Pregnancy prediction via ultrasound-detected endometrial blood for hormone replacement therapy-frozen embryo transfer: a prospective observational study

Pregnancy prediction via ultrasound-detected endometrial blood for hormone replacement therapy-frozen embryo transfer: a prospective observational study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Pregnancy prediction via ultrasound-detected endometrial blood for hormone replacement therapy-frozen embryo transfer: a prospective observational study Xue Ke, Xue-fei Liang, Yong-hong Lin, Fang Wang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3257917/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 24 Nov, 2023 Read the published version in Reproductive Biology and Endocrinology → Version 1 posted 12 You are reading this latest preprint version Abstract Background This study aimed to assess the predictive value of endometrial blood flow branches on pregnancy outcomes after hormone replacement therapy-frozen embryo transfer (HRT-FET). Methods This prospective observational study involved 174 reproductive-aged women who underwent endometrial receptivity assessment in a tertiary care academic medical center in southwest China using power Doppler ultrasonography during HRT-FET. On the day of endometrial transformation and the day before embryo transfer, three-dimensional power Doppler ultrasound was performed. The endometrial blood flow branches of endometrial and subendometrial regions were compared in non-pregnant and pregnant groups at the two time points above. Results The endometrial blood flow branches were higher in pregnant patients than in non-pregnant patients on the day of endometrial transformation (P = 0.025) and the day before embryo transfer (P = 0.009). Changes in endometrial blood flow pattern and endometrial blood flow branches at the two time points did not differ among the pregnancy outcome samples. After adjusting for age, antral follicles, and embryos transferred, the endometrial blood flow branches on the day before embryo transfer was the independent factor influencing the chance of clinical pregnancy, with an odds ratio of 2.745 (95% confidence interval: 1.054–7.153, P = 0.039). Conclusions Endometrial blood flow perfusion during the peri-transplantation period of the HRT-FET cycle is a good indicator of pregnancy outcomes, suggesting that valuation of endometrial branches via power Doppler ultrasound is a simple and effective approach for achieving indicator measurements. Power Doppler ultrasound endometrial receptivity endometrial blood flow frozen embryo transfer Figures Figure 1 Background Accurate assessment of endometrial development and receptivity remains a challenge in reproductive medicine. None of the endometrial receptivity markers that are able to be evaluated by endometrial biopsy, endometrial fluid aspiration, or hysteroscopy have sufficient discriminatory value to act as a diagnostic measure for endometrial receptivity [ 1 ]. However, ultrasound remains the most non-invasive and reproducible method for evaluating endometrial receptivity compared to invasive methods, such as histology and molecular research. Previous studies have focused on the effects of independent ultrasound parameters on embryo implantation, including endometrial patterns and thickness, which have been repeatedly tested and compared with pregnancy rates during in vitro fertilization (IVF) cycles with conflicting results [ 2 , 3 ]. In recent years, some studies have focused on the comprehensive evaluation of ultrasound parameters for predicting endometrial receptivity, including conservative endometrial measurements, endometrial myometrial junction studies, and comprehensive scores of endometrial and subendometrial Doppler indices [ 4 , 5 ], which are considered to better represent the true ability of the endometrium to accept embryos. Among the various ultrasound parameters, endometrial blood flow perfusion is typically considered a necessary condition for embryo implantation. This factor can be non-invasively evaluated and roughly estimated using color Doppler ultrasound; however, power Doppler imaging is more sensitive for detecting low-speed flow, with stronger visibility of small blood vessels, increased accuracy in counting, and high operability [ 6 , 7 ]. Therefore, power Doppler has the potential to become a daily detection tool for checking the blood supply to the entire endometrium and subendometrial area. To the best of our knowledge, research on endometrial blood flow correlating power Doppler ultrasound (PD-US) data with hormone replacement therapy-frozen embryo transfer (HRT-FET) pregnancy outcomes remains rare, and the optimal measurement time for pregnancy outcome prediction remains unclear. Moreover, in the majority of independent or comprehensive parameters used to evaluate endometrial receptivity, the evaluation is often limited to a specific time point, such as oocyte retrieval day and embryo transfer day. In this study, we evaluated the role of endometrial receptivity ultrasound parameters in predicting pregnancy on the day of endometrial transformation and the day before embryo transfer in HRT-FET cycles. At the same time, changes of endometrial and subendometrial blood flow at two time points were added to evaluate the prediction performance. These results may be used to evaluate the value of incorporating appropriate endometrial receptivity indicators into routine monitoring during HRT-FET cycles. Methods Study subjects This prospective observational study was conducted at a tertiary care academic medical center in southwestern China. Women who received their first HRT-FET between November 2021 and January 2023 were invited to participate in this study. Based on previous ultrasound, hysterosalpingography, magnetic resonance imaging, or surgical records, patients with stage III and IV endometriosis, adenomyosis, hydrosalpinx, uterine fibroids, history of severe uterine adhesions, endometrial polyps, scarred uterus, or uterine malformations were excluded. Furthermore, patients with a history of recurrent miscarriage or repeated implantation failure (more than three occurrences) were excluded from the study. This study was approved by the Scientific Ethics Committee of Chengdu Women’s and Children’s Central Hospital (reference: B2021-7), and all enrolled patients provided informed consent. FET procedures For hormonal replacement therapy cycles, all patients received estradiol (Femoston red tablets; Abbott Biologicals B.V., Olst, NL) treatment at 4 mg orally, with the dosage regulated on a 7-day basis according to endometrial thickness (EMT). If the EMT was < 8 mm, the estradiol dosage was increased. When the EMT reached ≥ 8 mm, and the oral estradiol dosage reached ≥ 14 days, or the clinicians and patients recognized EMT as having a relatively maximum thickness, progesterone was administered to initiate endometrial transformation. Secretory transformation was initiated using fematon-yellow tablets (containing estradiol 2 mg and dydrogesterone 10 mg; Abbott Biologicals B.V.) twice daily, and 40 mg oil-based intramuscular progesterone injection (Zhejiang Xianju Pharmaceutical) once daily was administered from the day of transformation to the day of the pregnancy test. Power Doppler operation and data collection Identity 3D power Doppler (3D PD-US, H60, Samsung, Seoul, South Korea) settings with a transvaginal probe of 4 − 9 MHz were used in patients for endometrial receptivity testing on the endometrial transformation day as well as on the day preceding embryo transfer at approximately 1 pm. The settings for this study were as follows: low frequency; signal magnifying, 50; pulse repetition frequency, 0.8 kHz; power Doppler map, 5; and power, 90%. The sector of interest was adjusted to cover the endometrial cavity in the longitudinal plane of the uterus. The color gain was adjusted to 80%±2% to optimize the detection of blood flow in the small vessels of endometrial and subendometrial areas. The data produced by the PD-US measurement included EMT, endometrial patterns (classified as type A, trilinear endometrium; type Not-A, no trilinear endometrium), endometrial contraction, endometrial volume, blood flow patterns (definition from Applebaum [ 8 ]: type I, the vessels pass through the lateral hypo-echoic band of the endometrium but do not enter the hyper-echoic rim of the endometrium; type II, the vessels pass through the hyper-echoic rim of the endometrium but do not enter the endometrium; type III, the vessels enter the endometrium), endometrial blood flow branches (countable endometrial and subendometrial blood flow branches in a single plane) (Fig. 1 ). In this study, the subendometrial region was considered to be within 1 mm of the originally defined myometrial–endometrial contour [ 9 ]. The endometrial volume was drawn manually along the endometrial outline. Stored volumes were analyzed using VOCAL software of Three-dimensional (3D) Power Doppler. The results of the ultrasound evaluation did not affect the subsequent clinical procedures. The primary outcome measure was intrauterine clinical pregnancy( defined as the presence of a gestational sac in the uterus determined using ultrasonography). Statistical analyses Statistical analyses were performed using the Statistical Program for Social Sciences (SPSS Version 26, IBM Corp, Armonk, NY, USA). Normal distribution was identified using the Shapiro-Wilk test. All results are presented as medians and ranges because of the non-normally distributed data. Satistical comparison was performed using the Mann − Whitney U test, chi-squared and Fisher’s Exact tests, where appropriate. Binary stepwise logistic regression was used to determine the independent predictive factor of clinical pregnancy, adjusting for patient age, antral follicles (AFC), number of embryos transferred, embryo transfer type, good quality embryos transfer, endometrial blood flow, and changes of blood flow at two time points. The results are presented as the odds ratio (OR) and 95% confidence interval (CI). The significance level for all analyses was set at P < .05. Results A total of 174 patients who underwent HRT-FET met the inclusion criteria and were processed for this study and completed PD-US tests on the day of endometrial transformation and the day before embryo transfer. Among them, 101 patients achieved clinical pregnancy, including one who had a tubal pregnancy (1/101) and six who had spontaneous abortions (6/101). The remaining 73 patients were classified into the non-pregnant group, with a intrauterine pregnancy rate of 57.47% per HRT-FET. The demographic and clinical characteristics of the patients are presented in Table 1. Table 1. Demographic and clinical characteristics of pregnant and non-pregnant patients undergoing HRT-FET Characteristic Pregnant group Non-pregnant group P-value No. of patients 101 73 --- Age (years) a 32.0 (29.0−34.0) 33.0（30.0-37.0） 0.011 BMI (kg/m 2 ) a 22.0 (20.0−23.70) 22.7 (20.75−23.75) 0.309 AMH (ng/mL) b 3.28 (1.815−6.90) 2.93(1.575−5.15) 0.113 AFC a 12.0 (8.0−18.5) 10.0 (6.0−14.5) 0.010 Primary infertility (n, %) 51 (50.5) 35 (47.9) 0.74 Cause of infertility (n, %) 0.369 Tubal 77 (76.24) 61 (83.56) Aovulatory 6 (5.94) 1 (1.37) DOR 10 (9.9) 9 (12.30) Endometriosis Male 2 (1.98) 0 (0.00) Unexplained 1 (1.00) 0 (0.00) Male factor 5 (4.95) 2 (2.74) No. of embryos transferred 2.0 (1.0−2.0) 1.0 (1.0−2.0) 0.123 Blastocysts transfer cycles (n, %) 58 (57.43) 35 (47.9) 0.216 Good quality embryos transfer cycles (n, %) 81 (80.20) 54 (73.97) 0.331 Abbreviations: BMI body mass index; AMH anti-Müllerian hormone; AFC antral follicle; DOR Decreased ovarian reserve. Comparison of characteristics between pregnant and non-pregnant patients There was a significant difference in age distribution between the pregnancy and non-pregnancy groups (32.0 [29.0−34.0] years vs. 33.0 [30.0−37.0] years; P=0.011) as well as a significant difference in bilateral AFC between the two groups (12.0 [8.0−18.5] vs. 10.0 [6.0−14.5]; P=0.010). However, both groups did not show significant differences in body mass index, anti-Müllerian hormone levels, the proportion of primary infertility, and the cause of infertility. The fallopian tube was the most common infertility factor in both groups. The proportion of blastocyst transfer cycles (57.43% vs. 47.9%) and good-quality embryo transfer cycles (80.20% vs. 73.97%) was higher in the pregnancy group than in the non-pregnancy group, but without significant difference (Table 1). Endometrial receptivity indices on the day of endometrial transformation and the day before embryo transfer Table 2 summarizes the endometrial PD-US indices on the days of endometrial transformation and before transplantation. On the day of endometrial transformation, there were significant differences in blood flow branches among the different clinical pregnancy outcome samples (P=0.025). On the day before transplantation, endometrial blood flow branches were found to be higher in pregnant patients than in non-pregnant patients (P=0.009). However, both groups were similar in terms of EMT, frequency or direction of endometrial contraction, endometrial blood flow pattern, and endometrial volume at the two time points. All five patients with endometrial blood flow branches ≥10 on the day of secretory transformation were pregnant. Meanwhile, there were six patients with endometrial blood flow branches >10 on the day before transplantation, five were pregnant, and the remaining one who was not pregnant was transplanted with a D6 poor-quality blastocyst. Table 2. Comparison of endometrial receptivity of 3D power Doppler indices on the day of endometrial transformation and the day before embryo transfer between pregnant and non-pregnant patients Parameter endometrial transformation day P-value the day before embryo transfer P-value Pregnant Non-pregnant group Pregnant Non-pregnant No. of patients 101 73 —— 101 73 —— EMT (mm) 9.5 (8.0−11.0) 9.5 (8.0−11.25) 0.599 9.0 (8.5−11.0) 9.5 (8.0−11.0) 0.876 EMP (n,%) 0.156 0.366 A 86 (85.15) 56 (76.71) 6 (5.94) 7 (9.59) N-A 15 (14.85) 17 (23.29) 95 (94.06) 66 (9.04) FEC ,n 3.0 (2.0−5.0) 3.0 (2.0−4.0) 0.244 2.0 (1.0−3.0) 2.0 (1.0−3.0) 0.994 DEC (n,%) 0.723 0.756 two-way 82 (81.19) 59 (80.82) 78 (97.50) 57 (96.61) forward 8 (7.92) 7 (9.59) 2 (2.50) 2 (3.39) reverse 5 (4.95) 2 (2.74) 0 (0.00) 0 (0.00) EMBLP (n,%) 0.873 0.738 Type I 7 (6.93) 4 (5.48) 11 (10.89) 10(13.70) Type II 45 (44.55) 32 (43.84) 46 (45.54) 35 (47.95) Type III 49 (48.51) 37 (50.68) 44 (43.56) 28 (38.36) EMBLB (n,%) 0.025 0.009 <5 38 (37.62)（37.62%） 40 (54.79) 34 (33.66) 39 (43.43) ≥5 63 (62.38) 33 (45.21) 67 (66.34) 34 (46.58) EV (cm 3 ) 2.76(2.07−3.97) 2.96 (2.31−3.74) 0.682 3.20 (2.37−4.40) 3.20 (2.43−4.04) 0.663 Forward: Cervico-to-fundal movement. Reverse: fundal-to-cervical movement. Abbreviations: EMT endometrial thickness; EMP endometrial pattern; FEC frequency of endometrial contraction; DEC direction of endometrial contraction; EMBLP endometrial blood flow pattern; EMBLB endometrial blood flow branches; EV endometrial volume. Changes in endometrial blood flow parameters It was found that different pregnancy outcome samples did not show significant differences in the changes in endometrial blood flow and blood flow branch between the day of progesterone initiation and the day before FET (Table 3). Table 3. Comparison of changes in endometrial blood flow indices from the day of progesterone administration to the day before embryo transfer between pregnant and non-pregnant patients parameters Pregnant group Non-pregnant group P -value Number of patients 101 73 --- Change in EMBLP (n, %) 0.671 N-Change 83 (82.18) 60（82.19） I-II 2 (1.98) 3(4.11) II-III 16 (15.84) 10（13.70） Change in EMBLB(n, %) 0.398 N-Change 84 (83.17) 57 (78.08) Increasement 17 (16.83) 16 (21.92) N-Change: no significant change in parameters at two time points Increment: blood flow branches from <5 on the day of transformation to ≥5 on the day before transfer Abbreviations: EMBLP, endometrial blood flow pattern; EMBLB, endometrial blood flow branches Logistic regression and receiver operating characteristics curve analysis Binary stepwise logistic regression analysis was performed to identify the covariates independently associated with the primary outcome of clinical pregnancy (Table 4). After adjusting for age, AFC, number of embryos transferred, embryo level, the proportion of good-quality embryo transfer, endometrial type, and endometrial blood flow branches, and changes of blood flow at two time points, only the endometrial blood flow branches on the day before embryo transfer significantly improved the chance of pregnancy, with ORs of 2.745 (95% CI: 1.054−7.153, P=0.039). Table 4. Logistic regression analysis to identify covariates independently associated with the clinical pregnancy Covariates Logistic regression coefficient (B) Adjusted OR (95% CI) P - value Age -0.066 0.936 (0.857−1.023) 0.144 AFC 0.032 1.033 (0.978−1.090) 0.246 No. of embryos transferred 0.733 2.080 (0.962−4.498) 0.063 Blastocysts transfer e NO Ref. YES 0.674 1.963 (0.884−4.358) 0.098 Good quality embryo transfer NO Ref. YES 0.029 1.030 (0.462−2.295) 0.943 EMBLB on the endometrial transformation day <5 Ref. ≥5 0.114 1.121 (0.464−2.707) 0.800 EMBLB on the day before embryo transfer <5 Ref. ≥5 1.010 2.745 (1.054−7.153) 0.039 Change in EMBLB N-Change Ref. Increment 0.851 2.343 (0.721−7.608) 0.157 Abbreviations: AFC antral follicle; EMBLB endometrial blood flow branches; OR odds ratio; CI confidence interval. Discussion The results of this study demonstrated that measuring the endometrial blood perfusion using PD-US was shown to be a simple and effective method for predicting pregnancy outcomes during the HRT-FET cycle. Embryos are estimated to account for one-third of implantation failures, whereas poor endometrial receptivity and altered embryo endometrial dialogue account for the remaining two-thirds [10]. Several studies have examined EMT, endometrial type, subendometrial contraction, and endometrial volume and have attempted to provide a clear overview of the implantation window. However, contradictory findings have been reported [11,12]. The above-mentioned ultrasound endometrial indicators were not the final factors affecting pregnancy outcomes in our study. This study evaluated the role of PD-US in predicting pregnancy during HRT-FET cycles by counting endometrial and subendometrial blood flow branches. The pregnant group was younger and had higher AFC values. However, after adjusting for these parameters, the branches of the spiral arteries on the day before transplantation were the only factors that affected pregnancy outcomes. While Wang et al. concluded that the coexistence of endometrial and subendometrial blood flow results in a higher embryo implantation rate [13], our results suggest that blood perfusion is more important than the endometrial−subendometrial blood flow distribution pattern. Blood supply to the endometrium comes from the radial artery, which passes through the connection between the uterine muscle and endometrium, divides into basal arteries that supply the basal layer, and then forms a spiral artery to reach the surface of the endometrium. At the junction of the myometrium and endometrium, ultrasonography shows a low-echo area called the subendometrial area. Histological studies have confirmed that this area is the innermost layer of the myometrium, or the junction zone [14]. Compared to the outer muscular layer, our results showed that blood flow in the junction zone was more abundant in most cases. Thus, whether the branch enters the endometrium the day before embryo transfer may not be an absolute factor affecting pregnancy outcomes; rather, the richness of blood flow in the endometrium or junction zone is suggested as a predictive factor. In this study, all five patients with endometrial blood flow branches >10 on the progesterone start day were pregnant, while five with blood flow branches >10 on the day before transplantation had conceived. Therefore, we emphasize the possible positive relationship between the abundance of blood flow during the secretory phase and pregnancy; however, it should not be concluded that patients without endometrial or subendometrial blood flow branches have absolutely low implantation and pregnancy rates. In patients with blood flow branch counts of 0−1 on either the day of transformation or the day before transplantation, we did not find a linear correlation between no blood flow and pregnancy. These data indicate that there may be a certain threshold for endometrial vascularization, that, when reached, has a significant positive impact on clinical pregnancy. Whether the research conclusions can become a reference option for selective embryo transfer or guide clinical medication requires further large-scale prospective cohort studies. Ng et al. [15] reported that the measurement of endometrial and subendometrial blood flow using 3D PD-US could not predict pregnancy well if measured at a time point during IVF treatment. Due to baseline differences between patients in the present study, we compared the changes in 3D PD-US parameters of the endometrium at the two time points. However, we failed to confirm that the changes on the day of endometrial transformation and the day before embryo transfer were significantly different between the pregnant and non-pregnant groups. It has not been confirmed whether this change has any role in predicting HRT-FET results, and the main variable determining pregnancy outcomes is endometrial blood flow during the peri-transplantation period. This study had the advantage of being the first prospective cohort study to use PD-US to detect endometrial receptive ultrasound indicators at two time points after HRT-FET. Due to the inconsistent Doppler signal waveforms of these small spiral vessels, predicting pregnancy using the spiral artery Doppler flow index is highly controversial [16-18]; thus, our study did not measure the subendometrial vascularization flow index but instead chose a more intuitive indicator for assessing blood perfusion. Previous studies have reported that blood flow to the endometrium affects pregnancy outcomes after freeze-thawed embryo transfer. However, the detection methods were not consistent. Jinno et al. [19] measured endometrial tissue blood flow (ETBF) using laser blood flowmetry and found that women with an endometrial microvascular blood flow of at least 29 mL/min per 100 g of tissue in the early luteal phase had a significantly higher pregnancy rate, with 85% of gestational sacs in normal uteri implanted in the uterine regions with the highest measured ETBF. Other studies have demonstrated that the levels of vascular endothelial growth factor and its receptors significantly increase during the peri-implantation period [20-22]. Additionally, 3D Doppler angiography has been shown to quantitatively evaluate vascular density and blood flow in the endometrium and subendometrium [23]. However, none of these methods have the operability of real-time monitoring during endometrial preparation for FET, whereas 3D PD-US can achieve the convenience of bedside monitoring. There was a limitation to the current study. Most patients refused to undergo transvaginal ultrasound on the day of embryo transfer. Therefore, after endometrial transformation, we performed a second endometrial receptivity test in the afternoon before transplantation, and there may have been some deviations from the actual values on the day of transplantation. Conclusion Measuring the endometrial and subendometrial blood flow branches on the day of the peri-transplantation period during the HRT-FET cycle using PD-US was shown to be a simple and effective method for predicting pregnancy outcomes. In the future, the development of ultrasound may improve the consistency of endometrial blood flow assessment and generate more accurate non-invasive blood flow assessment methods for daily clinical practice, such as microvascular flow ultrasound. Abbreviations HRT-FET hormone replacement therapy-frozen embryo transfer IVF in vitro fertilization PD-US power Doppler ultrasound EMT endometrial thickness AFC antral follicles OR odd ratio CI confidence interval 3D three-dimensional ETBF endometrial tissue blood flow EMP endometrial pattern FEC frequency of endometrial contraction DEC direction of endometrial contraction EMBLP endometrial blood flow pattern EMBLB endometrial blood flow branches EV endometrial volume Declarations Ethics approval and consent to participate This study was approved by the Scientific Ethics Committee of Chengdu Women’s and Children’s Central Hospital (reference: B2021-7), and all enrolled patients provided informed consent. Consent for publication Not applicable. Availability of data and materials Not applicable. Competing interest The authors report no conflict of interest for this work. Funding The authors declare that no funds, grants, or other support were received during the preparation of this manuscript. Authors’ contributions Xue Ke conducted the data analyses and manuscript drafting. XF Liang contributed to the data collection. YH Lin and Fang Wang were responsible for the interpretation of the data and revision of the article. All authors critically reviewed and approved the final version of the article. Acknowledgments We would like to thank the staff of the Department of Assisted Reproduction at Chengdu Women’s and Children’s Central Hospital for their cooperation and support. References Craciunas L, Gallos I, Chu J, Bourne T, Quenby S, Brosens JJ, et al. Conventional and modern markers of endometrial receptivity: a systematic review and meta-analysis. Hum Reprod Update. 2019;25:202-23. Liu WJ, Nong YQ, Ruan JX, Chen Y, Fan L, Huang QW, et al. 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Cite Share Download PDF Status: Published Journal Publication published 24 Nov, 2023 Read the published version in Reproductive Biology and Endocrinology → Version 1 posted Editorial decision: Major revision 27 Sep, 2023 Reviews received at journal 26 Sep, 2023 Reviewers agreed at journal 15 Sep, 2023 Reviewers agreed at journal 02 Sep, 2023 Reviewers agreed at journal 30 Aug, 2023 Reviews received at journal 23 Aug, 2023 Reviewers agreed at journal 19 Aug, 2023 Reviewers agreed at journal 19 Aug, 2023 Reviewers invited by journal 18 Aug, 2023 Editor assigned by journal 14 Aug, 2023 Submission checks completed at journal 14 Aug, 2023 First submitted to journal 12 Aug, 2023 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3257917","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":226298066,"identity":"c1c689d2-e146-4fc2-bc94-a3c4c72d8cd3","order_by":0,"name":"Xue Ke","email":"","orcid":"","institution":"Chengdu Women’s and Children’s Central Hospital, University of Electronic Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Xue","middleName":"","lastName":"Ke","suffix":""},{"id":226298068,"identity":"b255081b-2b3d-41ec-b680-b75816aeb10f","order_by":1,"name":"Xue-fei Liang","email":"","orcid":"","institution":"Chengdu Women’s and Children’s Central Hospital, University of Electronic Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Xue-fei","middleName":"","lastName":"Liang","suffix":""},{"id":226298070,"identity":"53fcebfc-9f0b-4810-bdce-0bbb900fab11","order_by":2,"name":"Yong-hong Lin","email":"","orcid":"","institution":"Chengdu Women’s and Children’s Central Hospital, University of Electronic Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Yong-hong","middleName":"","lastName":"Lin","suffix":""},{"id":226298072,"identity":"c1a13d75-ae94-4cb8-814a-fae4e23b1d2a","order_by":3,"name":"Fang Wang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA5klEQVRIiWNgGAWjYLCCCgZmOTb25oMPEipqiNRyhoHZmJ/nWLLBgzPHiNeSOHNGjpnkwxZmwqoNjp89/OJAjTXjhgMJZhWJDWwM/O3dCfi1nMlLszhwLJ3Z4MCBtBuJO2QYJM6c3YBXi9mBHDPjjw2H2QwONhy7kXiGjcFAIpeAlvNvzICqD/MYHGZsK0hsYyZCy40c4wdALRKSbcxsDERpsb/xxowB6BcDfh42ZomEM8d4CPpFsj/H+AMwxOrb5N9//PijokaOv70XvxYgYJNA5vEQUg4CzB+IUTUKRsEoGAUjGAAAvD9RTg4MFjQAAAAASUVORK5CYII=","orcid":"","institution":"Chengdu Women’s and Children’s Central Hospital, University of Electronic Science and Technology of China","correspondingAuthor":true,"prefix":"","firstName":"Fang","middleName":"","lastName":"Wang","suffix":""}],"badges":[],"createdAt":"2023-08-12 10:29:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3257917/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3257917/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12958-023-01164-9","type":"published","date":"2023-11-24T15:01:12+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":41774881,"identity":"8d96d246-588d-425b-b080-d40fc7a18b03","added_by":"auto","created_at":"2023-08-18 15:40:59","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":3341003,"visible":true,"origin":"","legend":"\u003cp\u003ePower Doppler ultrasound imaging of endometrial and subendometrial blood flow: type-branch\u003c/p\u003e\n\u003cp\u003e(A) type I - branch＜5: the vessels pass through the lateral hypo-echoic band of the endometrium but do not enter the hyper-echoic rim of the endometrium, branch 1\u003c/p\u003e\n\u003cp\u003e(B) type II - branch＜5: the vessels pass through the hyper-echoic rim of the endometrium but do not enter the endometrium, branch 4\u003c/p\u003e\n\u003cp\u003e(C) type III – branch ＜5: the vessels enter the endometrium, branch 4-5\u003c/p\u003e","description":"","filename":"Fig.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3257917/v1/1ff53c421e3b23d685ab47ec.jpg"},{"id":47146610,"identity":"8b289483-c676-424e-b35e-b1e6e903d48e","added_by":"auto","created_at":"2023-11-27 15:08:51","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":520258,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3257917/v1/8a5da3fb-4a03-41c3-9620-df40c748b1b4.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Pregnancy prediction via ultrasound-detected endometrial blood for hormone replacement therapy-frozen embryo transfer: a prospective observational study","fulltext":[{"header":"Background","content":"\u003cp\u003eAccurate assessment of endometrial development and receptivity remains a challenge in reproductive medicine. None of the endometrial receptivity markers that are able to be evaluated by endometrial biopsy, endometrial fluid aspiration, or hysteroscopy have sufficient discriminatory value to act as a diagnostic measure for endometrial receptivity [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. However, ultrasound remains the most non-invasive and reproducible method for evaluating endometrial receptivity compared to invasive methods, such as histology and molecular research. Previous studies have focused on the effects of independent ultrasound parameters on embryo implantation, including endometrial patterns and thickness, which have been repeatedly tested and compared with pregnancy rates during in vitro fertilization (IVF) cycles with conflicting results [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. In recent years, some studies have focused on the comprehensive evaluation of ultrasound parameters for predicting endometrial receptivity, including conservative endometrial measurements, endometrial myometrial junction studies, and comprehensive scores of endometrial and subendometrial Doppler indices [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], which are considered to better represent the true ability of the endometrium to accept embryos.\u003c/p\u003e \u003cp\u003eAmong the various ultrasound parameters, endometrial blood flow perfusion is typically considered a necessary condition for embryo implantation. This factor can be non-invasively evaluated and roughly estimated using color Doppler ultrasound; however, power Doppler imaging is more sensitive for detecting low-speed flow, with stronger visibility of small blood vessels, increased accuracy in counting, and high operability [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Therefore, power Doppler has the potential to become a daily detection tool for checking the blood supply to the entire endometrium and subendometrial area.\u003c/p\u003e \u003cp\u003eTo the best of our knowledge, research on endometrial blood flow correlating power Doppler ultrasound (PD-US) data with hormone replacement therapy-frozen embryo transfer (HRT-FET) pregnancy outcomes remains rare, and the optimal measurement time for pregnancy outcome prediction remains unclear. Moreover, in the majority of independent or comprehensive parameters used to evaluate endometrial receptivity, the evaluation is often limited to a specific time point, such as oocyte retrieval day and embryo transfer day. In this study, we evaluated the role of endometrial receptivity ultrasound parameters in predicting pregnancy on the day of endometrial transformation and the day before embryo transfer in HRT-FET cycles. At the same time, changes of endometrial and subendometrial blood flow at two time points were added to evaluate the prediction performance. These results may be used to evaluate the value of incorporating appropriate endometrial receptivity indicators into routine monitoring during HRT-FET cycles.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy subjects\u003c/h2\u003e \u003cp\u003eThis prospective observational study was conducted at a tertiary care academic medical center in southwestern China. Women who received their first HRT-FET between November 2021 and January 2023 were invited to participate in this study. Based on previous ultrasound, hysterosalpingography, magnetic resonance imaging, or surgical records, patients with stage III and IV endometriosis, adenomyosis, hydrosalpinx, uterine fibroids, history of severe uterine adhesions, endometrial polyps, scarred uterus, or uterine malformations were excluded. Furthermore, patients with a history of recurrent miscarriage or repeated implantation failure (more than three occurrences) were excluded from the study. This study was approved by the Scientific Ethics Committee of Chengdu Women\u0026rsquo;s and Children\u0026rsquo;s Central Hospital (reference: B2021-7), and all enrolled patients provided informed consent.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eFET procedures\u003c/h2\u003e \u003cp\u003eFor hormonal replacement therapy cycles, all patients received estradiol (Femoston red tablets; Abbott Biologicals B.V., Olst, NL) treatment at 4 mg orally, with the dosage regulated on a 7-day basis according to endometrial thickness (EMT). If the EMT was \u0026lt;\u0026thinsp;8 mm, the estradiol dosage was increased. When the EMT reached\u0026thinsp;\u0026ge;\u0026thinsp;8 mm, and the oral estradiol dosage reached\u0026thinsp;\u0026ge;\u0026thinsp;14 days, or the clinicians and patients recognized EMT as having a relatively maximum thickness, progesterone was administered to initiate endometrial transformation. Secretory transformation was initiated using fematon-yellow tablets (containing estradiol 2 mg and dydrogesterone 10 mg; Abbott Biologicals B.V.) twice daily, and 40 mg oil-based intramuscular progesterone injection (Zhejiang Xianju Pharmaceutical) once daily was administered from the day of transformation to the day of the pregnancy test.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003ePower Doppler operation and data collection\u003c/h2\u003e \u003cp\u003eIdentity 3D power Doppler (3D PD-US, H60, Samsung, Seoul, South Korea) settings with a transvaginal probe of 4\u0026thinsp;\u0026minus;\u0026thinsp;9 MHz were used in patients for endometrial receptivity testing on the endometrial transformation day as well as on the day preceding embryo transfer at approximately 1 pm. The settings for this study were as follows: low frequency; signal magnifying, 50; pulse repetition frequency, 0.8 kHz; power Doppler map, 5; and power, 90%. The sector of interest was adjusted to cover the endometrial cavity in the longitudinal plane of the uterus. The color gain was adjusted to 80%\u0026plusmn;2% to optimize the detection of blood flow in the small vessels of endometrial and subendometrial areas.\u003c/p\u003e \u003cp\u003eThe data produced by the PD-US measurement included EMT, endometrial patterns (classified as type A, trilinear endometrium; type Not-A, no trilinear endometrium), endometrial contraction, endometrial volume, blood flow patterns (definition from Applebaum [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]: type I, the vessels pass through the lateral hypo-echoic band of the endometrium but do not enter the hyper-echoic rim of the endometrium; type II, the vessels pass through the hyper-echoic rim of the endometrium but do not enter the endometrium; type III, the vessels enter the endometrium), endometrial blood flow branches (countable endometrial and subendometrial blood flow branches in a single plane) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). In this study, the subendometrial region was considered to be within 1 mm of the originally defined myometrial\u0026ndash;endometrial contour [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The endometrial volume was drawn manually along the endometrial outline. Stored volumes were analyzed using VOCAL software of Three-dimensional (3D) Power Doppler. The results of the ultrasound evaluation did not affect the subsequent clinical procedures. The primary outcome measure was intrauterine clinical pregnancy( defined as the presence of a gestational sac in the uterus determined using ultrasonography).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analyses\u003c/h2\u003e \u003cp\u003eStatistical analyses were performed using the Statistical Program for Social Sciences (SPSS Version 26, IBM Corp, Armonk, NY, USA). Normal distribution was identified using the Shapiro-Wilk test. All results are presented as medians and ranges because of the non-normally distributed data. Satistical comparison was performed using the Mann\u0026thinsp;\u0026minus;\u0026thinsp;Whitney U test, chi-squared and Fisher\u0026rsquo;s Exact tests, where appropriate. Binary stepwise logistic regression was used to determine the independent predictive factor of clinical pregnancy, adjusting for patient age, antral follicles (AFC), number of embryos transferred, embryo transfer type, good quality embryos transfer, endometrial blood flow, and changes of blood flow at two time points. The results are presented as the odds ratio (OR) and 95% confidence interval (CI). The significance level for all analyses was set at P\u0026thinsp;\u0026lt;\u0026thinsp;.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eA total of 174 patients who underwent HRT-FET met the inclusion criteria and were processed for this study and completed PD-US tests on the day of endometrial transformation and the day before embryo transfer. Among them, 101 patients achieved clinical pregnancy, including one who had a tubal pregnancy (1/101) and six who had spontaneous abortions (6/101). The remaining 73 patients were classified into the non-pregnant group, with a intrauterine pregnancy rate of 57.47% per HRT-FET. The demographic and clinical characteristics of the patients are presented in Table 1.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1.\u003c/strong\u003e Demographic and clinical characteristics of pregnant and non-pregnant patients undergoing HRT-FET\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"99%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003e\u003cstrong\u003eCharacteristic\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\"\u003e\n \u003cp\u003e\u003cstrong\u003ePregnant group\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\"\u003e\n \u003cp\u003e\u003cstrong\u003eNon-pregnant group\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\"\u003e\n \u003cp\u003e\u003cstrong\u003eP-value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003eNo. of patients\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\"\u003e\n \u003cp\u003e101\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\"\u003e\n \u003cp\u003e73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\"\u003e\n \u003cp\u003e\u003cem\u003e---\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003eAge (years)\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\"\u003e\n \u003cp\u003e32.0 (29.0\u0026minus;34.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\"\u003e\n \u003cp\u003e33.0（30.0-37.0）\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\"\u003e\n \u003cp\u003e0.011\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003eBMI (kg/m\u003csup\u003e2\u003c/sup\u003e)\u003csup\u003e\u0026nbsp;a\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\"\u003e\n \u003cp\u003e22.0 (20.0\u0026minus;23.70)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\"\u003e\n \u003cp\u003e22.7 (20.75\u0026minus;23.75)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\"\u003e\n \u003cp\u003e0.309\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003eAMH (ng/mL)\u003csup\u003e\u0026nbsp;b\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\"\u003e\n \u003cp\u003e3.28 (1.815\u0026minus;6.90)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\"\u003e\n \u003cp\u003e2.93(1.575\u0026minus;5.15)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\"\u003e\n \u003cp\u003e\u0026nbsp;0.113\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003eAFC\u003csup\u003e\u0026nbsp;a\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\"\u003e\n \u003cp\u003e12.0 (8.0\u0026minus;18.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\"\u003e\n \u003cp\u003e10.0 (6.0\u0026minus;14.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\"\u003e\n \u003cp\u003e0.010\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003ePrimary infertility (n, %)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\"\u003e\n \u003cp\u003e51 (50.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\"\u003e\n \u003cp\u003e35 (47.9)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\"\u003e\n \u003cp\u003e0.74\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003eCause of infertility (n, %)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\" valign=\"top\"\u003e\n \u003cp\u003e0.369\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Tubal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\"\u003e\n \u003cp\u003e77 (76.24)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\"\u003e\n \u003cp\u003e61 (83.56)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Aovulatory\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\"\u003e\n \u003cp\u003e6 (5.94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\"\u003e\n \u003cp\u003e1 (1.37)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003eDOR\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\"\u003e\n \u003cp\u003e10 (9.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\"\u003e\n \u003cp\u003e9 (12.30)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Endometriosis\u003c/p\u003e\n \u003cp\u003eMale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\"\u003e\n \u003cp\u003e2 (1.98)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\"\u003e\n \u003cp\u003e0 (0.00)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Unexplained\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\"\u003e\n \u003cp\u003e1 (1.00)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\"\u003e\n \u003cp\u003e0 (0.00)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Male factor\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\"\u003e\n \u003cp\u003e5 (4.95)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\"\u003e\n \u003cp\u003e2 (2.74)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003eNo. of embryos transferred\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\" valign=\"top\"\u003e\n \u003cp\u003e2.0 (1.0\u0026minus;2.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\" valign=\"top\"\u003e\n \u003cp\u003e1.0 (1.0\u0026minus;2.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\"\u003e\n \u003cp\u003e0.123\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003eBlastocysts transfer cycles (n, %) \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\"\u003e\n \u003cp\u003e58 (57.43)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\"\u003e\n \u003cp\u003e35 (47.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\"\u003e\n \u003cp\u003e0.216\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"44.87394957983193%\"\u003e\n \u003cp\u003eGood quality embryos transfer cycles (n, %) \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.352941176470587%\"\u003e\n \u003cp\u003e81 (80.20)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.672268907563026%\"\u003e\n \u003cp\u003e54 (73.97)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.100840336134453%\"\u003e\n \u003cp\u003e0.331\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eAbbreviations:\u0026nbsp;BMI body mass index; AMH anti-M\u0026uuml;llerian hormone; AFC antral follicle; DOR Decreased ovarian reserve.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eComparison of characteristics between pregnant and non-pregnant patients\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThere was a significant difference in age distribution between the pregnancy and non-pregnancy groups (32.0 [29.0\u0026minus;34.0] years\u0026nbsp;vs.\u0026nbsp;33.0 [30.0\u0026minus;37.0] years;\u0026nbsp;P=0.011) as well as a significant difference in bilateral AFC between the two groups (12.0 [8.0\u0026minus;18.5]\u0026nbsp;vs.\u0026nbsp;10.0 [6.0\u0026minus;14.5]; P=0.010). However, both groups did not show significant differences in body mass index, anti-M\u0026uuml;llerian hormone levels, the proportion of primary infertility,\u0026nbsp;and\u0026nbsp;the cause of infertility. The fallopian tube was the most common infertility factor in both groups. The proportion of blastocyst transfer cycles (57.43% vs.\u0026nbsp;47.9%) and good-quality embryo transfer cycles (80.20% vs.\u0026nbsp;73.97%) was higher in the pregnancy group than in the non-pregnancy group, but without significant difference (Table 1).\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eEndometrial receptivity indices on the day of endometrial transformation and the day before embryo transfer\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTable 2 summarizes the endometrial PD-US indices on the days of endometrial transformation and before transplantation. On the day of endometrial transformation, there were significant differences in blood flow branches among the different clinical pregnancy outcome samples (P=0.025). On the day before transplantation, endometrial blood flow branches were found to be higher in pregnant patients than in non-pregnant patients (P=0.009). However, both groups were similar in terms of EMT, frequency or direction of endometrial contraction, endometrial blood flow pattern, and endometrial volume at the two time points. All five patients with endometrial blood flow branches \u0026ge;10 on the day of secretory transformation were pregnant. Meanwhile, there were six patients with endometrial blood flow branches \u0026gt;10 on the day before transplantation, five were pregnant, and the remaining one who was not pregnant was transplanted with a D6 poor-quality blastocyst.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2.\u003c/strong\u003e Comparison of endometrial receptivity of 3D power Doppler indices on the day of endometrial transformation and the day before embryo transfer between pregnant and non-pregnant patients\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"643\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\" rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eParameter\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"31.57076205287714%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003eendometrial transformation day\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003eP-value\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"34.3701399688958%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003ethe day before embryo transfer\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003eP-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.528301886792452%\" valign=\"top\"\u003e\n \u003cp\u003ePregnant\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.58490566037736%\" valign=\"top\"\u003e\n \u003cp\u003eNon-pregnant group\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.235849056603772%\" valign=\"top\"\u003e\n \u003cp\u003ePregnant\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.650943396226417%\" valign=\"top\"\u003e\n \u003cp\u003eNon-pregnant\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003eNo. of patients\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003e101\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\" valign=\"top\"\u003e\n \u003cp\u003e73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\" valign=\"top\"\u003e\n \u003cp\u003e101\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\" valign=\"top\"\u003e\n \u003cp\u003e73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003eEMT (mm)\u003csup\u003e\u0026nbsp;\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003e9.5 (8.0\u0026minus;11.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\"\u003e\n \u003cp\u003e9.5 (8.0\u0026minus;11.25)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e0.599\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\" valign=\"top\"\u003e\n \u003cp\u003e9.0 (8.5\u0026minus;11.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\" valign=\"top\"\u003e\n \u003cp\u003e9.5 (8.0\u0026minus;11.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e0.876\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003eEMP (n,%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e0.156\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e0.366\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003eA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\"\u003e\n \u003cp\u003e86 (85.15)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\"\u003e\n \u003cp\u003e56 (76.71)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\"\u003e\n \u003cp\u003e6 (5.94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\"\u003e\n \u003cp\u003e7 (9.59)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003eN-A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\"\u003e\n \u003cp\u003e15 (14.85)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\"\u003e\n \u003cp\u003e17 (23.29)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\"\u003e\n \u003cp\u003e95 (94.06)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\"\u003e\n \u003cp\u003e66 (9.04)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003eFEC\u003csup\u003e\u0026nbsp;\u003c/sup\u003e,n\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003e3.0 (2.0\u0026minus;5.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\" valign=\"top\"\u003e\n \u003cp\u003e3.0 (2.0\u0026minus;4.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e0.244\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\"\u003e\n \u003cp\u003e2.0 (1.0\u0026minus;3.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\"\u003e\n \u003cp\u003e2.0 (1.0\u0026minus;3.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e0.994\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003eDEC (n,%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e0.723\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e0.756\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\"\u003e\n \u003cp\u003etwo-way\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\"\u003e\n \u003cp\u003e82 (81.19)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\"\u003e\n \u003cp\u003e59 (80.82)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\"\u003e\n \u003cp\u003e78 (97.50)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\"\u003e\n \u003cp\u003e57 (96.61)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\"\u003e\n \u003cp\u003eforward\u003csup\u003e\u0026nbsp;\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\"\u003e\n \u003cp\u003e8 (7.92)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\"\u003e\n \u003cp\u003e7 (9.59)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\"\u003e\n \u003cp\u003e2 (2.50)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\"\u003e\n \u003cp\u003e2 (3.39)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\"\u003e\n \u003cp\u003ereverse\u003csup\u003e\u0026nbsp;\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\"\u003e\n \u003cp\u003e5 (4.95)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\"\u003e\n \u003cp\u003e2 (2.74)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\" valign=\"top\"\u003e\n \u003cp\u003e0 (0.00)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\" valign=\"top\"\u003e\n \u003cp\u003e0 (0.00)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003eEMBLP (n,%)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e0.873\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e0.738\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003eType I\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\"\u003e\n \u003cp\u003e7 (6.93)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\"\u003e\n \u003cp\u003e4 (5.48)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\"\u003e\n \u003cp\u003e11 (10.89)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\"\u003e\n \u003cp\u003e10(13.70)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003eType II\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\"\u003e\n \u003cp\u003e45 (44.55)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\"\u003e\n \u003cp\u003e32 (43.84)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\"\u003e\n \u003cp\u003e46 (45.54)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\"\u003e\n \u003cp\u003e35 (47.95)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003eType III\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003e49 (48.51)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\" valign=\"top\"\u003e\n \u003cp\u003e37 (50.68)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\" valign=\"top\"\u003e\n \u003cp\u003e44 (43.56)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\" valign=\"top\"\u003e\n \u003cp\u003e28 (38.36)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003eEMBLB (n,%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e0.025\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e0.009\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp;\u0026lt;5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003e38 (37.62)（37.62%）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\" valign=\"top\"\u003e\n \u003cp\u003e40 (54.79)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\"\u003e\n \u003cp\u003e34 (33.66)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\"\u003e\n \u003cp\u003e39 (43.43)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp;\u0026ge;5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.174183514774494%\" valign=\"top\"\u003e\n \u003cp\u003e63 (62.38)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.552099533437014%\" valign=\"top\"\u003e\n \u003cp\u003e33 (45.21)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.020217729393469%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.640746500777606%\"\u003e\n \u003cp\u003e67 (66.34)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.573872472783826%\"\u003e\n \u003cp\u003e34 (46.58)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.864696734059098%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.1993769470405%\" valign=\"top\"\u003e\n \u003cp\u003eEV (cm\u003csup\u003e3\u003c/sup\u003e)\u003csup\u003e\u0026nbsp;\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.1993769470405%\" valign=\"top\"\u003e\n \u003cp\u003e2.76(2.07\u0026minus;3.97)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.601246105919003%\" valign=\"top\"\u003e\n \u003cp\u003e2.96 (2.31\u0026minus;3.74)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.853582554517134%\" valign=\"top\" colspan=\"2\"\u003e\n \u003cp\u003e0.682\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.666666666666668%\" valign=\"top\"\u003e\n \u003cp\u003e3.20 (2.37\u0026minus;4.40)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.601246105919003%\" valign=\"top\"\u003e\n \u003cp\u003e3.20 (2.43\u0026minus;4.04)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.878504672897197%\" valign=\"top\"\u003e\n \u003cp\u003e0.663\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eForward: Cervico-to-fundal movement.\u003c/p\u003e\n\u003cp\u003eReverse:\u0026nbsp;fundal-to-cervical movement.\u003c/p\u003e\n\u003cp\u003eAbbreviations: EMT endometrial thickness; EMP endometrial pattern; FEC frequency of endometrial contraction; DEC direction of endometrial contraction; EMBLP endometrial blood flow pattern; EMBLB endometrial blood flow branches; EV endometrial volume.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eChanges in endometrial blood flow parameters\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIt was found that different pregnancy outcome samples did not show significant differences in the changes in endometrial blood flow and blood flow branch between the day of progesterone initiation and the day before FET (Table 3).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3.\u003c/strong\u003e Comparison of changes in endometrial blood flow indices from the day of progesterone administration to the day before embryo transfer between pregnant and non-pregnant patients\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"99%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"47.333333333333336%\"\u003e\n \u003cp\u003e\u003cstrong\u003eparameters\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.333333333333332%\"\u003e\n \u003cp\u003e\u003cstrong\u003ePregnant group\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.5%\"\u003e\n \u003cp\u003e\u003cstrong\u003eNon-pregnant group\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.833333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003eP\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003e-value\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"47.333333333333336%\"\u003e\n \u003cp\u003eNumber of patients\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.333333333333332%\"\u003e\n \u003cp\u003e101\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.5%\"\u003e\n \u003cp\u003e73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.833333333333334%\"\u003e\n \u003cp\u003e\u003cem\u003e---\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"47.333333333333336%\"\u003e\n \u003cp\u003eChange in EMBLP (n, %)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.333333333333332%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.5%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.833333333333334%\"\u003e\n \u003cp\u003e0.671\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"47.333333333333336%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; N-Change\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.333333333333332%\"\u003e\n \u003cp\u003e83 (82.18)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.5%\"\u003e\n \u003cp\u003e60（82.19）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.833333333333334%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"47.333333333333336%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; I-II\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.333333333333332%\"\u003e\n \u003cp\u003e2 (1.98)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.5%\"\u003e\n \u003cp\u003e3(4.11)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.833333333333334%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"47.333333333333336%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; II-III\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.333333333333332%\"\u003e\n \u003cp\u003e16 (15.84)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.5%\"\u003e\n \u003cp\u003e10（13.70）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.833333333333334%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"47.333333333333336%\"\u003e\n \u003cp\u003eChange in EMBLB(n, %)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.333333333333332%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.5%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.833333333333334%\"\u003e\n \u003cp\u003e0.398\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"47.333333333333336%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; N-Change\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.333333333333332%\"\u003e\n \u003cp\u003e84 (83.17)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.5%\"\u003e\n \u003cp\u003e57 (78.08)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.833333333333334%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"47.333333333333336%\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Increasement\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.333333333333332%\"\u003e\n \u003cp\u003e17 (16.83)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.5%\"\u003e\n \u003cp\u003e16 (21.92)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.833333333333334%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eN-Change: no significant change in parameters at two time points\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIncrement: blood flow branches from \u0026lt;5 on the day of transformation to\u0026nbsp;\u0026ge;5 on the day before transfer\u003c/p\u003e\n\u003cp\u003eAbbreviations: EMBLP, endometrial blood flow pattern; EMBLB, endometrial blood flow branches\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eLogistic regression and\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003e\u0026nbsp;receiver operating characteristics curve analysis\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBinary stepwise logistic regression analysis was performed to identify the covariates independently associated with the primary outcome of clinical pregnancy (Table 4). After adjusting for age, AFC, number of embryos transferred, embryo level, the proportion of good-quality embryo transfer, endometrial type, and endometrial blood flow branches, and changes of blood flow at two time points, only the endometrial blood flow branches on the day before embryo transfer significantly improved the chance of pregnancy, with ORs of 2.745 (95% CI: 1.054\u0026minus;7.153, P=0.039).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 4.\u0026nbsp;\u003c/strong\u003eLogistic regression analysis to identify covariates independently associated with the clinical pregnancy\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"112%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"30.383480825958703%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003eCovariates\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.663716814159294%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003eLogistic regression coefficient (B)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.811209439528024%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003eAdjusted OR (95% CI)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.522123893805309%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003eP\u003cem\u003e-\u003c/em\u003evalue\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003eAge\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e-0.066\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e0.936\u0026nbsp;(0.857\u0026minus;1.023)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003e0.144\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003eAFC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e0.032\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e1.033\u0026nbsp;(0.978\u0026minus;1.090)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003e0.246\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003eNo. of embryos transferred\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e0.733\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e2.080\u0026nbsp;(0.962\u0026minus;4.498)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003e0.063\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003eBlastocysts transfer\u0026nbsp;e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003eNO\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003eRef.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003eYES\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e0.674\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e1.963 (0.884\u0026minus;4.358)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003e0.098\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003eGood quality embryo transfer\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003eNO\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003eRef.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003eYES\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e0.029\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e1.030 (0.462\u0026minus;2.295)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003e0.943\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003eEMBLB on the endometrial transformation day\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003e\u0026lt;5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003eRef.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003e\u0026ge;5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e0.114\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e1.121 (0.464\u0026minus;2.707)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003e0.800\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003eEMBLB on the day before embryo transfer\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003e\u0026lt;5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003eRef.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003e\u0026ge;5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e1.010\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e2.745 (1.054\u0026minus;7.153)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003e0.039\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003eChange in EMBLB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003eN-Change\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003eRef.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.80354505169867%\" style=\"width: 33.425%;\"\u003e\n \u003cp\u003eIncrement\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"27.178729689807977%\" style=\"width: 29.8487%;\"\u003e\n \u003cp\u003e0.851\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25.849335302806498%\" style=\"width: 28.4732%;\"\u003e\n \u003cp\u003e2.343 (0.721\u0026minus;7.608)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.533234859675037%\" style=\"width: 8.2531%;\"\u003e\n \u003cp\u003e0.157\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eAbbreviations: AFC antral follicle; EMBLB endometrial blood flow branches; OR odds ratio; CI confidence interval.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe results of this study demonstrated that measuring the endometrial blood perfusion using PD-US was shown to be a simple and effective method for predicting pregnancy outcomes during the HRT-FET cycle. Embryos are estimated to account for one-third of implantation failures, whereas poor endometrial receptivity and altered embryo endometrial dialogue account for the remaining two-thirds [10]. Several studies have examined EMT, endometrial type, subendometrial contraction, and endometrial volume\u0026nbsp;and have attempted to provide a clear overview of the implantation window. However, contradictory findings have been reported [11,12]. The above-mentioned ultrasound endometrial indicators were not the final factors affecting pregnancy outcomes in our study.\u003c/p\u003e\n\u003cp\u003eThis study evaluated the role of PD-US in predicting pregnancy during HRT-FET cycles by counting endometrial and subendometrial blood flow branches. The pregnant group was younger and had higher AFC values. However, after adjusting for these parameters, the branches of the\u0026nbsp;spiral arteries on the day before transplantation were the only factors that affected pregnancy outcomes. While Wang et al. concluded that the coexistence of endometrial and subendometrial blood flow results in a higher embryo implantation rate [13], our results suggest that blood perfusion is more important than the endometrial\u0026minus;subendometrial blood flow distribution pattern. Blood supply to the endometrium comes from the radial artery, which passes through the connection between the uterine muscle and endometrium, divides into basal arteries that supply the basal layer, and then forms a spiral artery to reach the surface of the endometrium. At the junction of the myometrium and endometrium, ultrasonography shows a low-echo area called the subendometrial area. Histological studies have confirmed that this area is the innermost layer of the myometrium, or the junction zone [14]. Compared to the outer muscular layer, our results showed that blood flow in the junction zone was more abundant in most cases. Thus, whether the branch enters the endometrium the day before embryo transfer may not be an absolute factor affecting pregnancy outcomes; rather, the richness of blood flow in the endometrium or junction zone is suggested as a predictive factor.\u003c/p\u003e\n\u003cp\u003eIn this study, all five patients with endometrial blood flow branches \u0026gt;10 on the progesterone start day were pregnant, while five with blood flow branches \u0026gt;10 on the day before transplantation had conceived. Therefore, we emphasize the possible positive relationship between the abundance of blood flow during the secretory phase and pregnancy; however, it should not be concluded that patients without endometrial or subendometrial blood flow branches have absolutely low implantation and pregnancy rates. In patients with blood flow branch counts of 0\u0026minus;1 on either the day of transformation or the day before transplantation, we did not find a linear correlation between no blood flow and pregnancy. These data indicate that there may be a certain threshold for endometrial vascularization, that, when reached, has a significant positive impact on clinical pregnancy. Whether the research conclusions can become a reference option for selective embryo transfer or guide clinical medication requires further large-scale prospective cohort studies.\u003c/p\u003e\n\u003cp\u003eNg et al. [15] reported that the measurement of endometrial and subendometrial blood flow using 3D PD-US could not predict pregnancy well if measured at a time point during IVF treatment. Due to baseline differences between patients in the present study, we compared the changes in 3D PD-US parameters of the endometrium at the two time points. However, we failed to confirm that the changes on the day of endometrial transformation and the day before embryo transfer were significantly different between the pregnant and non-pregnant groups. It has not been confirmed whether this change has any role in predicting HRT-FET results, and the main variable determining pregnancy outcomes is endometrial blood flow during the peri-transplantation period.\u003c/p\u003e\n\u003cp\u003eThis study had the advantage of being the first prospective cohort study to use PD-US to detect endometrial receptive ultrasound indicators at two time points after HRT-FET. Due to the inconsistent Doppler signal waveforms of these small spiral vessels, predicting pregnancy using the spiral artery Doppler flow index is highly controversial [16-18]; thus, our study did not measure the subendometrial vascularization flow index but instead chose a more intuitive indicator for assessing blood perfusion. Previous studies have reported that blood flow to the endometrium affects pregnancy outcomes after freeze-thawed embryo transfer. However, the detection methods were not consistent. Jinno et al. [19] measured endometrial tissue blood flow (ETBF) using laser blood flowmetry and found that women with an endometrial microvascular blood flow of at least 29 mL/min per 100 g of tissue in the early luteal phase had a significantly higher pregnancy rate, with 85% of gestational sacs in normal uteri implanted in the uterine regions with the highest measured ETBF. Other studies have demonstrated that the levels of vascular endothelial growth factor and its receptors significantly increase during the peri-implantation period [20-22]. Additionally, 3D Doppler angiography has been shown to quantitatively evaluate vascular density and blood flow in the endometrium and subendometrium [23]. However, none of these methods have the operability of real-time monitoring during endometrial preparation for FET, whereas 3D PD-US can achieve the convenience of bedside monitoring.\u003c/p\u003e\n\u003cp\u003eThere was a limitation to the current study. Most patients refused to undergo transvaginal ultrasound on the day of embryo transfer. Therefore, after endometrial transformation, we performed a second endometrial receptivity test in the afternoon before transplantation, and there may have been some deviations from the actual values on the day of transplantation.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eMeasuring the endometrial and subendometrial blood flow branches on the day of the peri-transplantation period during the HRT-FET cycle using PD-US was shown to be a simple and effective method for predicting pregnancy outcomes. In the future, the development of ultrasound may improve the consistency of endometrial blood flow assessment and generate more accurate non-invasive blood flow assessment methods for daily clinical practice, such as microvascular flow ultrasound.\u0026nbsp;\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eHRT-FET\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;hormone replacement therapy-frozen embryo transfer\u003c/p\u003e\n\u003cp\u003eIVF\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;in vitro fertilization \u0026nbsp; \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ePD-US\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;power Doppler ultrasound\u003c/p\u003e\n\u003cp\u003eEMT\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;endometrial thickness\u003c/p\u003e\n\u003cp\u003eAFC\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;antral follicles\u003c/p\u003e\n\u003cp\u003eOR\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;odd ratio\u003c/p\u003e\n\u003cp\u003eCI \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;confidence interval\u003c/p\u003e\n\u003cp\u003e3D\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;three-dimensional\u003c/p\u003e\n\u003cp\u003eETBF\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;endometrial tissue blood flow\u003c/p\u003e\n\u003cp\u003eEMP \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;endometrial pattern\u003c/p\u003e\n\u003cp\u003eFEC \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;frequency of endometrial contraction\u003c/p\u003e\n\u003cp\u003eDEC \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;direction of endometrial contraction\u003c/p\u003e\n\u003cp\u003eEMBLP \u0026nbsp;\u0026nbsp;\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;endometrial blood flow pattern\u003c/p\u003e\n\u003cp\u003eEMBLB \u0026nbsp;\u0026nbsp;\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;endometrial blood flow branches\u003c/p\u003e\n\u003cp\u003eEV \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; endometrial volume\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Scientific Ethics Committee of Chengdu Women\u0026rsquo;s and Children\u0026rsquo;s Central Hospital (reference: B2021-7), and all enrolled patients provided informed consent.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interest\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors report no conflict of interest for this work.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that no funds, grants, or other support were received during the preparation of this manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eXue Ke conducted the data analyses and manuscript drafting. XF Liang\u0026nbsp;contributed to the data collection. YH Lin and Fang Wang were responsible for the interpretation of the data and revision of the article. All authors critically reviewed and approved the final version of the article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to thank the staff of the Department of Assisted Reproduction at Chengdu Women\u0026rsquo;s and Children\u0026rsquo;s Central Hospital for their cooperation and support.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eCraciunas L, Gallos I, Chu J, Bourne T, Quenby S, Brosens JJ, et al. Conventional and modern markers of endometrial receptivity: a systematic review and meta-analysis. Hum Reprod Update. 2019;25:202-23.\u003c/li\u003e\n\u003cli\u003eLiu WJ, Nong YQ, Ruan JX, Chen Y, Fan L, Huang QW, et al. Impact of endometrial thickness during menstruation and endometrial scratching on the pregnancy in frozen-thawed embryo transfer. J Obstet Gynaecol Res. 2019;45:619-25. \u003c/li\u003e\n\u003cli\u003eOluborode B, Burks H, Craig LB, Peck JD. Does the ultrasound appearance of the endometrium during treatment with assisted reproductive technologies influence pregnancy outcomes? Hum Fertil (Camb). 2022;25:166-75.\u003c/li\u003e\n\u003cli\u003eMartins RS, Oliani AH, Oliani DV, de Oliveira JM. Continuous endometrial volumetric analysis for endometrial receptivity assessment on assisted reproductive technology cycles. BMC Pregnancy Childbirth. 2020;20:663.\u003c/li\u003e\n\u003cli\u003eZhang CH, Chen C, Wang JR, Wang Y, Wen SX, Cao YP, et al. An endometrial receptivity scoring system basing on the endometrial thickness, volume, echo, peristalsis, and blood flow evaluated by ultrasonography. Front Endocrinol (Lausanne). 2022;13:907874.\u003c/li\u003e\n\u003cli\u003eNg EH, Chan CC, Tang OS, Yeung WS, Ho PC. The role of endometrial and subendometrial blood flows measured by three-dimensional power Doppler ultrasound in the prediction of pregnancy during IVF treatment. Hum Reprod. 2006;21:164-70.\u003c/li\u003e\n\u003cli\u003eChoi YJ, Lee HK, Kim SK. Doppler ultrasound investigation of female infertility. Obstet Gynecol Sci. 2023;66:58\u0026ndash;68.\u003c/li\u003e\n\u003cli\u003eApplebaum M. The uterine biophysical profile. Ultrasound Obstet Gynecol. 1995;5:67-8.\u003c/li\u003e\n\u003cli\u003eNg EH, Chan CC, Tang OS, Yeung WS, Ho PC. Factors affecting endometrial and subendometrial blood flow measured by three-dimensional power Doppler ultrasound during IVF treatment. Hum Reprod. 2006;21:1062-9.\u003c/li\u003e\n\u003cli\u003eFranasiak JM, Forman EJ, Hong KH, Werner MD, Upham KM, Treff NR, et al. The nature of aneuploidy with increasing age of the female partner: a review of 15169 consecutive trophectoderm biopsies evaluated with comprehensive chromosomal screening. Fertil Steril. 2014;101:656-63.\u003c/li\u003e\n\u003cli\u003eHaas J, Casper RF. Observations on clinical assessment of endometrial receptivity. Fertil Steril. 2022;118:828-31.\u003c/li\u003e\n\u003cli\u003eSon JB, Jeong JE, Joo JK, Na YJ, Kim CW, Lee KS. Measurement of endometrial and uterine vascularity by transvaginal ultrasonography in predicting pregnancy outcome during frozen-thawed embryo transfer cycles. J Obstet Gynaecol Res. 2014;40:1661-7.\u003c/li\u003e\n\u003cli\u003eWang L, Qiao J, Li R, Zhen X, Liu Z. Role of endometrial blood flow assessment with color Doppler energy in predicting pregnancy outcome of IVF-ET cycles. Reprod Biol Endocrinol. 2010;18:122.\u003c/li\u003e\n\u003cli\u003eChien LW, Au HK, Chen PL, Xiao J, Tzeng CR. 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Ann Transl Med. 2020;8:944. \u003c/li\u003e\n\u003cli\u003eWu HM, Chiang CH, Huang HY, Chao AS, Wang HS, Soong YK. Detection of the subendometrial vascularization flow index by three-dimensional ultrasound may be useful for predicting the pregnancy rate for patients undergoing in vitro fertilization-embryo transfer. Fertil Steril. 2003;79:507-11. \u003c/li\u003e\n\u003cli\u003eJinno M, Ozaki T, Iwashita M, Nakamura Y, Kudo A, Hirano H. Measurement of endometrial tissue blood flow: a novel way to assess uterine receptivity for implantation. Fertil Steril. 2001;76:1168-74.\u003c/li\u003e\n\u003cli\u003eLicht P, Russu V, Lehmeyer S, Wissentheit T, Siebzehnr\u0026uuml;bl E, Wildt L. Cycle dependency of intrauterine vascular endothelial growth factor levels is correlated with decidualization and corpus luteum function. Fertil Steril. 2003;80:1228-33.\u003c/li\u003e\n\u003cli\u003eMalamitsi-Puchner A, Sarandakou A, Tziotis J, Stavreus-Evers A, Tzonou A, Landgren BM. Circulating angiogenic factors during periovulation and the luteal phase of normal menstrual cycles. Fertil Steril. 2004;81:1322-7.\u003c/li\u003e\n\u003cli\u003eNayak NR, Brenner RM. Vascular proliferation and vascular endothelial growth factor expression in the rhesus macaque endometrium. J Clin Endocrinol Metab. 2002;87:1845-55.\u003c/li\u003e\n\u003cli\u003eChen L, Quan S, Li H, Chen C, Xing F, Yu Y. A comparison of endometrial and subendometrial vascularity assessed by three-dimensional ultrasonography and power Doppler angiography between healthy fertile women and women with unexplained primary recurrent miscarriage. Fertil Steril. 2011;95:1127-9.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"reproductive-biology-and-endocrinology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"rbej","sideBox":"Learn more about [Reproductive Biology and Endocrinology](http://rbej.biomedcentral.com)","snPcode":"12958","submissionUrl":"https://submission.nature.com/new-submission/12958/3","title":"Reproductive Biology and Endocrinology","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Power Doppler ultrasound, endometrial receptivity, endometrial blood flow, frozen embryo transfer","lastPublishedDoi":"10.21203/rs.3.rs-3257917/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3257917/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eThis study aimed to assess the predictive value of endometrial blood flow branches on pregnancy outcomes after hormone replacement therapy-frozen embryo transfer (HRT-FET).\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003e This prospective observational study involved 174 reproductive-aged women who underwent endometrial receptivity assessment in a tertiary care academic medical center in southwest China using power Doppler ultrasonography during HRT-FET. On the day of endometrial transformation and the day before embryo transfer, three-dimensional power Doppler ultrasound was performed. The endometrial blood flow branches of endometrial and subendometrial regions were compared in non-pregnant and pregnant groups at the two time points above.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe endometrial blood flow branches were higher in pregnant patients than in non-pregnant patients on the day of endometrial transformation (P\u0026thinsp;=\u0026thinsp;0.025) and the day before embryo transfer (P\u0026thinsp;=\u0026thinsp;0.009). Changes in endometrial blood flow pattern and endometrial blood flow branches at the two time points did not differ among the pregnancy outcome samples. After adjusting for age, antral follicles, and embryos transferred, the endometrial blood flow branches on the day before embryo transfer was the independent factor influencing the chance of clinical pregnancy, with an odds ratio of 2.745 (95% confidence interval: 1.054\u0026ndash;7.153, P\u0026thinsp;=\u0026thinsp;0.039).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eEndometrial blood flow perfusion during the peri-transplantation period of the HRT-FET cycle is a good indicator of pregnancy outcomes, suggesting that valuation of endometrial branches via power Doppler ultrasound is a simple and effective approach for achieving indicator measurements.\u003c/p\u003e","manuscriptTitle":"Pregnancy prediction via ultrasound-detected endometrial blood for hormone replacement therapy-frozen embryo transfer: a prospective observational study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-08-18 15:40:54","doi":"10.21203/rs.3.rs-3257917/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revision","date":"2023-09-27T06:04:13+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2023-09-27T03:21:34+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"de1a52ea-ae8d-4c95-af4a-27f757bf3132","date":"2023-09-15T06:41:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"0a2fee45-7af4-4b70-9392-a91ff4d4d061","date":"2023-09-02T06:36:13+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"8a870051-e7a9-45f4-9b49-8115d2569f48","date":"2023-08-30T10:31:12+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2023-08-23T04:06:26+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"78357b31-f6aa-43cf-83cf-d82e89cbec68","date":"2023-08-19T09:43:00+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"da8f09c6-3665-4cb0-a2af-756910460d6a","date":"2023-08-19T04:07:11+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2023-08-18T10:04:30+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2023-08-14T13:49:55+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2023-08-14T13:49:55+00:00","index":"","fulltext":""},{"type":"submitted","content":"Reproductive Biology and Endocrinology","date":"2023-08-12T10:19:10+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"reproductive-biology-and-endocrinology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"rbej","sideBox":"Learn more about [Reproductive Biology and Endocrinology](http://rbej.biomedcentral.com)","snPcode":"12958","submissionUrl":"https://submission.nature.com/new-submission/12958/3","title":"Reproductive Biology and Endocrinology","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"cab238ec-cf3b-44b1-a927-7bd149aff0c9","owner":[],"postedDate":"August 18th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2023-11-27T15:06:53+00:00","versionOfRecord":{"articleIdentity":"rs-3257917","link":"https://doi.org/10.1186/s12958-023-01164-9","journal":{"identity":"reproductive-biology-and-endocrinology","isVorOnly":false,"title":"Reproductive Biology and Endocrinology"},"publishedOn":"2023-11-24 15:01:12","publishedOnDateReadable":"November 24th, 2023"},"versionCreatedAt":"2023-08-18 15:40:54","video":"","vorDoi":"10.1186/s12958-023-01164-9","vorDoiUrl":"https://doi.org/10.1186/s12958-023-01164-9","workflowStages":[]},"version":"v1","identity":"rs-3257917","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3257917","identity":"rs-3257917","version":["v1"]},"buildId":"_2-kVJe1T_tPrBINL-cwx","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}