EC or not [RR = 0.97, 95%CI = 0.92 to 1.02; 10 studies, 11,710 transfer cycles]. In a subgroup of studies that included euploid ET cycles, a similar LBR for patients with and without EC was noted [RR = 0.99, 95%CI = 0.86 to 1.13, 4 studies, 1172 cycles]. The miscarriage rate did not seem to be affected by the presence or absence of EC [RR = 1.06, 95%CI = 0.90 to 1.24; 12 studies]. Conclusion: The predictive value of EC in determining LBR is limited, and assessment of EC may no longer be necessary, given these findings. Trial registration: PROSPERO CRD42023410389 [ABSTRACT FROM AUTHOR]

IntroductionEmbryo implantation is a complex and poorly understood process. Most studies to date have focused on the analysis of the endometrium at the end of the estrogenic phase, while the available data on its importance after secretory transformation are limited and inconsistent. Current evidence does not allow for a conclusive interpretation of the changes observed in the pre-implantation endometrium, whether in the natural or replacement cycle, and their relevance in the development of a pregnancy or the implications for clinical practice.MethodsMulticenter prospective observational cohort study. Based on our sample size calculation, the study group will consist of 206 women (exposed or “compaction” group: 103 women with a decrease of ≥ 5% in endometrial thickness between the estrogenic phase and the day of embryo transfer; non-exposed “non-compaction” group: 103 women with similar or greater endometrial thickness between these time points). The main objective of this study is to compare the ongoing pregnancy rates in natural cycles for euploid embryo transfer in patients who present endometrial compaction at the time of transfer versus those who with a stable or greater endometrial thickness with respect to the estrogenic phase. The estimated duration of the study is 30 months. Inclusion criteria are: 18 to 50 years of age, with primary or secondary infertility, subjected to endometrial preparation in a modified natural cycle for transfer of a genetically euploid blastocyst, from their own oocyte or oocyte donation, with a normal uterine cavity. Exclusion criteria are: uterine or endometrial disease (e.g., multiple myomatosis, severe adenomyosis, Asherman syndrome, refractory endometrium), conditions that prevent correct ultrasound assessment (tilted uterus), or a history of recurrent implantation failure or repeated miscarriages.DiscussionThe findings from this study will provide valuable insights into the potential influence of the “endometrial compaction” phenomenon on reproductive outcomes during natural cycle endometrial preparation. By examining this aspect, we aim to contribute to a better understanding of the factors that may impact successful outcomes in fertility treatments.

Introduction: The relationships between the outcome of frozen-thaw embryo transfer (FET) cycle and endometrial compaction were not quite consistent. Objective: To analyze the relationship between the outcome of FET cycle and endometrial compaction. Materials and methods: A total of 1420 women using FET were researched. The change in endometrial thickness on ET day and those on the day of progesterone (P) administration start is the basis for grouping. Group 1 was endometrial compaction group, and group 2 was the endometrial non-compaction group. Outcome measure was clinical pregnancy, estradiol (E2) levels, progesterone (P) levels, endometrial morphology, and thickness in each period of FET cycle. Results: A significantly lower clinical pregnancy rate was observed in group 2 in comparison with group 1 (43.4% vs. 55.1%, P < 0.01). In addition, P levels on the day of P administration start were lower in group 2 (0.73 ± 0.93 ng/ml vs. 0.90 ± 1.85 ng/ml, P = 0.006), while E2 levels on ET day were higher in group 2 (316.42 ± 304.95 pg/ml vs. 257.88 ± 219.15 pg/ml, P = 0.001) than in group 1. The binary logistic regression analysis showed a lower rate of clinical pregnancy in group 2 (aOR = 0.617, 95% CI 0.488-0.779, P = 0.001). Conclusions: Clinical pregnancy rates were significantly higher in women with endometrial compaction on ET day compared to women with no changes or thickening. Therefore, we recommend paying closer attention to endometrial compaction in women undergoing FET as a method to estimate endometrial receptivity. [ABSTRACT FROM AUTHOR]

We aimed to assess the effect of endometrial compaction on the live birth rate in frozen-thawed embryo transfer (FET) cycles and to investigate the parameters associated with compaction. FET cycles performed in a tertiary care infertility centre between May 2013 and October 2019 were reviewed retrospectively. The decremental change of endometrial thickness between the end of oestrogen phase and ET day was defined as endometrial compaction. The primary outcome measure was endometrial compaction, and the secondary outcome was the live birth rate. Among all, 89 had endometrial compaction and 194 did not. The live birth rate was significantly higher in the compaction group (23.6 vs. 13.4%, respectively; p = 0.039). Multivariate logistic regression analysis revealed that in FET cycles with artificial endometrial preparation, the chance for live birth was significantly higher in cycles with endometrial compaction [OR: 3.133, 95% confidence interval (CI) 1.104–8.892; p = 0.032] when adjusted for age, stage of the embryo, and endometrial thickness at the end of the oestrogen phase. According to receiver operating characteristic (ROC) curve analysis the sensitivity and specificity of 9.25 mm endometrial thickness at the end of oestrogen phase were 76.4 and 58.8%, respectively (area under the curve: 0.701, 95% CI 0.640–0.763; p < 0.001) to predict endometrial compaction. [ABSTRACT FROM AUTHOR]

Abstract Background This study aims to study whether the change of endometrial thickness between the day of human chorionic gonadotrophin (HCG) administration and the day of embryo transfer (ET) has any effect on ectopic pregnancy (EP) rate following fresh in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles. Methods This study retrospectively analyzed 3134 patients who underwent fresh IVF/ICSI ET, including 3022 intrauterine, 112 ectopic cycles. Multiple logistic regression analysis and stratified analysis were used to study the effect of endometrial compaction after HCG administration on EP in patients with non-thin endometrium after adjusting for confounding factors. Results After adjusting for confounders, multiple logistic regression analysis found that the risk of EP in the compaction group was significantly lower than that in the non-compaction group (OR = 0.49; 95% CI: 0.31–0.78; P = 0.0023). The results of the stratified analysis demonstrated the EP rate in patients with an endometrial thickness ≥ 8 mm on the day of ET; the compaction group significantly reduced the incidence of EP (OR = 0.49; 95% CI: 0.31–0.79; P = 0.0036). In patients with an endometrial thickness ≥ 8 mm on the day of ET, the incidence of EP had no statistical significance in two group (OR = 1.02; 95% CI: 0.18–5.88; P = 9790). Conclusion(s) In patients with non-thin endometrium, endometrial thickness compaction from the day of HCG to the ET day reduced the risk of EP significantly.

Does a decrease in endometrial thickness (compaction ≥10%) before embryo transfer prognosticate the risk for preterm birth and placenta-mediated pregnancy complications among IVF pregnancies? Retrospective cohort study at a large private fertility practice. Patients with a singleton live birth after a fresh or frozen embryo transfer between 2016 and 2019 were included. The primary outcome was preterm birth (delivery before 37 weeks gestational age). Secondary outcomes included gestational hypertension, pre-eclampsia, intrauterine growth restriction and placental abruption. Of the 252 patients that met the study criteria, 122 (48%) demonstrated endometrial compaction (≥10%) and 130 (52%) did not. Age, body mass index (BMI), parity, history of preterm birth or history of pre-existing maternal conditions between the compaction and no-compaction groups were not significantly different. The overall prevalence of placenta-mediated complications across all participants was 25% (n = 62). The number of preterm births between the compaction and no-compaction groups (13% and 6%, respectively, P = 0.09) as well as the prevalence of placenta-mediated complications (29.5% and 20%, respectively, P = 0.08) were not significantly different. Findings for the primary outcome (preterm birth) persisted even after adjustment for potential confounding variables, including maternal age, parity, BMI, embryo score and type of embryo transfer (fresh versus frozen) (adjusted OR 1.86, 95% CI 0.64 to 5.38). Endometrial compaction (or decrease in endometrial thickness) before embryo transfer is not associated with preterm birth or placenta-mediated pregnancy complications. [ABSTRACT FROM AUTHOR]

Objective: The aim of our study was to evaluate sonographic endometrial thickness succeeding the estrogen-only stage and on the day when embryo transfer (ET) occurred in artificial frozen embryo transfer (FET) cycles to delve into the effect of endometrial compaction (EC) on clinical pregnancy rate (CPR). Patients and Methods: In the first group endometrial thickness diminished when ET occurred when compared to the end of the estrogen-only phase (n:37). Endometrial thickness increased/did not alter for the second group (n:70). Demographic characteristics were recorded and the following were studied: in vitro fertilization (IVF) treatment indications, hormone levels, total antral follicle count, duration of infertility, embryo quality, embryo-fundus distance, endometrial thickness at the end of estrogen-only phase and on ET day, luteal support, CPR. Results: No significant difference occurred in CPRs (n:107). ET, on day 5 was higher in the first group (p<0.05). Regression analysis revealed EC was 8.000 times higher in those with ET day 5 than those with 3. CONCLUSION: Endometrial compaction is non-relevant to the rate of clinical pregnancy. The day of ET affected the presence of EC. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Compression/thinning of the endometrial thickness with the effect of progesterone during the luteal phase of the menstrual cycle is defined as endometrial compaction. This study aimed to show the effect of changes in endometrial thickness in the luteal phase of intrauterine insemination cycles on pregnancy outcomes. STUDY DESIGN: Fifty-eight patients who were planned for intrauterine insemination were included in this prospective cohort study. The effect of the change between the patients' endometrial measurements on the day of trigger and the 7th day after intrauterine insemination on pregnancy outcomes were compared. Patients were divided into 3 groups according to endometrial thickness change. Those with an endometrial thickness change of less than 5% were called the no change group (n=18). The groups with endometrial thickness decreasing more than 5% (n=9) and increasing (n=31) formed the other two groups. In addition, the effect of luteal phase support on endometrial compaction was investigated. RESULTS: The highest pregnancy rate (55.6%) was observed in the group with more than 5% endometrial thinning. It was found to be 16.7% in the group without change and 19.4% in the group with an increased endometrial thickness (p=0.045). endometrial compaction and pregnancy rates were higher in the group given oral dydrogesterone for luteal support compared to those using vaginal micronized progesterone. CONCLUSION: Endometrial compaction increases clinical pregnancy in intrauterine insemination cycles. Further studies are necessary to confirm the results of this study. [ABSTRACT FROM AUTHOR]

Background: This study aims to study whether the change of endometrial thickness between the day of human chorionic gonadotrophin (HCG) administration and the day of embryo transfer (ET) has any effect on ectopic pregnancy (EP) rate following fresh in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles. Methods: This study retrospectively analyzed 3134 patients who underwent fresh IVF/ICSI ET, including 3022 intrauterine, 112 ectopic cycles. Multiple logistic regression analysis and stratified analysis were used to study the effect of endometrial compaction after HCG administration on EP in patients with non-thin endometrium after adjusting for confounding factors. Results: After adjusting for confounders, multiple logistic regression analysis found that the risk of EP in the compaction group was significantly lower than that in the non-compaction group (OR = 0.49; 95% CI: 0.31–0.78; P = 0.0023). The results of the stratified analysis demonstrated the EP rate in patients with an endometrial thickness ≥ 8 mm on the day of ET; the compaction group significantly reduced the incidence of EP (OR = 0.49; 95% CI: 0.31–0.79; P = 0.0036). In patients with an endometrial thickness ≥ 8 mm on the day of ET, the incidence of EP had no statistical significance in two group (OR = 1.02; 95% CI: 0.18–5.88; P = 9790). Conclusion(s): In patients with non-thin endometrium, endometrial thickness compaction from the day of HCG to the ET day reduced the risk of EP significantly. [ABSTRACT FROM AUTHOR]

Does endometrial compaction, determined by both transvaginal (TVUS) and abdominal ultrasonography (AUS), improve reproductive outcomes in vitrified–warmed embryo transfer (FET) cycles, and is there a correlation between compaction and serum progesterone concentrations on day of embryo transfer? Prospective observational cohort study at a single tertiary care IVF centre including 204 patients undergoing high-quality vitrified–warmed blastocyst transfer in a hormone replacement therapy (HRT) cycle. The change in endometrial thickness (EMT) between end of oestrogen-only phase and day of embryo transfer, as measured by sequential TVUS, was used to categorize endometrium as undergoing compaction (≥5% decrease), no change, or expansion (≥5% increase). EMT was also examined using AUS at the time of embryo transfer. Primary outcome measure was ongoing pregnancy rates. Thirty-one cycles (15.2%) demonstrated compaction, whereas 123 (60.3%) expanded and 50 (24.5%) remained unchanged as measured by sequential TVUS. Ongoing pregnancy rates did not differ among cycles with compaction (58.1%), those with expansion (56.9%), and those with no change (60.0%; P =0.932). Furthermore, oestrogen, progesterone and oestrogen/progesterone concentrations on day of embryo transfer were comparable among all groups. Using AUS, endometrial compaction was seen in 46 cycles (22.5%), and there was a positive correlation between body mass index and AUS-measured EMT change (ρ = 0.161, P = 0.021). In the group with AUS-determined endometrial compaction, AUS measurements showed a significantly thinner EMT on day of embryo transfer (8.3 mm; interquartile range [IQR] [7.5; 9.2] versus 9.3 mm; IQR [8.4; 11.4], P < 0.001) and higher for EMT change (1.3 mm; IQR [0.8; 1.7] versus 0.1 mm; IQR [–1.1; 1.0], P < 0.001) compared with TVUS measurements. Endometrial compaction during HRT–FET does not predict ongoing pregnancy. [ABSTRACT FROM AUTHOR]

Study Question: Is there a relationship between endometrial compaction and live birth in euploid frozen embryo transfer (FET) cycles?Summary Answer: Live birth rates (LBRs) were similar in both patients that demonstrated endometrial compaction or no compaction in single euploid FETs.What Is Known Already: There has been increasing interest in the correlation between endometrial compaction and clinical outcomes but there has been conflicting evidence from prior investigations.Study Design, Size, Duration: This was a prospective observational study from 1 September 2020 to 9 April 2021.Participants/materials, Setting, Methods: This study was performed at a single, academically affiliated fertility center in which patients who had an autologous single euploid FET using a programmed or modified natural cycle protocol were included. All embryos had trophectoderm biopsy for preimplantation genetic testing for aneuploidy followed by vitrification at the blastocyst stage. Two ultrasound measurements of endometrial thickness (EMT) were obtained. The first measurement (T1) was measured transvaginally within 1 day of initiation of progesterone or ovulation trigger injection, and a second EMT (T2) was measured transabdominally at the time of embryo transfer (ET). The primary outcome (LBR) was based on the presence and proportion of compaction (percentage difference in EMT between T1 and T2).Main Results and the Role Of Chance: Of the 186 participants included, 54%, 45%, 35%, 28% and 21% of women exhibited >0%, ≥5%, ≥10%, ≥15% and ≥20% endometrial compaction, respectively. Endometrial compaction was not predictive of live birth at any of the defined cutoffs. A sub-analysis stratified by FET protocol type (n = 89 programmed; n = 97 modified natural) showed similar results.Limitations, Reasons For Caution: There was the potential for measurement error in the recorded EMTs. The T2 measurement was performed transabdominally, which may cause potential measurement error, as it is generally accepted that transvaginal measurements of EMT are more accurate, though, any bias is expected to be non-differential. The sub-analysis performed looking at FET protocol type was underpowered and should be interpreted with caution. Our study, however, represents a pragmatic approach, as it allowed patients to avoid having to come in for an extra transvaginal ultrasound the day before or on the day of ET.Wider Implications Of the Findings: Assessing endometrial compaction may lead to unnecessary cycle cancellation. However, further studies are needed to determine if routine screening for endometrial compaction would improve clinical outcomes.Study Funding/competing Interest(s): No authors report conflicts of interest or disclosures. There was no study funding.Trial Registration Number: NCT04330066. [ABSTRACT FROM AUTHOR]

Purpose: To determine if the change in endometrial thickness following exogenous progesterone (P) initiation correlates with outcome following autologous transfer of a single thawed blastocyst. Methods: The study is a retrospective observational cohort study conducted at a private fertility center. Patients scheduled for thawed blastocyst transfer received artificial endometrial preparation (artificial cycle FET) and underwent serial ultrasonography. The main outcomes were the rate of ongoing pregnancy (fetal heart motion at 12 weeks of gestation) and early pregnancy loss. Logistic regression was used to test for correlations between these outcomes and the change in endometrial thickness while adjusting for potential confounders (patient age, embryo quality, and the use of genetic testing). Results: There were 232 qualifying autologous single-blastocyst transfers in the 20-month study period ending 31 December 2019. Mean endometrial thicknesses were 3.8 mm, 10.0 mm, and 11.2 mm at baseline, P initiation, and at transfer, respectively. The change in endometrial thickness after exogenous P exposure ranged from − 5 to + 9 mm and negatively correlated with ongoing pregnancy in logistic regression analyses. Specifically, ongoing pregnancy rates per transfer were 63.2% in 19 cases where endometria compacted by 10% or more, 64.2% in 95 cases where there was unchanged endometrial thickness, and 52.5% in 118 cases where endometria expanded. Conclusions: The change in endometrial thickness after P initiation was associated with the probability of ongoing pregnancy but not with early pregnancy loss. Ongoing pregnancy rates were greater in endometria with negative growth (compaction) when compared to endometria that grew (expanded) after P exposure. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate whether endometrial compaction using sequential transvaginal ultrasound is associated with improved live birth rates in medicated single euploid frozen embryo transfer (FET) cycles. Methods: Prospective observational cohort study at a private fertility clinic. Patients who underwent FETs between January and December 2018 were assessed for inclusion. The change in endometrial thickness between the end of the estrogen phase and the day before embryo transfer, measured by sequential transvaginal ultrasound, was used to categorize cycles with compaction (≥ 5%), no change, or expansion (≥ 5%). FET cycle outcomes were then compared between groups. The primary outcome was live birth. Secondary outcomes include clinical pregnancy rate and rate of spontaneous abortion. Results: Of the 259 single euploid medicated FETs performed during the study period, only 43/259 (16.6%) of the cycles demonstrated ≥ 5% compaction, whereas 152/259 (58.7%) expanded and 64/259 (24.7%) were unchanged. Live birth rates did not differ between cycles with compaction (58.1%), no change (54.7%), or expansion (58.6%), p = 0.96. Clinical pregnancy and spontaneous abortion rates were also similar between groups. Conclusion: The vast majority of cycles did not demonstrate endometrial compaction. Endometrial compaction is not associated with live birth rate or spontaneous abortion rate in medicated single euploid FETs in this cohort. [ABSTRACT FROM AUTHOR]