Endometrial echo patterns of embryo transfer day affect pregnancy outcomes in frozen embryo transfer cycles: a retrospective clinical study

Endometrial echo patterns of embryo transfer day affect pregnancy outcomes in frozen embryo transfer cycles: a retrospective clinical 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 Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Endometrial echo patterns of embryo transfer day affect pregnancy outcomes in frozen embryo transfer cycles: a retrospective clinical study Xi Cheng, Bin Yang, Li Wang, Jinzhao Ma, Xuan Huang, Kadiliya Jueraitetibaike, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3955580/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 10 Apr, 2025 Read the published version in BMC Pregnancy and Childbirth → Version 1 posted 10 You are reading this latest preprint version Abstract Background: Echo pattern is the ultrasonic index reflecting endometrial proliferation and/or stromal decidualization. However, consensus of endometrial echo pattern and IVF pregnant outcomes is lacking in clinical application. Methods : The retrospective cohort study analyzed the data from the electronic records of women who underwent frozen embryo transfer (FET) with hormone replacement treatment (not only one cycle per patient) between July 2020 to August 2021 at Reproduction Medicine Center of Jinling Hospital of Medical College of Nanjing University. A total of 159 cleavage stage embryo transfer cycles and 540 blastocyst transfer cycles were analyzed in this study. Transvaginal ultrasound scans were performed on the embryo transfer day. The endometrial echo pattern was classified into four types: A, B, B-C and C. Pattern A was defined as trilinear type, Pattern B, B-C and C were defined as not trilinear type. All scans were conducted by experienced clinicians, and the images were reviewed by the same two physicians. The outcomes measured included embryo implantation rate, clinical pregnancy rate, first trimester abortion rate, and live birth rate. Results: The embryo implantation rate ( p =0.066), clinical pregnancy rate ( p =0.140), early abortion rate ( p =0.515) and live birth rate ( p =0.578) were similar between the 4 type of endometrial pattern groups in cleavage-stage embryo FET cycles. In blastocyst cycles, the implantation rate ( p =0.201) and clinical pregnancy rate ( p =0.555) did not differ between the four endometrial patterns. Patients with a Pattern A endometrium on blastocyst transfer day experienced a decreased live birth rate (19.05%) compared with Pattern B, Pattern B-C and Pattern C ( p =0.006. p =0.008, p =0.031 for Pattern A vs . Pattern B, Pattern A vs . Pattern B-C, Pattern A vs . Pattern C). The first trimester abortion rate of Pattern A is up to 40.00%, although there was no statistical difference ( p =0.118). In the cycles of not trilinear type group, the early miscarriage rate (0.248 [95% CI, 0.067–0.914]; p=0.036) was lower and the live birth rate (0.269 [95% CI, 0.089–0.810]; p=0.020) was higher than trilinear type group. Conclusions: Our retrospective study suggests that a trilinear pattern endometrium on blastocyst transfer was associated with a higher first trimester abortion rate and lower live birth rate. FET Endometrial echo patterns First trimester abortion rate Live birth rate Figures Figure 1 Figure 2 Figure 3 Introduction The success of IVF-ET ( In vitro fertilization and embryo transfer) relies on a high-quality embryo, a receptive endometrium, and a healthy maternal condition. The endometrium, undergoing a series of structural and biochemical changes during the reproductive cycle, must be in a receptive phase [ 1 , 2 ]. For decades, reproductive scientists have worked diligently to identify a suitable method for assessing endometrial receptivity. Currently, transvaginal ultrasonography is the most widely used in clinical practice, which provided clinicians with a non-invasive approach for monitoring endometrial development throughout the menstrual cycle. Endometrial thickness and echo pattern are the most commonly used markers for evaluating endometrial receptivity in transvaginal ultrasonography examine. Numerous studies suggest that endometrial thickness is an independent predictor of pregnancy occurrence [ 3 , 4 ]. Regarding the endometrial echo pattern, however, consensus is lacking in clinical application. Endometrial echo patterns observed sonographically are categorized as triple line (TL), appearing multilayered with hyperechogenic outer walls and a distinct central echogenic line; isoechogenic (IE), where the endometrium exhibits the same echogenicity as the myometrium with a poorly defined central echogenic line; and homogeneous hyperechogenic (HH), presenting as an entirely echodense endometrium, more echogenic than the myometrium without a visible central echogenic line [ 5 ]. The endometrium transitions from a triple line pattern to a non-triple line pattern in the natural cycle under the action of steroid hormones. Currently, there exists controversy over whether echo patterns are associated with clinical outcomes. Previous research predominantly focused on the late proliferative phase in ovarian stimulation cycles. Some studies reported that endometrial pattern on the day of hCG injection or progesterone administration was not associated with pregnancy outcomes in ART [ 6 – 12 ], while some studies reported higher pregnancy rates among women with trilinear endometrial pattern, compared to those with semitrilinear or unilinear endometrial patterns [ 9 , 13 , 14 ]. Regarding the secretory phase, J H Check et al. observed decreased pregnancy and implantation rates in cycles where the homogeneous hyperechogenic pattern did not occur three days after transfer[ 15 , 16 ]. A nonhomogeneous endometrial echo pattern in the midluteal phase was identified as a potential factor in unexplained infertility [ 17 ]. However, some studies reported that the endometrial pattern on the day of D2/D3 embryo transfer was not associated with pregnancy outcomes in IVF-ET cycles [ 8 , 18 ]. In assisted reproduction treatment, clinicians pay close attention to endometrial thickness and pattern in the proliferative phase. Embryo implantation is rarely canceled due to endometrial factors after endometrial transformation. However, whether the endometrial pattern on embryo transfer day affects pregnancy outcomes remains unclear. In this manuscript, we conducted a retrospective analysis of 699 FET cycles at our reproductive medicine center. We selected FET cycles using an exogenous estrogen and progesterone protocol to minimize variables potentially affecting the endometrium in each cycle. The study's objective was to thoroughly assess the relationship between the sonographic endometrial pattern on embryo transfer day and pregnancy outcomes in women undergoing hormonally prepared FET cycles. Methods and materials Patients and study design We conducted a retrospective cohort study, collecting data from the electronic records of women who underwent FET cycles (more than one cycle per patient) via hormone replacement treatment with or without GnRHa from July 2020 to August 2021 at the Reproduction Medicine Center of Jinling Hospital, Medical College of Nanjing University (Nanjing, China). The exclusion criteria were: (a) age over 44 years; (b) coexisting hydrosalpinx, endometrial lesions, or an abnormal uterine environment (uterine fibroids protruding into the uterine cavity, submucosal fibroids, uterine adhesions, etc.); (c) uterine anomalies; (d) moderate or severe endometriosis or adenomyosis. Patients underwent no therapeutic interventions apart from routine procedures. Monitoring and management followed the standardized clinical protocols of the hospital. The embryos at the cleavage stage were evaluated according to the Istanbul consensus [ 19 ]. Cleavage-stage (D3) high-quality embryos were defined as having 6–10 cells, with fragments < 30% and no severe asymmetry. Blastocysts were assessed on D5-D7 based on the criteria of Gardner [ 20 ]. Blastocysts with a score higher than 3BB were categorized as high-quality blastocysts. Transvaginal ultrasound scans (TVUS) were performed on the day of cleavage-stage embryo or blastocyst transfer. All scans were conducted by experienced clinicians, and the images were printed and reviewed by the same two physicians. The endometrial echo pattern was classified into three types [ 21 , 22 ]: Pattern A, Pattern B, and Pattern C. Pattern A represented a multilayered "triple-line" endometrium, consisting of a central hyperechogenic line surrounded by two hypoechoic layers; Pattern B was characterized as an isoechogenic pattern relative to the surrounding myometrium with an unclear central hyperechogenic line; Pattern C displayed a homogeneous, hyperechogenic endometrium with increased reflectivity compared to the myometrium. An intermediate pattern B-C featured a gradual increase in reflectivity from the peripheral region to the central line. Endometrium of Pattern A was defined as trilinear type, and endometrium of Pattern B, B-C and C were defined as not trilinear type. Images of the four endometrial patterns are presented in Supplementary Fig. 1. The outcomes measured included embryo implantation rate, clinical pregnancy rate, first trimester abortion rate, and live birth rate. Pregnancy outcomes were followed up by phone and recorded in our electronic medical record. All data were collected using an exclusive internal database at our reproductive medicine center, ensuring patient data security through advanced threat prevention and periodic password renewals for user access. The methodological pipeline is illustrated in Fig. 1 . The endometria specimen demonstrated in this manuscript were collected on the 5th day after ovulation. The study procedures were approved by the Clinical Ethics Review Committee of Nanjing Jinling Hospital. Endometrial preparation and embryo transfer In the early stages of menstruation (between the second and fourth day of the menstrual cycle), patients underwent a sex hormone serum test and transvaginal ultrasonography examination. If GnRHa-HRT protocol was applied, 3.75 mg of triptorelin acetate (Ipsen Pharma Biotech) was administered on the the second and fourth day of the menstrual cycle, a sex hormone serum test and transvaginal ultrasonography examination were applied 28–35 days later. Those without abnormalities commenced oral intake of a fixed dose of exogenous estradiol for 10–16 days (Femoston, 4 mg b.i.d.). Serum E2 and P levels, along with endometrial thickness, were monitored to exclude premature ovulation. Patients with low endometrial thickness received additional vaginal medication (Femoston, 2 mg estradiol q.d.). Upon achieving the requisite endometrial thickness (≥ 8 mm), oral estradiol was combined with dydrogesterone compound tablets (Femoston, 4 mg estradiol and 20 mg dydrogesterone b.i.d. × 4 or 6 days), supplemented with a vaginal progesterone soft capsule (Utrogestan, 400mg b.i.d.) to induce endometrial transformation. Cleavage-stage embryos were thawed and transferred on the fifth day of endometrial transformation, and blastocysts on the seventh day. TVUS assessed the endometrial thickness and echo pattern, and serum E2 and P levels were measured on the embryo transfer day. For luteal support, patients typically continued Femoston (4 mg estradiol and 20 mg dydrogesterone, b.i.d.) and vaginal progesterone soft capsule (Utrogestan, 400mg b.i.d.). Serum β-human chorionic gonadotropin (β-hCG) was detected 2 weeks post-embryo transfer to determine biochemical pregnancies. Transvaginal ultrasound was performed 4 weeks post-embryo transfer in patients with positive β-hCG results to confirm clinical pregnancies and the number of implanted embryos. A clinical pregnancy was identified by the presence of a gestational sac. Luteal support in pregnant patients was sustained until 2 months post-embryo transfer. Follow-up was conducted to detect abnormalities during pregnancy. Early miscarriage was defined as spontaneous abortion occurring before 12 weeks of pregnancy. Live birth was defined as the delivery of a living newborn after the 28th gestational week, with live birth rate calculated as the ratio of live birth cycle number to the number of embryo transfer cycles. Immunohistochemistry staining The endometrial samples were fixed in neutral buffered formalin (NBF). Following deparaffinization and rehydration, the sections were subjected to antigen retrieval. Afterward, the sections were incubated with primary antibody of antibodies against Estrogen receptor α (DAKO), Estrogen receptor β (Abcam) or Progesterone receptor (DAKO) overnight at 4°C. Subsequently, the slides were incubated with secondary antibody at room temperature. Haematoxylin was used to counterstain the sections. Statistical analysis SPSS 26.0 (SPSS Inc., Chicago, IL, USA) software was used for statistical analysis. Chi-square testing was introduced for analysis, supported by Fisher's exact test with Monte Carlo simulation for expected cell frequencies below five. Measurement data are assessed for normality using histograms. Data fitting the normal distribution are depicted as mean ± standard deviation and analyzed with one-way ANOVA to compare group differences. For non-normal distributions, data are shown as medians (interquartile ranges) and analyzed by the Kruskal-Wallis H test. Univariate analysis was used to preliminarily evaluate variables related to the clinical pregnancy outcome, and a multivariable logistic regression model was further employed to analyze the effect of endometrial echo patterns of embryo transfer day in HRT cycles on the clinical pregnancy outcome. Odds ratio (OR) and 95% confidence intervals (95% CI) were estimated using logistic regression. P < 0.05 was considered statistically significant. Results Characteristics of all FET cycles This study involved 699 HRT-FET cycles, including 159 cleavage stage embryo transfer cycles and 540 blastocyst transfer cycles. Transvaginal ultrasound scans were conducted on embryo transfer day, 1 to 3 hours before transfer operation. As shown in Fig. 2 , in cleavage-stage embryo cycles, 9 (6.50%) cycles were pattern A, 41 (29.7%) cycles were pattern B, 30 (21.7%) cycles were pattern B-C and 58 (42.0%) cycles were pattern C. In blastocyst cycles, 21 (3.74%) cycles were pattern A, 120 (21.39%) cycles were pattern B, 134 (23.89%) cycles were pattern B-C and 286 (50.98%) cycles w` ere pattern C. The demographic characteristics, the numbers and scores of embryos transferred are showed in Table 1 and Table 2 . No significant differences were noted between the groups regarding the female age, the body mass index (BMI), infertility type, infertility duration, the endometrial thickness on progesterone administration day, the number and grade of transferred embryos both in cleavage-stage embryo and blastocyst transfer cycles. Cycles with Pattern C endometrial patterns had a relatively thinner endometrial thickness on blastocyst transfer day compared with Pattern B group (10.37 ± 2.56 mm vs . 11.33 ± 2.84mm; p = 0.006). Cycles with Pattern C endometrial patterns had a higher serum estrogen level on endometrial transformation day compared with Pattern B-C group (1560.5 [1069.0-2838.0] pmol/L vs. 2067.0 [1168.0-5606.0] pmol/L; p = 0.037). Table 1 Characteristics of hormone replacement treatment FET cycles with 4 type of endometrial patterns on cleavage-stage embryo transfer day A (n = 9) B (n = 41) B-C (n = 30) C (n = 58) P value Age, years, mean (± SD) 35.44 ± 7.62 31.39 ± 5.34 34.4 ± 7.51 34.38 ± 6.19 0.076 BMI, kg/m2, mean (± SD) 22.49 ± 2.57 22.76 ± 3.63 24.33 ± 3.23 23.84 ± 3.41 0.169 Duration of infertility, years, median (25 th , 75 th percentile) 4.00 (1.50, 7.75) 3.00 (2.00, 4.00) 2.50 (1.50, 4.13) 3.00 (2.00, 5.13) 0.528 Infertility type Primary infertility, n (%) 4 (44.44%) 25 (60.98%) 17 (56.67%) 30 (51.72%) 0.733 Secondary infertility, n (%) 5 (55.56%) 16 (30.02%) 13 (43.33%) 28 (48.28%) Endometrial preparation protocol HRT 6 (66.67%) 31 (75.61%) 22 (73.33%) 33 (56.90%) 0.206 GnRHa-HRT 3 (33.33%) 10 (24.39%) 8 (26.67%) 25 (43.10%) The day of endometrial transformation Endometrial thickness, mm, mean (± SD) 9.37 ± 1.53 10.36 ± 1.62 10.26 ± 2.04 10.58 ± 2.43 0.432 Serum estrogen level, pmol/L, median (25 th , 75 th percentile) 1971.0 (1594.0, 2072.0) 1999.0 (1372.0, 5406.0) 1738.0 (1178.0, 2750.0) 2050.0 (1228.0, 6570.0) 0.740 Serum progesterone level, pmol/L, median (25 th , 75 th percentile) 1.37 (1.08, 1.69) 1.42 (0.66, 1.89) 1.44 (0.83, 2.16) 1.05 (0.80, 1.62) 0.417 The day of embryo transfer Endometrial thickness, mm, mean (± SD) 10.06 ± 2.13 10.93 ± 3.04 10.5 ± 2.23 10.97 ± 2.4 0.675 Serum estrogen level, pmol/L, median (25 th , 75 th percentile) 1680.0 (1441.0, 2284.0) 1659.0 (1062.0, 2276.0) 1695.5 (1196.0, 2268.0) 1714.5 (1109.0, 2540.0) 0.811 Serum progesterone level, pmol/L, median (25 th – 75 th percentile) 25.05 (23.06, 26.88) 26.46 (19.92, 33.42) 32.71 (26.31, 39.23) 29.81 (22.84, 36.11) 0.167 The increase percentage of endometrial thickness on embryo transfer day compared with endometrial transformation day (%) 5.88 (1.22, 19.77) 5.83 (-6.31, 15.79) 4.15 (-10.64, 15.91) 5.39 (-8.09, 11.28) 0.870 Number of embryos transferred, n, mean (± SD) 1.78 ± 0.44 1.90 ± 0.30 1.73 ± 0.45 1.74 ± 0.48 0.248 Grade of transferred embryos High-score embryo, number/total transferred embryos (%) 13/16 (81.25%) 72/78 (92.31%) 44/52 (84.62%) 94/101 (93.07%) 0.199 Low-score embryo, number/total transferred embryos (%) 3/16 (18.75%) 6/78 (7.69%) 8/52 (15.38%) 7/101 (6.93%) Table 2 Characteristics of hormone replacement treatment FET cycles with 4 type of endometrial patterns on blastocyst transfer day A (n = 21) B (n = 120) B-C (n = 134) C (n = 286) P value Age, years, mean (± SD) 31.05 ± 4.88 31.36 ± 4.47 30.98 ± 4.4 32.1 ± 4.91 0.103 BMI, kg/m2, mean (± SD) 24.33 ± 3.48 23.56 ± 3.86 23.33 ± 3.8 23.97 ± 3.93 0.347 Duration of infertility, years, median (25 th , 75 th percentile) 2.00 (1.00, 3.75) 3.00 (1.50, 4.00) 3.00 (2.00, 4.50) 3.00 (2.00, 5.00) 0.059 Infertility type Primary infertility, n (%) 13 (61.90%) 68 (56.67%) 76 (56.72%) 160 (55.94%) 0.962 Secondary infertility, n (%) 8 (38.10%) 52 (43.44%) 58 (43.28%) 126 (44.06%) Endometrial preparation protocol HRT 16 (76.19%) 89 (74.17%) 108 (80.60%) 204 (71.33%) 0.246 GnRHa-HRT 5 (23.81%) 31 (25.83%) 26 (19.40%) 82 (28.67%) The day of endometrial transformation Endometrial thickness, mm, mean (± SD) 9.49 ± 1.53 10.27 ± 2.01 10.27 ± 1.83 10.08 ± 1.89 0.260 Serum estrogen level, pmol/L, median (25 th , 75 th percentile) 1554.0 (742.0, 3098.0) 1697.5 (1057.5, 2712.5) 1560.5 (1069.0, 2838.0) 2067.0 (1168.0, 5606.0) 0.042 Serum progesterone level, pmol/L, median (25 th , 75 th percentile) 1.28 (1.06, 2.25) 1.26 (0.61, 1.88) 1.36 (0.73, 1.80) 1.15 (0.66, 1.81) 0.335 The day of embryo transfer Endometrial thickness, mm, mean (± SD) 11.02 ± 3.83 11.33 ± 2.84 10.89 ± 2.55 10.37 ± 2.56 0.007 Serum estrogen level, pmol/L, median (25 th , 75 th percentile) 1203.0 (748.0, 2051.0) 1562.5 (1009.5, 2342.5) 1688.5 (1291.0, 2258.0) 1725.5 (1179.0, 2385.0 ) 0.068 Serum progesterone level, pmol/L, median (25 th , 75 th percentile) 26.18 (18.21, 30.83) 27.44 (21.03, 31.63) 27.5 (21.21, 33.91) 28.83 (21.36, 35.25) 0.103 The increase percentage of endometrial thickness on embryo transfer day compared with endometrial transformation day (%) 7.22 (0.00, 23.75) 7.96 (-5.53, 26.72) 4.07 (-6.60, 17.05) 2.41 (-10.00, 14.85) 0.019 Number of embryos transferred, n, mean (± SD) 1.24 ± 0.44 1.18 ± 0.38 1.16 ± 0.37 1.14 ± 0.35 0.624 Grade of transferred embryos High-score embryo, number/total transferred embryos (%) 23/26 (88.46%) 131/141(92.91%) 144/156 (92.31%) 287/326 (88.04%) 0.290 Low-score embryo, number/total transferred embryos (%) 3/26 (11.54%) 10/141(7.09%) 12/156 (7.69%) 39/326 (11.96%) Pregnancy outcomes The embryo implantation rate ( p = 0.066), clinical pregnancy rate ( p = 0.140), early abortion rate ( p = 0.515) and live birth rate ( p = 0.578) were similar between the 4 type of endometrial pattern groups in cleavage-stage embryo cycles (Table 3 ). In blastocyst cycles (Table 4 ), the implantation rate ( p = 0.201), clinical pregnancy rate ( p = 0.555) did not differ between the four endometrial patterns. Patients with a Pattern A endometrium on blastocyst transfer day experienced a decreased live birth rate (19.05%) compared with Pattern B, Pattern B-C and Pattern C ( p = 0.006. p = 0.008, p = 0.031 for Pattern A vs . Pattern B, Pattern A vs . Pattern B-C, Pattern A vs . Pattern C). The first trimester abortion rate of Pattern A is 40.00%, which is abnormally higher than normal population. Table 3 Clinical outcomes of hormone replacement treatment FET cycles with 4 type of endometrial patterns on cleavage-stage embryo transfer day A (n = 9) B (n = 41) B-C (n = 30) C (n = 58) P value Implantation, number of gestation sac/total transferred embryos (%) 5/16 (31.25%) 37/78 (47.44%) 17/52 (32.69%) 29/101 (28.71%) 0.066 Clinical pregnancy, n (%) 3 (33.33%) 26 (63.41%) 13 (43.33%) 25 (43.1%) 0.140 Early miscarriage rate, n (%) 0 (0.00%) 4 (15.38%) 0 (0.00%) 4 (16%) 0.515 Live birth rate, n (%) 3 (33.33%) 20 (48.78%) 11 (36.67%) 21 (36.21%) 0.578 Table 4 Clinical outcomes of hormone replacement treatment FET cycles with 4 type of endometrial patterns on blastocyst transfer day A (n = 21) B (n = 120) B-C (n = 134) C (n = 286) P value Implantation, number of gestation sac/total transferred embryos (%) 10/26 (38.46%) 82/141 (58.16%) 91/156 (58.33%) 173/326 (53.07%) 0.201 Clinical pregnancy, n (%) 10 (47.62%) 73 (60.83%) 82 (61.19%) 162 (56.64%) 0.555 Early miscarriage rate, n (%) 4 (40.00%) 8 (10.96%) 12 (14.63%) 25 (15.43%) 0.118 Live birth rate, n (%) 4 (19.05%) 62 (51.67%) 67 (50.00%) 123 (43.01%) 0.023 Endometrial pattern of Pattern A was defined as trilinear type group and Pattern B, B-C, C were gathered as not trilinear type group. The pregnant outcomes of blastocyst cycles were demonstrated in Fig. 3 . In univariate analysis for blastocyst cycles (Table 5 ), the not trilinear group had a similar proportion of biochemical pregnancy (0.695 [95% CI, 0.290–0.414]; p = 0.414) and clinical pregancy (0.640 [95% CI, 0.267–1.532]; p = 0.316) compared with trilinear type endometrium group. In the cycles of not trilinear type group, the early miscarriage rate (0.248 [95% CI, 0.067–0.914]; p = 0.036) was lower and the live birth rate (0.269 [95% CI, 0.089–0.810]; p = 0.020) was higher than trilinear type group. Table 5 Univariate analysis of clinical outcome in blastocyst FET cycles with hormone replacement treatment Factors OR 95% CL P value Biochemical pregnancy rate, n (%) Trilinear 11/21 (52.38%) Reference 0.414 Not trilinear 331/540 (61.30%) 0.695 0.290–1.664 Clinical pregnancy rate, n (%) Trilinear 10 /21(47.62%) Reference 0.316 Not trilinear 317/540 (58.70%) 0.640 0.267–1.532 Early miscarriage rate, n (%) Trilinear 4 (40.00%) Reference 0.036 Not trilinear 45 (14.20%) 0.248 0.067–0.914 Live birth rate, n (%) Trilinear 4 (19.05%) Reference 0.020 Not trilinear 252 (46.67%) 0.269 0.089–0.810 Potential factors for the endometrial morphological patterns on blastocyst transfer day Univariate analysis showed that that female age, BMI, duration of infertility, infertility type, endometrial preparation protocol were not related to the endometrial morphological patterns. Higher serum progesterone level on the day of endometrial transformation (1.506 [95% CI, 0.089–0.810]; p = 0.020) and lower serum estrogen level on the day of embryo transfer (0.999 [95% CI, 0.999–1.000]; p = 0.024) were related to the occurrence of triple line endometrium on blastocyst transfer day (Table 6 ). Table 6 Univariate analysis of endometrial pattern type on blastocyst transfer day in hormone replacement treatment FET cycles Factors OR 95% CL P value Female age 0.972 0.882–1.070 0.559 Female BMI 1.039 0.935–1.154 0.478 Duration of infertility 0.766 0.586–1.003 0.052 Infertility type Primary infertility Reference 0.105 Secondary infertility 2.102 0.857–5.155 Endometrial preparation protocol HRT Reference 0.843 GnRHa-HRT 0.902 0.324–2.506 Serum estrogen level on the day of endometrial transformation 1.000 1.000–1.000 0.185 Serum progesterone level on the day of endometrial transformation 1.506 1.043–2.175 0.029 Serum estrogen level on the day of embryo transfer 0.999 0.999−1.000 0.024 Serum progesterone level on the day of embryo transfer 0.966 0.924–1.010 0.132 Discussion Appropriate clinical interventions can optimize endometrial receptivity, achieving an ideal conception state and a successful pregnancy outcome. Endometrial receptivity evaluation involves various methods, including endometrial biopsy, magnetic resonance imaging (MRI), and ultrasound. An endometrial biopsy permits examination of the endometrium at the histological level [ 23 ], yet it is an invasive technique with a notable incidence of complications, leading to limited acceptance in clinical practice. MRI offers advantages in delineating endometrial thickness and its relation to the myometrium [ 24 ]; however, this method is costly and time-intensive. Ultrasound, prevalent in clinical practice due to its convenience, non-invasiveness, and affordability, is frequently utilized. Research indicates that endometrial thickness might serve as a proxy for endometrial receptivity [ 25 ]. Nevertheless, the utility of the endometrial echo pattern remains a topic of debate as a predictor for endometrial receptivity. Endometrial echo patterns are identified by comparing the echogenicity of the endometrium with that of the myometrium and by noting a central echogenic line within the endometrium [ 22 , 26 , 27 ]. The echo pattern serves as an ultrasonic index reflecting endometrial proliferation and/or stromal decidualization. In 2019, Laurentiu Craciunas et al. conducted systematic meta-analyses to evaluate the evidence from observational studies regarding the use of endometrial receptivity markers as prognostic factors for pregnancy outcomes[ 1 ]. The study concluded that triple line patterns, assessed on the day of hCG injection in IUI, were linked to higher clinical pregnancy rates. However, the endometrial echo pattern on the hCG injection day/embryo transfer day in women undergoing IVF with fresh embryo transfer, or on the day of progesterone supplementation in FET, showed no significant impact on clinical outcomes. However, this conclusion was analyzed from studies with various ovarian stimulation protocols, different embryos transfer numbers and strategies [ 8 , 18 , 28 , 29 ]. Regarding whether the morphology of the endometrium on embryo transfer day (middle luteal phase) impacts clinical outcomes, we posit that the fresh embryo transfer cycle is not an ideal subject of study. The endometrium, a dynamic tissue, undergoes complex physiological changes in response to ovarian steroid hormones [ 30 ]. Various ovulation-inducing treatments lead to significant hormonal fluctuations, which may influence endometrial morphology, complicating classification and discussion. In this study, we analyze HRT cycles with or without GnRHa treatment to eliminate the effects of exogenous or endogenous gonadotrophins. Between 2020 and 2021, HRT and GnRHa-HRT were our primary endometrial preparation protocols, with clinicians not selectively assigning these two protocols to patients. Moreover, our study excluded patients with moderate or severe endometriosis or adenomyosis. The proportion of these 2 protocols in the 4 types of the endometrium were similar (Table 1 , 2 ), and did not affect the live birth rate (Supplementary Table 1). In cleavage stage embryo FET cycles, the embryo implantation rate, clinical pregnancy rate, early miscarriage rate, and live birth rate were similar in 4 groups and showed no association with endometrial morphology. Regarding the blastocyst cycles, a significant decrease in the live birth rate was observed in the Pattern A group (19.05%), compared with Pattern B (51.67%), Pattern B-C (50.00%), and Pattern C (43.01%) ( p = 0.023). Univariate analysis indicated that a triple line endometrium on the embryo transfer day was associated with a higher first trimester abortion rate and a lower live birth rate. Within the 10 clinically pregnant cases in the Pattern A group, 6 women did not achieve a live birth. 4 women experienced first trimester abortions, with 3 undergoing villus tissue analysis, all yielding euploid results. 1 woman had an ectopic pregnancy, marking her second ectopic pregnancy post-embryo transfer. Another woman underwent induced labor due to abnormal fetal development. Through the analysis of the total data and individual abnormal pregnancy cases, we conclude that a trilaminar endometrium on the day of blastocyst transfer is associated with early pregnancy loss. This may be attributed to inadequate decidualization, resulting in trophoblast cell failure to continue invasion and development. Within hormone replacement transplantation cycles, estrogen and progesterone are sequentially administered to synchronize embryo transfer with the endometrial window of implantation [ 31 ]. In cleavage stage embryo FET cycles, serum estrogen and progesterone levels on both the endometrial transformation day and embryo transfer day were similar across the four endometrial morphological types. In blastocyst transfer cycles, serum estrogen levels on endometrial transformation day in the Pattern C group were higher than those in the other three groups. Univariate analysis indicated that higher serum progesterone levels on the day of endometrial transformation and lower serum estrogen levels on the day of embryo transfer were associated with the occurrence of a triple line endometrium on the day of blastocyst transfer. Progesterone is crucial for the transformation of endometrial cells. However, in this context, it seems challenging to clarify the significance of the minute progesterone changes at the molecular/clinical level in terms of endometrial morphology transformation. We posit that estrogen plays a significant role in the transformation of the endometrium. The purpose of estrogen priming and the achievement of endometrial proliferation is to induce progesterone receptors, which enable subsequent progesterone stimulation to promote endometrial receptivity. Estrogenic stimulation may significantly affect the subsequent luteal phase, and the luteal progression of the endometrium depends not only on the duration and intensity of progesterone stimulation but also on prior estrogen priming. From 2020 to the present, we have collected two samples from the fifth day post-ovulation, where ultrasound indicated an endometrium of Pattern A. We conducted ER and PR testing on these two samples alongside other Pattern C endometrial samples (Supplementary Fig. 2). Due to the limited number of samples, quantitative analysis was not feasible; however, we observed an intriguing case where ERa predominantly expressed in the cytoplasm, rather than in the nucleus. These findings suggest that the morphologically untransformed endometrium of mid-luteal phase may be closely related to aberrant estrogen pathway. We also notice the endometrial compaction, which refers to the decrease in endometrial thickness on the day of embryo transfer compared to the starting day of progesterone administration [ 32 , 33 ]. With the endometrium transformed from trilinear pattern to homogeneous hyperechogenic style, the endometrial compaction was increased, which was consistent with the viewpoint that endometrial compaction was associated with the sustained pregnancy. Unlike the measurement of endometrial thickness, the assessment of endometrial echo possesses a degree of subjectivity. In Julian A's 2015 study, within 180 FET cycles, the endometrial types on blastocyst transfer day were classified as 14 type 2 and 166 type 3, with no type 1 endometrium observed. This could be related to medication methods or ethnic demographics, but it is most likely associated with the subjectivity of the ultrasound physicians. Endometrial pattern is the most crucial observational indicator in our article. Each image was evaluated by the same two doctors, ensuring more stable interpretation. However, this also suggests that if we wish to use endometrial echo pattern as a primary clinical judgment criterion, we should establish a more detailed evaluation system. Artificial intelligence and digitalization are areas that need our attention in the future. A univariate analysis of 540 blastocyst FET cycles was conducted to identify key factors influencing live birth rates (Supplementary Table 1). Consistent with previous studies, female age, BMI, and the number and grades of transferred embryos were associated with live birth rates. We also noted that an endometrium without a triple line was a critical factor affecting live birth rates. However, among the 540 blastocyst transfer cycles, only 19 cases exhibited untransformed endometrium, a very low detection rate (3.74%). Therefore, the necessity of incorporating endometrial echo measurement on the day of transfer into routine clinical practice remains to be considered. Nonetheless, it is necessary to consider this parameter as an important evaluation criterion for populations with recurrent pregnancy loss. It is reasonable to cancel the embryo transfer plan when a trilinear pattern endometrium occurs on the day of blastocyst transfer in FET cycles, especially if the embryo is precious or the patient has had an adverse pregnancy history. If patients have previously experienced mid-luteal phase endometrial non-transformation, we can increase the dosage and method of estrogen administration, or switch to alternative endometrial preparation protocols in subsequent treatment cycles. Conclusions In this manuscript, we discussed the endometrial morphology on cleavage-stage and blastocyst in hormone replacement therapy FET cycle. Our retrospective study suggested that a trilinear pattern endometrium on blastocyst transfer was associated with a higher first trimester abortion rate and lower live birth rate. Estrogen and estrogen receptor may play a significant role in the transformation failure of the endometrium. It is reasonable to cancel the embryo transfer plan when a trilinear pattern endometrium occurs on the day of blastocyst transfer in hormone replacement therapy FET cycles, especially if the embryo is precious or the patient has had an adverse pregnancy history. Declarations Ethics approval and consent to participate This study received ethical approval by the Clinical Ethics Review Committee of Nanjing Jinling Hospital. All methods were carried out in accordance with relevant guidelines and regulations. The informed consent was waived by the same ethics committee that approved the study (the ethics committee of Nanjing Jinling Hospital) due to the retrospective nature. The patients underwent endometrial biopsy examination for medical purpose. Informed consent forms were signed by study participants. Consent for publication Not applicable. Availability of data and materials All data that support the findings of this study are available from the corresponding author upon reasonable request. Competing interests The authors have declared no conflicts of interest. Funding This work is supported by National Natural Science Foundation of China (Grant: 82101757) and Annual Foundation of Nanjing Jinling Hospital (YYQN2021082, 22LCYY-QH5, 22LCYY-QH12). Each of the funding contributed to expenses related to specific procedures carried out in the project. Authors' contributions Xi Cheng designed the study and contributed to writing the article. Bin Yang and Li Wang contributed to clinical operation and data analysis. Jinzhao Ma and Haiyan Fu contributed to data analysis. Xuan Huang, Cheng Zhou and Tang Xu contributed to clinical operation. Kadiliya Jueraitetibaike contributed to the collection of clinical samples. Li Biying contributed to the molecular experiment. Xiting Cai contributed to the the writing the article. Li Chen and Bing Yao contributed to the study design, data interpretation, as well as article revision. All authors have agreed to be listed and have approved the final article. Acknowledgments We thank the other members of Dr. Yao’s laboratory for their discussion and help. References Craciunas L, Gallos I, Chu J, Bourne T, Quenby S, Brosens JJ, Coomarasamy A. Conventional and modern markers of endometrial receptivity: a systematic review and meta-analysis. Hum Reprod Update. 2019;25(2):202–23. Garratt J, Rahmati M. Assessing the endometrium: An update on current and potential novel biomarkers of receptivity. J Reprod Immunol. 2023;160:104162. Kasius A, Smit JG, Torrance HL, Eijkemans MJC, Mol BW, Opmeer BC, Broekmans FJM. Endometrial thickness and pregnancy rates after IVF: a systematic review and meta-analysis. Hum Reprod Update. 2014;20(4):530–41. Gao G, Cui X, Li S, Ding P, Zhang S, Zhang Y. Endometrial thickness and IVF cycle outcomes: a meta-analysis. Reprod Biomed Online. 2020;40(1):124–33. Dickey RP, Olar TT, Curole DN, Taylor SN, Rye PH. Endometrial pattern and thickness associated with pregnancy outcome after assisted reproduction technologies. Hum Reprod. 1992;7(3):418–21. Oluborode 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(1):166–75. Barker MA, Boehnlein LM, Kovacs P, Lindheim SR. Follicular and luteal phase endometrial thickness and echogenic pattern and pregnancy outcome in oocyte donation cycles. J Assist Reprod Genet. 2009;26(5):243–9. Bassil S. Changes in endometrial thickness, width, length and pattern in predicting pregnancy outcome during ovarian stimulation in in vitro fertilization. Ultrasound Obstet Gynecol. 2001;18(3):258–63. Chen S-L, Wu F-R, Luo C, Chen X, Shi X-Y, Zheng H-Y, Ni Y-P. Combined analysis of endometrial thickness and pattern in predicting outcome of in vitro fertilization and embryo transfer: a retrospective cohort study. Reprod Biol Endocrinol. 2010;8:30. Singh N, Bahadur A, Mittal S, Malhotra N, Bhatt A. Predictive value of endometrial thickness, pattern and sub-endometrial blood flows on the day of hCG by 2D doppler in in-vitro fertilization cycles: A prospective clinical study from a tertiary care unit. J Hum Reprod Sci. 2011;4(1):29–33. Yang W, Zhang T, Li Z, Ren X, Huang B, Zhu G, Jin L. Combined analysis of endometrial thickness and pattern in predicting clinical outcomes of frozen embryo transfer cycles with morphological good-quality blastocyst: A retrospective cohort study. Med (Baltim). 2018;97(2):e9577. Rashidi BH, Sadeghi M, Jafarabadi M, Tehrani Nejad ES. Relationships between pregnancy rates following in vitro fertilization or intracytoplasmic sperm injection and endometrial thickness and pattern. Eur J Obstet Gynecol Reprod Biol. 2005;120(2):179–84. Ahmadi F, Akhbari F, Zamani M, Ramezanali F, Cheraghi R. Value of Endometrial Echopattern at HCG Administration Day in Predicting IVF Outcome. Arch Iran Med. 2017;20(2):101–4. Liao S, Wang R, Hu C, Pan W, Pan W, Yu D, Jin L. Analysis of endometrial thickness patterns and pregnancy outcomes considering 12,991 fresh IVF cycles. BMC Med Inf Decis Mak. 2021;21(1):176. Check JH, Dietterich C, Lurie D. Non-homogeneous hyperechogenic pattern 3 days after embryo transfer is associated with lower pregnancy rates. Hum Reprod. 2000;15(5):1069–74. Check JH, Dietterich C, Nazari A, Lurie D, Choe JK, Check ML. Non-homogeneous hyperechogenic echo pattern three days after frozen embryo transfer is associated with lower pregnancy rates. Clin Exp Obstet Gynecol. 2005;32(1):15–8. Check JH, Gandica R, Dietterich C, Lurie D. Evaluation of a nonhomogeneous endometrial echo pattern in the midluteal phase as a potential factor associated with unexplained infertility. Fertil Steril. 2003;79(3):590–3. Maugey-Laulom B, Commenges-Ducos M, Jullien V, Papaxanthos-Roche A, Scotet V, Commenges D. Endometrial vascularity and ongoing pregnancy after IVF. Eur J Obstet Gynecol Reprod Biol. 2002;104(2):137–43. The Istanbul consensus workshop on embryo. assessment: proceedings of an expert meeting. Hum Reprod 2011, 26(6):1270–1283. Gardner DK, Lane M, Stevens J, Schlenker T, Schoolcraft WB. Blastocyst score affects implantation and pregnancy outcome: towards a single blastocyst transfer. Fertil Steril. 2000;73(6):1155–8. Zhao J, Zhang Q, Wang Y, Li Y. Endometrial pattern, thickness and growth in predicting pregnancy outcome following 3319 IVF cycle. Reprod Biomed Online. 2014;29(3):291–8. Smith B, Porter R, Ahuja K, Craft I. Ultrasonic assessment of endometrial changes in stimulated cycles in an in vitro fertilization and embryo transfer program. J Vitro Fert Embryo Transf. 1984;1(4):233–8. Moustafa S, Young SL. Diagnostic and therapeutic options in recurrent implantation failure. F1000Res 2020, 9. Meylaerts LJ, Wijnen L, Ombelet W, Bazot M, Vandersteen M. Uterine junctional zone thickness in infertile women evaluated by MRI. J Magn Reson Imaging. 2017;45(3):926–36. Bergin K, Eliner Y, Duvall DW, Roger S, Elguero S, Penzias AS, Sakkas D, Vaughan DA. The use of propensity score matching to assess the benefit of the endometrial receptivity analysis in frozen embryo transfers. Fertil Steril. 2021;116(2):396–403. Gonen Y, Casper RF. Prediction of implantation by the sonographic appearance of the endometrium during controlled ovarian stimulation for in vitro fertilization (IVF). J Vitro Fert Embryo Transf. 1990;7(3):146–52. Check JH, Lurie D, Dietterich C, Callan C, Baker A. Adverse effect of a homogeneous hyperechogenic endometrial sonographic pattern, despite adequate endometrial thickness on pregnancy rates following in-vitro fertilization. Hum Reprod. 1993;8(8):1293–6. Sharara FI, Lim J, McClamrock HD. Endometrial pattern on the day of oocyte retrieval is more predictive of implantation success than the pattern or thickness on the day of hCG administration. J Assist Reprod Genet. 1999;16(10):523–8. Puerto B, Creus M, Carmona F, Civico S, Vanrell JA, Balasch J. Ultrasonography as a predictor of embryo implantation after in vitro fertilization: a controlled study. Fertil Steril. 2003;79(4):1015–22. Ruiz-Alonso M, Valbuena D, Gomez C, Cuzzi J, Simon C. Endometrial Receptivity Analysis (ERA): data versus opinions. Hum Reprod Open. 2021;2021(2):hoab011. Owusu-Akyaw A, Krishnamoorthy K, Goldsmith LT, Morelli SS. The role of mesenchymal-epithelial transition in endometrial function. Hum Reprod Update. 2019;25(1):114–33. Zilberberg E, Smith R, Nayot D, Haas J, Meriano J, Barzilay E, Casper RF. Endometrial compaction before frozen euploid embryo transfer improves ongoing pregnancy rates. Fertil Steril. 2020;113(5):990–5. Li Q, Liu A, Shen H, Zhang X. Endometrial compaction after human chorionic gonadotrophin administration reduces ectopic pregnancy rate following fresh embryo transfer in vitro fertilization/intracytoplasmic sperm injection cycles in patients with non-thin endometrium: a retrospective cohort study. Reprod Biol Endocrinol. 2022;20(1):151. Additional Declarations No competing interests reported. Supplementary Files sFig1legand.tif SFig2legand.tif Supplementarytable.docx Cite Share Download PDF Status: Published Journal Publication published 10 Apr, 2025 Read the published version in BMC Pregnancy and Childbirth → Version 1 posted Editorial decision: Revision requested 07 Aug, 2024 Reviews received at journal 02 Aug, 2024 Reviews received at journal 30 Jul, 2024 Reviewers agreed at journal 29 Jul, 2024 Reviewers agreed at journal 19 Jul, 2024 Reviewers invited by journal 23 May, 2024 Editor assigned by journal 17 May, 2024 Editor invited by journal 22 Feb, 2024 Submission checks completed at journal 22 Feb, 2024 First submitted to journal 14 Feb, 2024 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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study\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Fig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3955580/v1/d8ddde77fd8bb932ba85fa22.jpg"},{"id":51566284,"identity":"54e49b81-e898-4f38-afc5-0a9697eec1ec","added_by":"auto","created_at":"2024-02-23 19:11:38","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":782842,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe number and proportion of hormone replacement therapy FET cycles of 4 type of endometrial patterns on embryo transfer day\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Fig2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3955580/v1/49fa527f3cd436fbf9620fe5.jpg"},{"id":51566285,"identity":"316b4f02-ed4b-4f19-8869-dc8a2d85dbba","added_by":"auto","created_at":"2024-02-23 19:11:38","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":925673,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe clinical outcomes of trilinear groups and non-trilinear groups in blastocyst transfer cycles\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Fig3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3955580/v1/d058aacb9d586f23e0189609.jpg"},{"id":80558933,"identity":"aba83ad1-674f-4bef-b279-405bbdbb508d","added_by":"auto","created_at":"2025-04-14 16:17:03","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2289265,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3955580/v1/febb5cc9-6ef1-4a4a-a5b7-34ecad9b9338.pdf"},{"id":51566288,"identity":"ce0088d6-b9e1-4907-96f1-0b9f820bb1b6","added_by":"auto","created_at":"2024-02-23 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19:19:38","extension":"docx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":14616,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementarytable.docx","url":"https://assets-eu.researchsquare.com/files/rs-3955580/v1/16add8ee2ca3232e5522a633.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Endometrial echo patterns of embryo transfer day affect pregnancy outcomes in frozen embryo transfer cycles: a retrospective clinical study","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe success of IVF-ET (\u003cem\u003eIn vitro\u003c/em\u003e fertilization and embryo transfer) relies on a high-quality embryo, a receptive endometrium, and a healthy maternal condition. The endometrium, undergoing a series of structural and biochemical changes during the reproductive cycle, must be in a receptive phase [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. For decades, reproductive scientists have worked diligently to identify a suitable method for assessing endometrial receptivity. Currently, transvaginal ultrasonography is the most widely used in clinical practice, which provided clinicians with a non-invasive approach for monitoring endometrial development throughout the menstrual cycle.\u003c/p\u003e \u003cp\u003eEndometrial thickness and echo pattern are the most commonly used markers for evaluating endometrial receptivity in transvaginal ultrasonography examine. Numerous studies suggest that endometrial thickness is an independent predictor of pregnancy occurrence [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Regarding the endometrial echo pattern, however, consensus is lacking in clinical application.\u003c/p\u003e \u003cp\u003eEndometrial echo patterns observed sonographically are categorized as triple line (TL), appearing multilayered with hyperechogenic outer walls and a distinct central echogenic line; isoechogenic (IE), where the endometrium exhibits the same echogenicity as the myometrium with a poorly defined central echogenic line; and homogeneous hyperechogenic (HH), presenting as an entirely echodense endometrium, more echogenic than the myometrium without a visible central echogenic line [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The endometrium transitions from a triple line pattern to a non-triple line pattern in the natural cycle under the action of steroid hormones. Currently, there exists controversy over whether echo patterns are associated with clinical outcomes. Previous research predominantly focused on the late proliferative phase in ovarian stimulation cycles. Some studies reported that endometrial pattern on the day of hCG injection or progesterone administration was not associated with pregnancy outcomes in ART [\u003cspan additionalcitationids=\"CR7 CR8 CR9 CR10 CR11\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e], while some studies reported higher pregnancy rates among women with trilinear endometrial pattern, compared to those with semitrilinear or unilinear endometrial patterns [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRegarding the secretory phase, J H Check et al. observed decreased pregnancy and implantation rates in cycles where the homogeneous hyperechogenic pattern did not occur three days after transfer[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. A nonhomogeneous endometrial echo pattern in the midluteal phase was identified as a potential factor in unexplained infertility [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. However, some studies reported that the endometrial pattern on the day of D2/D3 embryo transfer was not associated with pregnancy outcomes in IVF-ET cycles [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn assisted reproduction treatment, clinicians pay close attention to endometrial thickness and pattern in the proliferative phase. Embryo implantation is rarely canceled due to endometrial factors after endometrial transformation. However, whether the endometrial pattern on embryo transfer day affects pregnancy outcomes remains unclear. In this manuscript, we conducted a retrospective analysis of 699 FET cycles at our reproductive medicine center. We selected FET cycles using an exogenous estrogen and progesterone protocol to minimize variables potentially affecting the endometrium in each cycle. The study's objective was to thoroughly assess the relationship between the sonographic endometrial pattern on embryo transfer day and pregnancy outcomes in women undergoing hormonally prepared FET cycles.\u003c/p\u003e"},{"header":"Methods and materials","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003ePatients and study design\u003c/h2\u003e \u003cp\u003eWe conducted a retrospective cohort study, collecting data from the electronic records of women who underwent FET cycles (more than one cycle per patient) via hormone replacement treatment with or without GnRHa from July 2020 to August 2021 at the Reproduction Medicine Center of Jinling Hospital, Medical College of Nanjing University (Nanjing, China). The exclusion criteria were: (a) age over 44 years; (b) coexisting hydrosalpinx, endometrial lesions, or an abnormal uterine environment (uterine fibroids protruding into the uterine cavity, submucosal fibroids, uterine adhesions, etc.); (c) uterine anomalies; (d) moderate or severe endometriosis or adenomyosis. Patients underwent no therapeutic interventions apart from routine procedures. Monitoring and management followed the standardized clinical protocols of the hospital. The embryos at the cleavage stage were evaluated according to the Istanbul consensus [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Cleavage-stage (D3) high-quality embryos were defined as having 6\u0026ndash;10 cells, with fragments\u0026thinsp;\u0026lt;\u0026thinsp;30% and no severe asymmetry. Blastocysts were assessed on D5-D7 based on the criteria of Gardner [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Blastocysts with a score higher than 3BB were categorized as high-quality blastocysts.\u003c/p\u003e \u003cp\u003eTransvaginal ultrasound scans (TVUS) were performed on the day of cleavage-stage embryo or blastocyst transfer. All scans were conducted by experienced clinicians, and the images were printed and reviewed by the same two physicians. The endometrial echo pattern was classified into three types [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]: Pattern A, Pattern B, and Pattern C. Pattern A represented a multilayered \"triple-line\" endometrium, consisting of a central hyperechogenic line surrounded by two hypoechoic layers; Pattern B was characterized as an isoechogenic pattern relative to the surrounding myometrium with an unclear central hyperechogenic line; Pattern C displayed a homogeneous, hyperechogenic endometrium with increased reflectivity compared to the myometrium. An intermediate pattern B-C featured a gradual increase in reflectivity from the peripheral region to the central line. Endometrium of Pattern A was defined as trilinear type, and endometrium of Pattern B, B-C and C were defined as not trilinear type. Images of the four endometrial patterns are presented in Supplementary Fig.\u0026nbsp;1.\u003c/p\u003e \u003cp\u003eThe outcomes measured included embryo implantation rate, clinical pregnancy rate, first trimester abortion rate, and live birth rate. Pregnancy outcomes were followed up by phone and recorded in our electronic medical record. All data were collected using an exclusive internal database at our reproductive medicine center, ensuring patient data security through advanced threat prevention and periodic password renewals for user access. The methodological pipeline is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe endometria specimen demonstrated in this manuscript were collected on the 5th day after ovulation. The study procedures were approved by the Clinical Ethics Review Committee of Nanjing Jinling Hospital.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eEndometrial preparation and embryo transfer\u003c/h2\u003e \u003cp\u003eIn the early stages of menstruation (between the second and fourth day of the menstrual cycle), patients underwent a sex hormone serum test and transvaginal ultrasonography examination. If GnRHa-HRT protocol was applied, 3.75 mg of triptorelin acetate (Ipsen Pharma Biotech) was administered on the the second and fourth day of the menstrual cycle, a sex hormone serum test and transvaginal ultrasonography examination were applied 28\u0026ndash;35 days later. Those without abnormalities commenced oral intake of a fixed dose of exogenous estradiol for 10\u0026ndash;16 days (Femoston, 4 mg b.i.d.). Serum E2 and P levels, along with endometrial thickness, were monitored to exclude premature ovulation. Patients with low endometrial thickness received additional vaginal medication (Femoston, 2 mg estradiol q.d.). Upon achieving the requisite endometrial thickness (\u0026ge;\u0026thinsp;8 mm), oral estradiol was combined with dydrogesterone compound tablets (Femoston, 4 mg estradiol and 20 mg dydrogesterone b.i.d. \u0026times; 4 or 6 days), supplemented with a vaginal progesterone soft capsule (Utrogestan, 400mg b.i.d.) to induce endometrial transformation. Cleavage-stage embryos were thawed and transferred on the fifth day of endometrial transformation, and blastocysts on the seventh day. TVUS assessed the endometrial thickness and echo pattern, and serum E2 and P levels were measured on the embryo transfer day. For luteal support, patients typically continued Femoston (4 mg estradiol and 20 mg dydrogesterone, b.i.d.) and vaginal progesterone soft capsule (Utrogestan, 400mg b.i.d.). Serum β-human chorionic gonadotropin (β-hCG) was detected 2 weeks post-embryo transfer to determine biochemical pregnancies. Transvaginal ultrasound was performed 4 weeks post-embryo transfer in patients with positive β-hCG results to confirm clinical pregnancies and the number of implanted embryos. A clinical pregnancy was identified by the presence of a gestational sac. Luteal support in pregnant patients was sustained until 2 months post-embryo transfer. Follow-up was conducted to detect abnormalities during pregnancy. Early miscarriage was defined as spontaneous abortion occurring before 12 weeks of pregnancy. Live birth was defined as the delivery of a living newborn after the 28th gestational week, with live birth rate calculated as the ratio of live birth cycle number to the number of embryo transfer cycles.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eImmunohistochemistry staining\u003c/h2\u003e \u003cp\u003eThe endometrial samples were fixed in neutral buffered formalin (NBF). Following deparaffinization and rehydration, the sections were subjected to antigen retrieval. Afterward, the sections were incubated with primary antibody of antibodies against Estrogen receptor α (DAKO), Estrogen receptor β (Abcam) or Progesterone receptor (DAKO) overnight at 4\u0026deg;C. Subsequently, the slides were incubated with secondary antibody at room temperature. Haematoxylin was used to counterstain the sections.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eSPSS 26.0 (SPSS Inc., Chicago, IL, USA) software was used for statistical analysis. Chi-square testing was introduced for analysis, supported by Fisher's exact test with Monte Carlo simulation for expected cell frequencies below five. Measurement data are assessed for normality using histograms. Data fitting the normal distribution are depicted as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation and analyzed with one-way ANOVA to compare group differences. For non-normal distributions, data are shown as medians (interquartile ranges) and analyzed by the Kruskal-Wallis H test. Univariate analysis was used to preliminarily evaluate variables related to the clinical pregnancy outcome, and a multivariable logistic regression model was further employed to analyze the effect of endometrial echo patterns of embryo transfer day in HRT cycles on the clinical pregnancy outcome. Odds ratio (OR) and 95% confidence intervals (95% CI) were estimated using logistic regression. P\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eCharacteristics of all FET cycles\u003c/h2\u003e \u003cp\u003eThis study involved 699 HRT-FET cycles, including 159 cleavage stage embryo transfer cycles and 540 blastocyst transfer cycles. Transvaginal ultrasound scans were conducted on embryo transfer day, 1 to 3 hours before transfer operation. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, in cleavage-stage embryo cycles, 9 (6.50%) cycles were pattern A, 41 (29.7%) cycles were pattern B, 30 (21.7%) cycles were pattern B-C and 58 (42.0%) cycles were pattern C. In blastocyst cycles, 21 (3.74%) cycles were pattern A, 120 (21.39%) cycles were pattern B, 134 (23.89%) cycles were pattern B-C and 286 (50.98%) cycles w` ere pattern C.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe demographic characteristics, the numbers and scores of embryos transferred are showed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e2\u003c/span\u003e. No significant differences were noted between the groups regarding the female age, the body mass index (BMI), infertility type, infertility duration, the endometrial thickness on progesterone administration day, the number and grade of transferred embryos both in cleavage-stage embryo and blastocyst transfer cycles. Cycles with Pattern C endometrial patterns had a relatively thinner endometrial thickness on blastocyst transfer day compared with Pattern B group (10.37\u0026thinsp;\u0026plusmn;\u0026thinsp;2.56 mm \u003cem\u003evs\u003c/em\u003e. 11.33\u0026thinsp;\u0026plusmn;\u0026thinsp;2.84mm; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.006). Cycles with Pattern C endometrial patterns had a higher serum estrogen level on endometrial transformation day compared with Pattern B-C group (1560.5 [1069.0-2838.0] pmol/L vs. 2067.0 [1168.0-5606.0] pmol/L; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.037).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCharacteristics of hormone replacement treatment FET cycles with 4 type of endometrial patterns on cleavage-stage embryo transfer day\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA (n\u0026thinsp;=\u0026thinsp;9)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eB (n\u0026thinsp;=\u0026thinsp;41)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eB-C (n\u0026thinsp;=\u0026thinsp;30)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eC (n\u0026thinsp;=\u0026thinsp;58)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge, years, mean (\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e35.44\u0026thinsp;\u0026plusmn;\u0026thinsp;7.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e31.39\u0026thinsp;\u0026plusmn;\u0026thinsp;5.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e34.4\u0026thinsp;\u0026plusmn;\u0026thinsp;7.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e34.38\u0026thinsp;\u0026plusmn;\u0026thinsp;6.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.076\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI, kg/m2, mean (\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e22.49\u0026thinsp;\u0026plusmn;\u0026thinsp;2.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22.76\u0026thinsp;\u0026plusmn;\u0026thinsp;3.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e24.33\u0026thinsp;\u0026plusmn;\u0026thinsp;3.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e23.84\u0026thinsp;\u0026plusmn;\u0026thinsp;3.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.169\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDuration of infertility, years, median (25\u003csup\u003eth\u003c/sup\u003e, 75\u003csup\u003eth\u003c/sup\u003e percentile)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.00 (1.50, 7.75)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.00 (2.00, 4.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.50 (1.50, 4.13)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.00 (2.00, 5.13)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.528\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003eInfertility type\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePrimary infertility, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4 (44.44%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25 (60.98%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e17 (56.67%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e30 (51.72%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.733\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSecondary infertility, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 (55.56%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e16 (30.02%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e13 (43.33%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e28 (48.28%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003eEndometrial preparation protocol\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHRT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6 (66.67%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e31 (75.61%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e22 (73.33%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e33 (56.90%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.206\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGnRHa-HRT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3 (33.33%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10 (24.39%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8 (26.67%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e25 (43.10%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe day of endometrial transformation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEndometrial thickness, mm, mean (\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.37\u0026thinsp;\u0026plusmn;\u0026thinsp;1.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.36\u0026thinsp;\u0026plusmn;\u0026thinsp;1.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.26\u0026thinsp;\u0026plusmn;\u0026thinsp;2.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.58\u0026thinsp;\u0026plusmn;\u0026thinsp;2.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.432\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum estrogen level, pmol/L, median (25\u003csup\u003eth\u003c/sup\u003e, 75\u003csup\u003eth\u003c/sup\u003e percentile)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1971.0 (1594.0, 2072.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1999.0 (1372.0, 5406.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1738.0 (1178.0, 2750.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2050.0 (1228.0, 6570.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.740\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum progesterone level, pmol/L, median (25\u003csup\u003eth\u003c/sup\u003e, 75\u003csup\u003eth\u003c/sup\u003e percentile)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.37 (1.08, 1.69)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.42 (0.66, 1.89)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.44 (0.83, 2.16)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.05 (0.80, 1.62)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.417\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003eThe day of embryo transfer\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEndometrial thickness, mm, mean (\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.06\u0026thinsp;\u0026plusmn;\u0026thinsp;2.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.93\u0026thinsp;\u0026plusmn;\u0026thinsp;3.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.97\u0026thinsp;\u0026plusmn;\u0026thinsp;2.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.675\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum estrogen level, pmol/L, median (25\u003csup\u003eth\u003c/sup\u003e, 75\u003csup\u003eth\u003c/sup\u003e percentile)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1680.0 (1441.0, 2284.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1659.0 (1062.0, 2276.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1695.5 (1196.0, 2268.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1714.5 (1109.0, 2540.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.811\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum progesterone level, pmol/L, median (25\u003csup\u003eth\u003c/sup\u003e \u0026ndash; 75\u003csup\u003eth\u003c/sup\u003e percentile)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25.05 (23.06, 26.88)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26.46 (19.92, 33.42)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e32.71 (26.31, 39.23)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e29.81 (22.84, 36.11)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.167\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe increase percentage of endometrial thickness on embryo transfer day compared with endometrial transformation day (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.88 (1.22, 19.77)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.83 (-6.31, 15.79)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.15 (-10.64, 15.91)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5.39 (-8.09, 11.28)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.870\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNumber of embryos transferred, n, mean (\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.78\u0026thinsp;\u0026plusmn;\u0026thinsp;0.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.90\u0026thinsp;\u0026plusmn;\u0026thinsp;0.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.73\u0026thinsp;\u0026plusmn;\u0026thinsp;0.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.74\u0026thinsp;\u0026plusmn;\u0026thinsp;0.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.248\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003eGrade of transferred embryos\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHigh-score embryo, number/total transferred embryos (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13/16 (81.25%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e72/78 (92.31%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e44/52 (84.62%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e94/101 (93.07%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.199\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLow-score embryo, number/total transferred embryos (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3/16 (18.75%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6/78 (7.69%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8/52 (15.38%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7/101 (6.93%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCharacteristics of hormone replacement treatment FET cycles with 4 type of endometrial patterns on blastocyst transfer day\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA (n\u0026thinsp;=\u0026thinsp;21)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eB (n\u0026thinsp;=\u0026thinsp;120)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eB-C (n\u0026thinsp;=\u0026thinsp;134)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eC (n\u0026thinsp;=\u0026thinsp;286)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge, years, mean (\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e31.05\u0026thinsp;\u0026plusmn;\u0026thinsp;4.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e31.36\u0026thinsp;\u0026plusmn;\u0026thinsp;4.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e30.98\u0026thinsp;\u0026plusmn;\u0026thinsp;4.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e32.1\u0026thinsp;\u0026plusmn;\u0026thinsp;4.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.103\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI, kg/m2, mean (\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24.33\u0026thinsp;\u0026plusmn;\u0026thinsp;3.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23.56\u0026thinsp;\u0026plusmn;\u0026thinsp;3.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e23.33\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e23.97\u0026thinsp;\u0026plusmn;\u0026thinsp;3.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.347\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDuration of infertility, years, median (25\u003csup\u003eth\u003c/sup\u003e, 75\u003csup\u003eth\u003c/sup\u003e percentile)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.00 (1.00, 3.75)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.00 (1.50, 4.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.00 (2.00, 4.50)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.00 (2.00, 5.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.059\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003eInfertility type\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePrimary infertility, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13 (61.90%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e68 (56.67%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e76 (56.72%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e160 (55.94%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.962\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSecondary infertility, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8 (38.10%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e52 (43.44%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e58 (43.28%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e126 (44.06%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003eEndometrial preparation protocol\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHRT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16 (76.19%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e89 (74.17%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e108 (80.60%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e204 (71.33%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.246\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGnRHa-HRT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 (23.81%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e31 (25.83%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e26 (19.40%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e82 (28.67%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003eThe day of endometrial transformation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEndometrial thickness, mm, mean (\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.49\u0026thinsp;\u0026plusmn;\u0026thinsp;1.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.27\u0026thinsp;\u0026plusmn;\u0026thinsp;2.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.27\u0026thinsp;\u0026plusmn;\u0026thinsp;1.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.08\u0026thinsp;\u0026plusmn;\u0026thinsp;1.89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.260\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum estrogen level, pmol/L, median (25\u003csup\u003eth\u003c/sup\u003e, 75\u003csup\u003eth\u003c/sup\u003e percentile)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1554.0 (742.0, 3098.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1697.5 (1057.5, 2712.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1560.5 (1069.0, 2838.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2067.0 (1168.0, 5606.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.042\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum progesterone level, pmol/L, median (25\u003csup\u003eth\u003c/sup\u003e, 75\u003csup\u003eth\u003c/sup\u003e percentile)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.28 (1.06, 2.25)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.26 (0.61, 1.88)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.36 (0.73, 1.80)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.15 (0.66, 1.81)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.335\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003eThe day of embryo transfer\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEndometrial thickness, mm, mean (\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11.02\u0026thinsp;\u0026plusmn;\u0026thinsp;3.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11.33\u0026thinsp;\u0026plusmn;\u0026thinsp;2.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.89\u0026thinsp;\u0026plusmn;\u0026thinsp;2.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.37\u0026thinsp;\u0026plusmn;\u0026thinsp;2.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.007\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum estrogen level, pmol/L, median (25\u003csup\u003eth\u003c/sup\u003e, 75\u003csup\u003eth\u003c/sup\u003e percentile)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1203.0 (748.0, 2051.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1562.5 (1009.5, 2342.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1688.5 (1291.0, 2258.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1725.5 (1179.0, 2385.0 )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.068\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum progesterone level, pmol/L, median (25\u003csup\u003eth\u003c/sup\u003e, 75\u003csup\u003eth\u003c/sup\u003e percentile)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e26.18 (18.21, 30.83)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e27.44 (21.03, 31.63)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e27.5 (21.21, 33.91)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e28.83 (21.36, 35.25)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.103\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe increase percentage of endometrial thickness on embryo transfer day compared with endometrial transformation day (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.22 (0.00, 23.75)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.96 (-5.53, 26.72)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.07 (-6.60, 17.05)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.41 (-10.00, 14.85)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.019\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNumber of embryos transferred, n, mean (\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.24\u0026thinsp;\u0026plusmn;\u0026thinsp;0.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.18\u0026thinsp;\u0026plusmn;\u0026thinsp;0.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.14\u0026thinsp;\u0026plusmn;\u0026thinsp;0.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.624\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003eGrade of transferred embryos\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHigh-score embryo, number/total transferred embryos (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e23/26 (88.46%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e131/141(92.91%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e144/156 (92.31%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e287/326 (88.04%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.290\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLow-score embryo, number/total transferred embryos (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3/26 (11.54%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10/141(7.09%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e12/156 (7.69%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e39/326 (11.96%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003ePregnancy outcomes\u003c/h2\u003e \u003cp\u003eThe embryo implantation rate (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.066), clinical pregnancy rate (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.140), early abortion rate (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.515) and live birth rate (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.578) were similar between the 4 type of endometrial pattern groups in cleavage-stage embryo cycles (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). In blastocyst cycles (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), the implantation rate (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.201), clinical pregnancy rate (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.555) did not differ between the four endometrial patterns. Patients with a Pattern A endometrium on blastocyst transfer day experienced a decreased live birth rate (19.05%) compared with Pattern B, Pattern B-C and Pattern C (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.006. \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.008, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.031 for Pattern A \u003cem\u003evs\u003c/em\u003e. Pattern B, Pattern A \u003cem\u003evs\u003c/em\u003e. Pattern B-C, Pattern A \u003cem\u003evs\u003c/em\u003e. Pattern C). The first trimester abortion rate of Pattern A is 40.00%, which is abnormally higher than normal population.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eClinical outcomes of hormone replacement treatment FET cycles with 4 type of endometrial patterns on cleavage-stage embryo transfer day\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA (n\u0026thinsp;=\u0026thinsp;9)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eB (n\u0026thinsp;=\u0026thinsp;41)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eB-C (n\u0026thinsp;=\u0026thinsp;30)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eC (n\u0026thinsp;=\u0026thinsp;58)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eImplantation, number of gestation sac/total transferred embryos (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5/16 (31.25%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e37/78 (47.44%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e17/52 (32.69%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e29/101 (28.71%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.066\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eClinical pregnancy, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3 (33.33%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e26 (63.41%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e13 (43.33%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e25 (43.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.140\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEarly miscarriage rate, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0 (0.00%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4 (15.38%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0 (0.00%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4 (16%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.515\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLive birth rate, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3 (33.33%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e20 (48.78%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e11 (36.67%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e21 (36.21%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.578\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eClinical outcomes of hormone replacement treatment FET cycles with 4 type of endometrial patterns on blastocyst transfer day\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA (n\u0026thinsp;=\u0026thinsp;21)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eB (n\u0026thinsp;=\u0026thinsp;120)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eB-C (n\u0026thinsp;=\u0026thinsp;134)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eC (n\u0026thinsp;=\u0026thinsp;286)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eImplantation, number of gestation sac/total transferred embryos (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e10/26 (38.46%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e82/141 (58.16%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e91/156 (58.33%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e173/326 (53.07%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.201\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eClinical pregnancy, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e10 (47.62%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e73 (60.83%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e82 (61.19%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e162 (56.64%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.555\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEarly miscarriage rate, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4 (40.00%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8 (10.96%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e12 (14.63%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e25 (15.43%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.118\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLive birth rate, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4 (19.05%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e62 (51.67%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e67 (50.00%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e123 (43.01%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.023\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eEndometrial pattern of Pattern A was defined as trilinear type group and Pattern B, B-C, C were gathered as not trilinear type group. The pregnant outcomes of blastocyst cycles were demonstrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. In univariate analysis for blastocyst cycles (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e), the not trilinear group had a similar proportion of biochemical pregnancy (0.695 [95% CI, 0.290\u0026ndash;0.414]; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.414) and clinical pregancy (0.640 [95% CI, 0.267\u0026ndash;1.532]; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.316) compared with trilinear type endometrium group. In the cycles of not trilinear type group, the early miscarriage rate (0.248 [95% CI, 0.067\u0026ndash;0.914]; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.036) was lower and the live birth rate (0.269 [95% CI, 0.089\u0026ndash;0.810]; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.020) was higher than trilinear type group.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eUnivariate analysis of clinical outcome in blastocyst FET cycles with hormone replacement treatment\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFactors\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e95% CL\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eBiochemical pregnancy rate, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTrilinear\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11/21 (52.38%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.414\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNot trilinear\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e331/540 (61.30%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.695\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.290\u0026ndash;1.664\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eClinical pregnancy rate, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTrilinear\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e10 /21(47.62%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.316\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNot trilinear\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e317/540 (58.70%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.640\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.267\u0026ndash;1.532\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eEarly miscarriage rate, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTrilinear\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4 (40.00%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.036\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNot trilinear\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e45 (14.20%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.248\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.067\u0026ndash;0.914\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eLive birth rate, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTrilinear\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4 (19.05%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.020\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNot trilinear\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e252 (46.67%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.269\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.089\u0026ndash;0.810\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003ePotential factors for the endometrial morphological patterns on blastocyst transfer day\u003c/h2\u003e \u003cp\u003eUnivariate analysis showed that that female age, BMI, duration of infertility, infertility type, endometrial preparation protocol were not related to the endometrial morphological patterns. Higher serum progesterone level on the day of endometrial transformation (1.506 [95% CI, 0.089\u0026ndash;0.810]; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.020) and lower serum estrogen level on the day of embryo transfer (0.999 [95% CI, 0.999\u0026ndash;1.000]; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.024) were related to the occurrence of triple line endometrium on blastocyst transfer day (Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eUnivariate analysis of endometrial pattern type on blastocyst transfer day in hormone replacement treatment FET cycles\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFactors\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e95% CL\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFemale age\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.972\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.882\u0026ndash;1.070\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.559\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFemale BMI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.039\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.935\u0026ndash;1.154\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.478\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDuration of infertility\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.766\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.586\u0026ndash;1.003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.052\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003eInfertility type\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePrimary infertility\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.105\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSecondary infertility\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.102\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.857\u0026ndash;5.155\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003eEndometrial preparation protocol\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHRT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.843\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGnRHa-HRT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.902\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.324\u0026ndash;2.506\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum estrogen level on the day of endometrial transformation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.000\u0026ndash;1.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.185\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum progesterone level on the day of endometrial transformation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.506\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.043\u0026ndash;2.175\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.029\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum estrogen level on the day of embryo transfer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.999\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.999\u0026minus;1.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.024\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerum progesterone level on the day of embryo transfer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.966\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.924\u0026ndash;1.010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.132\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eAppropriate clinical interventions can optimize endometrial receptivity, achieving an ideal conception state and a successful pregnancy outcome. Endometrial receptivity evaluation involves various methods, including endometrial biopsy, magnetic resonance imaging (MRI), and ultrasound. An endometrial biopsy permits examination of the endometrium at the histological level [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], yet it is an invasive technique with a notable incidence of complications, leading to limited acceptance in clinical practice. MRI offers advantages in delineating endometrial thickness and its relation to the myometrium [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]; however, this method is costly and time-intensive. Ultrasound, prevalent in clinical practice due to its convenience, non-invasiveness, and affordability, is frequently utilized. Research indicates that endometrial thickness might serve as a proxy for endometrial receptivity [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Nevertheless, the utility of the endometrial echo pattern remains a topic of debate as a predictor for endometrial receptivity.\u003c/p\u003e \u003cp\u003eEndometrial echo patterns are identified by comparing the echogenicity of the endometrium with that of the myometrium and by noting a central echogenic line within the endometrium [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. The echo pattern serves as an ultrasonic index reflecting endometrial proliferation and/or stromal decidualization. In 2019, Laurentiu Craciunas et al. conducted systematic meta-analyses to evaluate the evidence from observational studies regarding the use of endometrial receptivity markers as prognostic factors for pregnancy outcomes[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The study concluded that triple line patterns, assessed on the day of hCG injection in IUI, were linked to higher clinical pregnancy rates. However, the endometrial echo pattern on the hCG injection day/embryo transfer day in women undergoing IVF with fresh embryo transfer, or on the day of progesterone supplementation in FET, showed no significant impact on clinical outcomes. However, this conclusion was analyzed from studies with various ovarian stimulation protocols, different embryos transfer numbers and strategies [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRegarding whether the morphology of the endometrium on embryo transfer day (middle luteal phase) impacts clinical outcomes, we posit that the fresh embryo transfer cycle is not an ideal subject of study. The endometrium, a dynamic tissue, undergoes complex physiological changes in response to ovarian steroid hormones [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Various ovulation-inducing treatments lead to significant hormonal fluctuations, which may influence endometrial morphology, complicating classification and discussion. In this study, we analyze HRT cycles with or without GnRHa treatment to eliminate the effects of exogenous or endogenous gonadotrophins. Between 2020 and 2021, HRT and GnRHa-HRT were our primary endometrial preparation protocols, with clinicians not selectively assigning these two protocols to patients. Moreover, our study excluded patients with moderate or severe endometriosis or adenomyosis. The proportion of these 2 protocols in the 4 types of the endometrium were similar (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e1\u003c/span\u003e, \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e2\u003c/span\u003e), and did not affect the live birth rate (Supplementary Table\u0026nbsp;1).\u003c/p\u003e \u003cp\u003eIn cleavage stage embryo FET cycles, the embryo implantation rate, clinical pregnancy rate, early miscarriage rate, and live birth rate were similar in 4 groups and showed no association with endometrial morphology. Regarding the blastocyst cycles, a significant decrease in the live birth rate was observed in the Pattern A group (19.05%), compared with Pattern B (51.67%), Pattern B-C (50.00%), and Pattern C (43.01%) (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.023). Univariate analysis indicated that a triple line endometrium on the embryo transfer day was associated with a higher first trimester abortion rate and a lower live birth rate. Within the 10 clinically pregnant cases in the Pattern A group, 6 women did not achieve a live birth. 4 women experienced first trimester abortions, with 3 undergoing villus tissue analysis, all yielding euploid results. 1 woman had an ectopic pregnancy, marking her second ectopic pregnancy post-embryo transfer. Another woman underwent induced labor due to abnormal fetal development. Through the analysis of the total data and individual abnormal pregnancy cases, we conclude that a trilaminar endometrium on the day of blastocyst transfer is associated with early pregnancy loss. This may be attributed to inadequate decidualization, resulting in trophoblast cell failure to continue invasion and development.\u003c/p\u003e \u003cp\u003eWithin hormone replacement transplantation cycles, estrogen and progesterone are sequentially administered to synchronize embryo transfer with the endometrial window of implantation [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. In cleavage stage embryo FET cycles, serum estrogen and progesterone levels on both the endometrial transformation day and embryo transfer day were similar across the four endometrial morphological types. In blastocyst transfer cycles, serum estrogen levels on endometrial transformation day in the Pattern C group were higher than those in the other three groups. Univariate analysis indicated that higher serum progesterone levels on the day of endometrial transformation and lower serum estrogen levels on the day of embryo transfer were associated with the occurrence of a triple line endometrium on the day of blastocyst transfer. Progesterone is crucial for the transformation of endometrial cells. However, in this context, it seems challenging to clarify the significance of the minute progesterone changes at the molecular/clinical level in terms of endometrial morphology transformation. We posit that estrogen plays a significant role in the transformation of the endometrium.\u003c/p\u003e \u003cp\u003eThe purpose of estrogen priming and the achievement of endometrial proliferation is to induce progesterone receptors, which enable subsequent progesterone stimulation to promote endometrial receptivity. Estrogenic stimulation may significantly affect the subsequent luteal phase, and the luteal progression of the endometrium depends not only on the duration and intensity of progesterone stimulation but also on prior estrogen priming. From 2020 to the present, we have collected two samples from the fifth day post-ovulation, where ultrasound indicated an endometrium of Pattern A. We conducted ER and PR testing on these two samples alongside other Pattern C endometrial samples (Supplementary Fig.\u0026nbsp;2). Due to the limited number of samples, quantitative analysis was not feasible; however, we observed an intriguing case where ERa predominantly expressed in the cytoplasm, rather than in the nucleus. These findings suggest that the morphologically untransformed endometrium of mid-luteal phase may be closely related to aberrant estrogen pathway.\u003c/p\u003e \u003cp\u003eWe also notice the endometrial compaction, which refers to the decrease in endometrial thickness on the day of embryo transfer compared to the starting day of progesterone administration [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. With the endometrium transformed from trilinear pattern to homogeneous hyperechogenic style, the endometrial compaction was increased, which was consistent with the viewpoint that endometrial compaction was associated with the sustained pregnancy.\u003c/p\u003e \u003cp\u003eUnlike the measurement of endometrial thickness, the assessment of endometrial echo possesses a degree of subjectivity. In Julian A's 2015 study, within 180 FET cycles, the endometrial types on blastocyst transfer day were classified as 14 type 2 and 166 type 3, with no type 1 endometrium observed. This could be related to medication methods or ethnic demographics, but it is most likely associated with the subjectivity of the ultrasound physicians. Endometrial pattern is the most crucial observational indicator in our article. Each image was evaluated by the same two doctors, ensuring more stable interpretation. However, this also suggests that if we wish to use endometrial echo pattern as a primary clinical judgment criterion, we should establish a more detailed evaluation system. Artificial intelligence and digitalization are areas that need our attention in the future.\u003c/p\u003e \u003cp\u003eA univariate analysis of 540 blastocyst FET cycles was conducted to identify key factors influencing live birth rates (Supplementary Table\u0026nbsp;1). Consistent with previous studies, female age, BMI, and the number and grades of transferred embryos were associated with live birth rates. We also noted that an endometrium without a triple line was a critical factor affecting live birth rates. However, among the 540 blastocyst transfer cycles, only 19 cases exhibited untransformed endometrium, a very low detection rate (3.74%). Therefore, the necessity of incorporating endometrial echo measurement on the day of transfer into routine clinical practice remains to be considered. Nonetheless, it is necessary to consider this parameter as an important evaluation criterion for populations with recurrent pregnancy loss. It is reasonable to cancel the embryo transfer plan when a trilinear pattern endometrium occurs on the day of blastocyst transfer in FET cycles, especially if the embryo is precious or the patient has had an adverse pregnancy history. If patients have previously experienced mid-luteal phase endometrial non-transformation, we can increase the dosage and method of estrogen administration, or switch to alternative endometrial preparation protocols in subsequent treatment cycles.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIn this manuscript, we discussed the endometrial morphology on cleavage-stage and blastocyst in hormone replacement therapy FET cycle. Our retrospective study suggested that a trilinear pattern endometrium on blastocyst transfer was associated with a higher first trimester abortion rate and lower live birth rate. Estrogen and estrogen receptor may play a significant role in the transformation failure of the endometrium. It is reasonable to cancel the embryo transfer plan when a trilinear pattern endometrium occurs on the day of blastocyst transfer in hormone replacement therapy FET cycles, especially if the embryo is precious or the patient has had an adverse pregnancy history.\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 received ethical approval by the Clinical Ethics Review Committee of Nanjing Jinling Hospital. All methods were carried out in accordance with relevant guidelines and regulations. The informed consent was waived by the same ethics committee that approved the study (the ethics committee of Nanjing Jinling Hospital) \u0026nbsp;due to the retrospective nature. The patients underwent endometrial biopsy examination for medical purpose. Informed consent forms were signed by study participants.\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\u003c/p\u003e\n\u003cp\u003eAll data that support the findings of this study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have declared no conflicts of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work is supported by National Natural Science Foundation of China (Grant: 82101757) and Annual Foundation of Nanjing Jinling Hospital (YYQN2021082, 22LCYY-QH5, 22LCYY-QH12). Each of the funding contributed to expenses related to specific procedures carried out in the project.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eXi Cheng designed the study and contributed to writing the article. Bin Yang and Li Wang contributed to clinical operation and data analysis. Jinzhao Ma and Haiyan Fu contributed to data analysis. Xuan Huang, Cheng Zhou and Tang Xu contributed to clinical operation. Kadiliya Jueraitetibaike contributed to the collection of clinical samples. Li Biying contributed to the molecular experiment. Xiting Cai contributed to the the writing the article. Li Chen and Bing Yao contributed to the study design, data interpretation, as well as article revision. All authors have agreed to be listed and have approved the final article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe thank the other members of Dr. Yao\u0026rsquo;s laboratory for their discussion and help.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eCraciunas L, Gallos I, Chu J, Bourne T, Quenby S, Brosens JJ, Coomarasamy A. Conventional and modern markers of endometrial receptivity: a systematic review and meta-analysis. Hum Reprod Update. 2019;25(2):202\u0026ndash;23.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGarratt J, Rahmati M. Assessing the endometrium: An update on current and potential novel biomarkers of receptivity. J Reprod Immunol. 2023;160:104162.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKasius A, Smit JG, Torrance HL, Eijkemans MJC, Mol BW, Opmeer BC, Broekmans FJM. Endometrial thickness and pregnancy rates after IVF: a systematic review and meta-analysis. Hum Reprod Update. 2014;20(4):530\u0026ndash;41.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGao G, Cui X, Li S, Ding P, Zhang S, Zhang Y. Endometrial thickness and IVF cycle outcomes: a meta-analysis. Reprod Biomed Online. 2020;40(1):124\u0026ndash;33.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDickey RP, Olar TT, Curole DN, Taylor SN, Rye PH. Endometrial pattern and thickness associated with pregnancy outcome after assisted reproduction technologies. Hum Reprod. 1992;7(3):418\u0026ndash;21.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\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(1):166\u0026ndash;75.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBarker MA, Boehnlein LM, Kovacs P, Lindheim SR. Follicular and luteal phase endometrial thickness and echogenic pattern and pregnancy outcome in oocyte donation cycles. J Assist Reprod Genet. 2009;26(5):243\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBassil S. Changes in endometrial thickness, width, length and pattern in predicting pregnancy outcome during ovarian stimulation in in vitro fertilization. Ultrasound Obstet Gynecol. 2001;18(3):258\u0026ndash;63.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen S-L, Wu F-R, Luo C, Chen X, Shi X-Y, Zheng H-Y, Ni Y-P. Combined analysis of endometrial thickness and pattern in predicting outcome of in vitro fertilization and embryo transfer: a retrospective cohort study. Reprod Biol Endocrinol. 2010;8:30.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSingh N, Bahadur A, Mittal S, Malhotra N, Bhatt A. Predictive value of endometrial thickness, pattern and sub-endometrial blood flows on the day of hCG by 2D doppler in in-vitro fertilization cycles: A prospective clinical study from a tertiary care unit. J Hum Reprod Sci. 2011;4(1):29\u0026ndash;33.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang W, Zhang T, Li Z, Ren X, Huang B, Zhu G, Jin L. Combined analysis of endometrial thickness and pattern in predicting clinical outcomes of frozen embryo transfer cycles with morphological good-quality blastocyst: A retrospective cohort study. Med (Baltim). 2018;97(2):e9577.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRashidi BH, Sadeghi M, Jafarabadi M, Tehrani Nejad ES. Relationships between pregnancy rates following in vitro fertilization or intracytoplasmic sperm injection and endometrial thickness and pattern. Eur J Obstet Gynecol Reprod Biol. 2005;120(2):179\u0026ndash;84.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAhmadi F, Akhbari F, Zamani M, Ramezanali F, Cheraghi R. Value of Endometrial Echopattern at HCG Administration Day in Predicting IVF Outcome. Arch Iran Med. 2017;20(2):101\u0026ndash;4.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiao S, Wang R, Hu C, Pan W, Pan W, Yu D, Jin L. Analysis of endometrial thickness patterns and pregnancy outcomes considering 12,991 fresh IVF cycles. BMC Med Inf Decis Mak. 2021;21(1):176.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCheck JH, Dietterich C, Lurie D. Non-homogeneous hyperechogenic pattern 3 days after embryo transfer is associated with lower pregnancy rates. Hum Reprod. 2000;15(5):1069\u0026ndash;74.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCheck JH, Dietterich C, Nazari A, Lurie D, Choe JK, Check ML. Non-homogeneous hyperechogenic echo pattern three days after frozen embryo transfer is associated with lower pregnancy rates. Clin Exp Obstet Gynecol. 2005;32(1):15\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCheck JH, Gandica R, Dietterich C, Lurie D. Evaluation of a nonhomogeneous endometrial echo pattern in the midluteal phase as a potential factor associated with unexplained infertility. Fertil Steril. 2003;79(3):590\u0026ndash;3.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMaugey-Laulom B, Commenges-Ducos M, Jullien V, Papaxanthos-Roche A, Scotet V, Commenges D. Endometrial vascularity and ongoing pregnancy after IVF. Eur J Obstet Gynecol Reprod Biol. 2002;104(2):137\u0026ndash;43.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eThe Istanbul consensus workshop on embryo. assessment: proceedings of an expert meeting. Hum Reprod 2011, 26(6):1270\u0026ndash;1283.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGardner DK, Lane M, Stevens J, Schlenker T, Schoolcraft WB. Blastocyst score affects implantation and pregnancy outcome: towards a single blastocyst transfer. Fertil Steril. 2000;73(6):1155\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhao J, Zhang Q, Wang Y, Li Y. Endometrial pattern, thickness and growth in predicting pregnancy outcome following 3319 IVF cycle. Reprod Biomed Online. 2014;29(3):291\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSmith B, Porter R, Ahuja K, Craft I. Ultrasonic assessment of endometrial changes in stimulated cycles in an in vitro fertilization and embryo transfer program. J Vitro Fert Embryo Transf. 1984;1(4):233\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMoustafa S, Young SL. Diagnostic and therapeutic options in recurrent implantation failure. F1000Res 2020, 9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMeylaerts LJ, Wijnen L, Ombelet W, Bazot M, Vandersteen M. Uterine junctional zone thickness in infertile women evaluated by MRI. J Magn Reson Imaging. 2017;45(3):926\u0026ndash;36.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBergin K, Eliner Y, Duvall DW, Roger S, Elguero S, Penzias AS, Sakkas D, Vaughan DA. The use of propensity score matching to assess the benefit of the endometrial receptivity analysis in frozen embryo transfers. Fertil Steril. 2021;116(2):396\u0026ndash;403.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGonen Y, Casper RF. Prediction of implantation by the sonographic appearance of the endometrium during controlled ovarian stimulation for in vitro fertilization (IVF). J Vitro Fert Embryo Transf. 1990;7(3):146\u0026ndash;52.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCheck JH, Lurie D, Dietterich C, Callan C, Baker A. Adverse effect of a homogeneous hyperechogenic endometrial sonographic pattern, despite adequate endometrial thickness on pregnancy rates following in-vitro fertilization. Hum Reprod. 1993;8(8):1293\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSharara FI, Lim J, McClamrock HD. Endometrial pattern on the day of oocyte retrieval is more predictive of implantation success than the pattern or thickness on the day of hCG administration. J Assist Reprod Genet. 1999;16(10):523\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePuerto B, Creus M, Carmona F, Civico S, Vanrell JA, Balasch J. Ultrasonography as a predictor of embryo implantation after in vitro fertilization: a controlled study. Fertil Steril. 2003;79(4):1015\u0026ndash;22.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRuiz-Alonso M, Valbuena D, Gomez C, Cuzzi J, Simon C. Endometrial Receptivity Analysis (ERA): data versus opinions. Hum Reprod Open. 2021;2021(2):hoab011.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOwusu-Akyaw A, Krishnamoorthy K, Goldsmith LT, Morelli SS. The role of mesenchymal-epithelial transition in endometrial function. Hum Reprod Update. 2019;25(1):114\u0026ndash;33.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZilberberg E, Smith R, Nayot D, Haas J, Meriano J, Barzilay E, Casper RF. Endometrial compaction before frozen euploid embryo transfer improves ongoing pregnancy rates. Fertil Steril. 2020;113(5):990\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi Q, Liu A, Shen H, Zhang X. Endometrial compaction after human chorionic gonadotrophin administration reduces ectopic pregnancy rate following fresh embryo transfer in vitro fertilization/intracytoplasmic sperm injection cycles in patients with non-thin endometrium: a retrospective cohort study. Reprod Biol Endocrinol. 2022;20(1):151.\u003c/span\u003e\u003c/li\u003e\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":"bmc-pregnancy-and-childbirth","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"prch","sideBox":"Learn more about [BMC Pregnancy and Childbirth](http://bmcpregnancychildbirth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/prch/default.aspx","title":"BMC Pregnancy and Childbirth","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"FET, Endometrial echo patterns, First trimester abortion rate, Live birth rate","lastPublishedDoi":"10.21203/rs.3.rs-3955580/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3955580/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground: \u003c/strong\u003eEcho pattern is the ultrasonic index reflecting endometrial proliferation and/or stromal decidualization. However, consensus of endometrial echo pattern and IVF pregnant outcomes is lacking in clinical application.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e: The retrospective cohort study analyzed the data from the electronic records of women who underwent frozen embryo transfer (FET) with hormone replacement treatment (not only one cycle per patient) between July 2020 to August 2021 at Reproduction Medicine Center of Jinling Hospital of Medical College of Nanjing University. A total of 159 cleavage stage embryo transfer cycles and 540 blastocyst transfer cycles were analyzed in this study. Transvaginal ultrasound scans were performed on the embryo transfer day. The endometrial echo pattern was classified into four types: A, B, B-C and C. Pattern A was defined as trilinear type, Pattern B, B-C and C were defined as not trilinear type. All scans were conducted by experienced clinicians, and the images were reviewed by the same two physicians. The outcomes measured included embryo implantation rate, clinical pregnancy rate, first trimester abortion rate, and live birth rate.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e The embryo implantation rate (\u003cem\u003ep\u003c/em\u003e=0.066), clinical pregnancy rate (\u003cem\u003ep\u003c/em\u003e=0.140), early abortion rate (\u003cem\u003ep\u003c/em\u003e=0.515) and live birth rate (\u003cem\u003ep\u003c/em\u003e=0.578) were similar between the 4 type of endometrial pattern groups in cleavage-stage embryo FET cycles. In blastocyst cycles, the implantation rate (\u003cem\u003ep\u003c/em\u003e=0.201) and clinical pregnancy rate (\u003cem\u003ep\u003c/em\u003e=0.555) did not differ between the four endometrial patterns. Patients with a Pattern A endometrium on blastocyst transfer day experienced a decreased live birth rate (19.05%) compared with Pattern B, Pattern B-C and Pattern C (\u003cem\u003ep\u003c/em\u003e=0.006. \u003cem\u003ep\u003c/em\u003e=0.008, \u003cem\u003ep\u003c/em\u003e=0.031 for Pattern A \u003cem\u003evs\u003c/em\u003e. Pattern B, Pattern A \u003cem\u003evs\u003c/em\u003e. Pattern B-C, Pattern A \u003cem\u003evs\u003c/em\u003e. Pattern C). The first trimester abortion rate of Pattern A is up to 40.00%, although there was no statistical difference (\u003cem\u003ep\u003c/em\u003e=0.118). In the cycles of not trilinear type group, the early miscarriage rate (0.248 [95% CI, 0.067–0.914]; p=0.036) was lower and the live birth rate (0.269 [95% CI, 0.089–0.810]; p=0.020) was higher than trilinear type group.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions: \u003c/strong\u003eOur retrospective study suggests that a trilinear pattern endometrium on blastocyst transfer was associated with a higher first trimester abortion rate and lower live birth rate.\u003c/p\u003e","manuscriptTitle":"Endometrial echo patterns of embryo transfer day affect pregnancy outcomes in frozen embryo transfer cycles: a retrospective clinical study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-02-23 19:11:33","doi":"10.21203/rs.3.rs-3955580/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-08-07T16:04:27+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-08-02T06:51:34+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-07-30T16:42:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"179289739747579113005238164685814522458","date":"2024-07-29T08:59:03+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"5207058032088068791431450136806234521","date":"2024-07-19T18:55:30+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-05-23T05:13:01+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-05-17T08:27:10+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2024-02-22T07:39:54+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-02-22T07:23:40+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Pregnancy and Childbirth","date":"2024-02-14T08:18:44+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-pregnancy-and-childbirth","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"prch","sideBox":"Learn more about [BMC Pregnancy and Childbirth](http://bmcpregnancychildbirth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/prch/default.aspx","title":"BMC Pregnancy and Childbirth","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"87956d9b-997e-4b19-9346-522919c173bd","owner":[],"postedDate":"February 23rd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-04-14T16:12:37+00:00","versionOfRecord":{"articleIdentity":"rs-3955580","link":"https://doi.org/10.1186/s12884-025-07501-7","journal":{"identity":"bmc-pregnancy-and-childbirth","isVorOnly":false,"title":"BMC Pregnancy and Childbirth"},"publishedOn":"2025-04-10 16:04:57","publishedOnDateReadable":"April 10th, 2025"},"versionCreatedAt":"2024-02-23 19:11:33","video":"","vorDoi":"10.1186/s12884-025-07501-7","vorDoiUrl":"https://doi.org/10.1186/s12884-025-07501-7","workflowStages":[]},"version":"v1","identity":"rs-3955580","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3955580","identity":"rs-3955580","version":["v1"]},"buildId":"omnImTCwR2MFx8CMYfrG7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}