Combined analysis of estradiol and β-hCG to predict the early pregnancy outcome of FET: a retrospective study

Combined analysis of estradiol and β-hCG to predict the early pregnancy outcome of FET: a retrospective study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Combined analysis of estradiol and β-hCG to predict the early pregnancy outcome of FET: a retrospective study Man Wu, Xiao Xiao, Chen Wang, Min Zhao, Fang Xiong, Xin Jin, Xiaomin Zheng This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4078359/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 7 You are reading this latest preprint version Abstract Background How to accurately predicting the pregnancy outcomes of an IVF cycle are particularly important. Although a lot of work was conducted to predict pregnancy outcomes by assaying serum β-hCG levels after embryo transfer, rare study has focused on the prediction of serum E 2 level after transfer. This study sought to analyze the predictive effect of serum E 2 combined with β-hCG on early reproductive outcomes 12 days after embryo transfer. Methods A total of 1521 patients with β-hCG positive values on day 12 after frozen-warmed embryo transfer (FET) in natural endometrial preparation cycles (NCs) were collected in affiliated Women’s Hospital of Jiangnan University. Logistic regression analysis was constructed to establish the clinical pregnancy prediction model, and the cutoff value, optimal sensitivity and specificity were calculated by Receiver operating characteristic (ROC). Results Levels of serum E 2 and β-hCG on the 12th day after FET with NCs were higher in clinical pregnancy group (CP Group) compared with biochemical pregnancy group (BP Group) (P < 0.001). Besides, the cutoff values for E 2 and β-hCG on the 12th day after FET with NCs in cleavage group (CE Group) were 129.25 pg/mL and 156.60 mIU/mL respectively, with area under the ROC curve (AUC) of 0.801 and 0.941 respectively. For blastocyst group (B Group), the cutoff values for E 2 and β-hCG were 174.45 pg/mL and 217.70 mIU/mL, with AUCs of 0.762 and 0.924 respectively. The logistic regression analysis revealed that serum E 2 day 12 and β-hCG day 12 were significantly associated with clinical pregnancy. Conclusions Serum E 2 is significantly different in CP Group compared with BP Group in FET with NCs. Earlier E 2 combined with β-HCG can be used as a predictor of early pregnant state. Estradiol β-hCG cutoff value clinical pregnancy biochemical pregnancy frozen-warmed embryo transfer Figures Figure 1 Figure 2 Background Infertility affects one in six people globally[ 1 ], which affects approximately 13 hundred million people globally and 1.3 hundred million people in China. In vitro fertilization-embryo transfer (IVF-ET) is currently the most commonly used assisted reproductive techniques (ART). Although IVF success rates are substantially higher today than a few years ago as remarkable advances have been made in in recent years, it’s still a challenging issue in clinical IVF practice, due to the variable effects factors such as man’s sperm condition, maternal age, cause of infertility, embryo status, endometrial receptivity, reproductive history, lifestyle factors and so on[ 2 ]. Then how to accurately predicting the outcome of an IVF cycle has emerged as a particularly important clinical problem that needs to be solved urgently. The clinicians usually use the combination of β-human chorionic gonadotropin (β-hCG) and progesterone (P) to predict the prognosis of pregnancy outcomes in women who conceived naturally or via ART[ 3 , 4 ]. However, conflicts about how to predict adverse pregnancy outcome, such as biochemical pregnancy so that to promote a safe transition of clinical pregnancy and avoid biochemical pregnancy has been challenged for many years. The role of estradiol (E 2 ) is well documented in IVF cycles, particularly in fertilization and implantation. Many research in hints that successful IVF and a healthy pregnancy is associated with the levels of estrogen. Currently, a number of studies suggested that levels of hormones such as E 2 may play a role in predicting successful pregnancy in IVF cycles[ 5 , 6 ], but these results are controversial[ 7 , 8 ]. What’s more, most previous studies paid attention to the association of clinical outcomes with E 2 on the day of β-hCG administration, or E 2 related with fresh embryo transplantation. However, rare study investigated earlier serum E 2 levels on day 12 after FET with NCs and lately clinical pregnancy outcomes. As we know endometrial preparation protocol can mainly be divided into hormonal replacement treatment cycles (HRTs), ovarian stimulation cycle(GnRH-a) and NCs, which is an important factor affecting the pregnancy rate of FET[ 9 ], and so we wondered if serum E 2 levels are associated with successful clinical pregnancy of FET. To rule out the effects of hormone supplementation, we just focused on infertile women undergoing FET with NCs group. Therefore, we undertook this retrospective study and evaluated the predictive value for earlier serum E 2 and β-hCG on the 12th day after FET with NCs. In this research, the association between E 2 level and clinical outcomes in infertility women underwent FET with NCs will be investigated, and we also hope to establish E 2 cutoff values for the prediction of clinical pregnancy earlier on day 12 after FET. So that the doctors could evaluated the lately outcomes in advance and could have more accurent index, in order to provide patients with necessary individualized treatments before the real gestational sac can be documented by ultrasound 28–35 days after FET[ 10 ]. Besides that, we can reduce the number of patient visits and serum hormone tests, which will decrease psychological and economic stress of patients. Materials and methods All procedures in this study were approved by the Ethics Committee of Affiliated Women’s Hospital of Jiangnan University(2023-06-1213-65). Cohort selection In this retrospective study, infertile women ongoing FET with NCs were collected according to the electronic based medical records of patients from 2012 to 2022. Clinical characteristics included maternal age at diagnosis, nationality, the years of infertility, body mass index (BMI), basal estradiol (bE 2 ), basal follicle-stimulating hormone (bFSH) and basal luteinizing hormone (bLH), anti-Müllerian hormone (AMH), basal prolactin (bPRL), β-hCG and so on. Weight and height at time of diagnosis were measured by BMI calculated and classified according to the ethnicity-specific WHO classification for Asian/Indian women: underweight (under 18.4 kg/m 2 ), normal weight (18.5-22.99 kg/m 2 ), overweight (23–27.49 kg/m 2 ), and obese (over 27.50 kg/m 2 )[ 11 ]. The study included the patients with age of no more than 35 years old and without major system disease. We excluded the patients with uterine malformation, uterine fibroids or adenomyosis, severely damaged endometrium and chromosomal abnormalities of either part of the couple. Patients with incomplete basic endocrine parameters and untimely β-hCG and E 2 data were also excluded. The patients whose endometrium was less than 8 mm were not included. Finally, 1521 cycles with β-hCG positive were collected. The data was divided into two groups which are CE Group (n = 595) and B Group (n = 926). We then subdivided CE Group to clinical pregnancy group (CE-CP Group, with gestational sac) and biochemical pregnancy group (CE-BP Group, without gestational sac) according to the β-hCG positive (β-hCG ≥ 5 mIU/mL) data 12 day after FET[ 12 ]. B Group was samely divided into blastocyst-clinical pregnancy group (B-CP Group) and blastocyst-biochemical pregnancy group (B-BP Group). Treatment protocols and outcome variables assessed The patients who had a history of spontaneous ovulation were recruited and they were carried out FET with NCs. The FET was performed until the endometrium was not less than 8 mm. The number of embryos to transfer (one or two) were determined according to embryo quality, patient age, uterine condition and so on. Pregnancy outcomes were as follows: biochemical pregnancy, clinical pregnancy, ongoing pregnancy, and live birth[ 13 ]. Biochemical pregnancy was defined by serum β-hCG positive test[ 14 ], and that fails to progress to the point of ultrasound confirmation of gestational sac 28–35 days after embryo transfer. While clinical pregnancy was defined by presenting gestational sac using ultrasound scan after embryo transfer. So, in other words, biochemical pregnancy was the pregnancy which doesn’t end up with clinical pregnancy. On the morning of cycle day 12 after embryo transfer, blood was drawn and serum E 2 and β-hCG were measured. Our choice of post-ET day 12 is based on the fact that most of our patients had their first serum samples collected on this day. If the serum β-hCG value was ≥ 5 mIU/mL, it was considered as biochemical pregnancy[ 15 ], and those at least one gestational sac can be documented by ultrasound 28–35 days after transfer were count as clinical pregnancy. Statistical analysis IBM SPSS Statistics for Windows Version 27.0 (Armonk, NY: IBM Corp) software was used to analyze all the data. And the continuous data were calculated as mean and standard deviation (̄x ± s), the difference was assessed using T-test. Spearman’s rank correlation ( r s ) was used to examine the correlation between day 12 E 2 and β-hCG levels. ROC curve analysis was applied to assess the predictive accuracy of day 12 E 2 and β-hCG levels. ROC curves were generated by joining points defined by sensitivity (true-positive fraction) and corresponding 1-specificity (false-positive fraction) values. The percentage for AUC and 95% confidence intervals were reported for each ROC curve analysis. AUC measures the diagnostic accuracy of the test, with a greater area corresponding to a greater ability to discriminate between patients with clinical pregnancy or not. AUC < 0.5 indicated no predictive value, 0.5 ≤ AUC < 0.7 indicated a low predictive value, 0.7 ≤ AUC < 0.9 indicated a moderate prediction value and 0.9 ≤ AUC < 1 indicated a high predictive value. Univariate logistic regression analyses were used to study the association between variables (day 12 E 2 levels and day 12 β-hCG concentration) and pregnancy outcome. Statistical significance was set at a two-sided P < 0.05. Results General characteristics of the included patients The general characteristics of the included patients are presented in Table 1 . There were 1521 cycles of β-hCG positive which consists of 595 cycles with CE Group and 926 cycles with B Group. General characteristics in age, duration of infertility, BMI, AMH, bFSH, bE 2 , bPRL and bLH were compared between CE-CP Group, CE-BP Group and B-CP Group, B-BP Group respectively. Significant differences were observed in Table 1 . Groups are similar in age, duration of infertility, BMI, AMH, bFSH, bE 2 , bPRL and bLH. Table 1 General characteristics of the included patients Characteristic Group (n = 1521) CE Group (n = 595) B Group (n = 926) CE-CP Group (n = 501) CE-BP Group (n = 94) t/χ2 P value B-CP Group (n = 759) B-BP Group (n = 167) t/χ2 P value Age (̄x ± s) 29.90 ± 3.19 30.33 ± 3.02 1.203 0.229 30.27 ± 2.84 30.71 ± 3.07 1.779 0.076 Duration of infertility (years, ̄x ± s) 3.83 ± 2.55 4.38 ± 2.71 1.806 0.073 4.32 ± 2.51 4.38 ± 2.76 0.264 0.792 BMI (̄x ± s, kg/m 2 ) 21.63 ± 2.73 21.07 ± 2.50 -1.857 0.064 21.71 ± 2.91 21.46 ± 2.72 -1.007 0.314 bFSH (mIU/mL) 7.45 ± 2.06 7.01 ± 2.03 -1.918 0.056 7.22 ± 2.26 7.29 ± 2.12 0.352 0.725 bE 2 (pg/mL) 36.33 ± 26.86 41.18 ± 17.81 1.684 0.093 38.20 ± 18.10 40.31 ± 21.19 1.320 0.187 bPRL (ng/mL) 15.32 ± 7.68 15.29 ± 7.33 -0.036 0.971 15.11 ± 6.26 14.93 ± 6.85 -0.331 0.740 bLH (mIU/mL) 4.82 ± 3.70 4.60 ± 1.85 -0.552 0.581 5.43 ± 4.50 5.13 ± 3.39 -0.812 0.417 AMH (ng/mL) 4.08 ± 2.58 3.68 ± 2.51 -1.387 0.166 4.33 ± 2.71 4.11 ± 2.64 -0.950 0.342 BMI = body mass index; AMH = anti-Müllerian hormone; bfsh = basal follicle-stimulating hormone; bE 2 = basal estradiol; bPRL = basal prolactin; bLH = basal luteinizing hormone; B-CP = blastocyst-clinical pregnancy; B-BP = blastocyst-biochemical pregnancy; CE-CP = cleavage embryo-clinical pregnancy; CE-BP = cleavage embryo-biochemical pregnancy. Hormone profile of serum E 2 and β-hCG were significantly higher in clinical pregnancy The serum E 2 levels were compared among all groups on the 12th day after FET with NCs. We found significantly higher serum E 2 levels in CE-CP Group compared with CE-BP Group (212.04 ± 151.27 vs 121.18 ± 43.18 pg/mL, P < 0.001). Furthermore, the difference between B-CP Group B-BP Group was also significant (215.06 ± 96.80 vs 135.87 ± 55.20, P < 0.001). In this analysis, there was also significantly difference in β-hCG level on day 12 after FET with NCs between CE-CP Group and CE-BP Group (β-hCG, 474.73 ± 351.88 vs 69.18 ± 43.41 mIU/mL, P < 0.001). The same was true in B Group for β-hCG level (832.88 ± 694.36 vs 107.49 ± 88.44 mIU/mL, P < 0.001) on day 12 after FET with NCs. The average number of embryos transferred in CE-CP Group, CE-BP Group, B-CP Group and B-BP Group were 1.91, 1.89, 1.53 and 1.46 respectively, there were no significant difference between CE-CP Group and CE-BP Group (P > 0.05), and the same to B-CP Group and B-BP Group (P > 0.05). Between CE-CP Group and CE-BP Group, the difference was not significant in terms of number of top-quality embryos transferred (1.60 ± 0.69 vs 1.53 ± 0.74, P > 0.05). The difference was the same in B-CP Group and B-BP Group (1.00 ± 0.68 vs 0.89 ± 0.66, P > 0.05) (Table 2 ). As to the endometrial thickness for transferring embryo, the mean was similar in patients of CE Group (10.17 ± 1.71 vs 10.04 ± 1.74, P > 0.05) and B Group (10.25 ± 1.68 vs 10.40 ± 1.81, P > 0.05). Table 2 Cycle parameters and day 12 serum E 2 and β-hCG levels after FET with NCs Cycle parameters Group (n = 1521) CE Group (n = 595) B Group (n = 926) CE-CP Group (n = 501) CE-BP Group (n = 94) t/χ2 P value B-CP Group (n = 759) B-BP Group (n = 167) t/χ2 P value number of embryos transferred 1.91 ± 0.52 1.89 ± 0.50 -0.249 0.803 1.53 ± 0.50 1.46 ± 0.50 -1.730 0.084 number of top-quality embryos transferred 1.60 ± 0.69 1.53 ± 0.74 -0.854 0.393 1.00 ± 0.68 0.89 ± 0.66 -1.922 0.055 Endometrial thickness (mm) 10.17 ± 1.71 10.04 ± 1.74 -0.683 0.495 10.25 ± 1.68 10.40 ± 1.81 1.408 0.295 Day 12 E 2 levels after FET (pg/mL) 212.04 ± 151.27 112.18 ± 43.18 -12.34 <0.001 215.06 ± 96.80 135.87 ± 55.20 -14.317 <0.001 Day 12 β-hCG levels after FET (mIU/mL) 474.73 ± 351.88 69.18 ± 43.41 -24.81 <0.001 832.88 ± 694.36 107.49 ± 88.44 -27.78 <0.001 B-CP = blastocyst-clinical pregnancy; B-BP = blastocyst-biochemical pregnancy; CE-CP = cleavage embryo-clinical pregnancy; CE-BP = cleavage embryo-biochemical pregnancy; FET = frozen-warmed embryo transfer; NCs = natural endometrial preparation cycles; E 2 = estradiol AUC analysis hormone profile of serum E 2 and β-hCG levels in predicting clinical pregnancy after FET with NCs The ability of serum E 2 and β-hCG levels to predicting transplant outcomes was evaluated by the AUC analysis (Fig. 2). For CE Group, serum E 2 levels were associated with a moderate probability of clinical pregnancy (AUC = 0.801, sensitivity = 74.45%, specificity = 71.28%, cutoff value = 129.25 mIU/mL). In terms of β-hCG, the cutoff value was 156.60 mIU/mL to predict clinical pregnancy, with sensitivity of 84.20%, specificity of 95.74% and high predictive value for clinical pregnancy. For B Group, the cutoff values for E 2 and β-hCG were 174.45 pg/mL and 217.70 mIU/mL, separately to predict the probability of clinical pregnancy, with AUCs of 0.762 and 0.924 respectively, with sensitivity of 63.77% and 81.56% respectively, with specificity of 77.84% and 94.01% respectively. The differences were all significant. Significantly relations between day 12 E 2 and β-hCG levels Serum day 12 E 2 and β-hCG levels correlated significantly in CE Group ( r s =0.117; P = 0.004) and B Group ( r s =0.170; P < 0.001). Association between variables and clinical outcome by logistic analyses Logistic regression analysis showed day 12 serum levels of E 2 and β-hCG concentrations were the significant predictors of clinical pregnancy (Table 3 ). The analysis revealed that serum E 2 day 12 and β-hCG day 12 were significantly associated with clinical pregnancy in CE Group [E 2 day 12 : odds ratio (OR) of 0.978 (95% CI 0.972–0.984); β-hCG day 12 : OR of 0.979 (95% CI 0.973–0.984)] and B Group [E 2 day 12 : OR of 0.986 (95% CI 0.983–0.989); β-hCG day 12 : OR of 0.988 (95% CI 0.986–0.991)]. Table 3 Predictive accuracy of serum day 12 E 2 and β-hCG concentrations Odds ratio (95% CI) p AUC (95%CI) Optimal cutoffpoint Sensitivity Specificity Prediction of clinical pregnancy of cleavage embryos Day 12 E 2 levels (pg/mL) 0.978 (0.972–0.984) P < 0.001 0.801 (0.756–0.846) 129.25 mIU/ml 74.45% 71.28% Day 12 β-hCG levels (mIU/mL) 0.979 (0.973–0.984) P < 0.001 0.941 (0.923–0.959) 156.60 mIU/ml 84.20% 95.74% Prediction of clinical pregnancy of blastocyst embroys Day 12 E 2 levels (pg/mL) 0.986 (0.983–0.989) P < 0.001 0.762 (0.726–0.799) 174.45 mIU/ml 63.77% 77.84% Day 12 β-hCG levels (mIU/mL) 0.988 (0.986–0.991) P < 0.001 0.924 (0.907–0.941) 217.70 mIU/ml 81.56% 94.01% CI = confidence interval Discussion IVF overcomes many causes of infertility over the past decade, but the embryo implantation rate remained relatively low over the past decade[ 16 , 17 ]. And patients with low β-hCG values are often very anxious about their pregnancy outcomes. Then the problem has highlighted, how to accurately predicting the pregnancy outcomes of an IVF cycle are particularly important. So we calculated this study to analyze the roles of day 12 serum E 2 and β-hCG in predicting the early reproductive outcomes and to determine the cutoff values in women undergoing FET with NCs. Hormones involved in regulating uterine changes during placentation As we know multiple steroid hormones and growth factors are involved in regulating uterine changes during placentation[ 18 ]. In which β-hCG was considered as the most important. Previous research revealed that serum levels of β-hCG plays a key role in predicting clinical pregnancy in IVF cycles[ 19 , 20 ]. Undoubtedly, β-hCG is essential for the maintained of pregnancy. Moreover, β-hCG is also involved in the regulation of progesterone expression via the ERK1/2 pathway[ 21 ], and promote cytotrophoblast differentiation and endometrial stromal cell decidualization[ 22 , 23 ]. P transforms the E 2 -prepared endometrium into a secretory tissue and creates a hospitable environment for embryo attachment[ 24 ]. Estrogens are essential hormones in uterine physiology[ 25 ]. At the very early stage of human pregnancy, E 2 is mainly produced by corpus luteum of ovaries until the ovary to placental shift occurs[ 26 ], which are needed for successful embryo implantation[ 27 ]. Current clinical pregnancy prediction methods and defaults The combination of β-hCG and P has been used to predict the pregnancy outcomes in women who underwent ART or conceived naturally[ 3 , 4 ]. Normally, serum β-hCG and P are lower in nonpregnant women, and their levels could rise significantly after pregnancy. Yuan, et al.[ 28 ] found that β-hCG levels were associated with the number of embryos. But other studies[ 29 , 30 ] reclaimed that the serum levels of β-hCG was no difference in women transferred with one embryo compared with two embryos. Zhang, et al.[ 29 ] proposed that the difference was consistent as to the number of transferring high quality. Wang Z, et al.[ 20 ] indicated that elevated serum β-HCG levels resulted in decreased biochemical pregnancy rates, increased multiple rates, and decreased ongoing and ectopic pregnancy rates, while it has no meaningful clinical utility to predict adverse pregnancy outcomes. The role of E 2 is well documented in IVF cycles, in particular in fertilization and implantation. Study using mice models showed the variations of E 2 levels plays an important role in determining the window of opportunity for an embryo to attach itself to the uterine wall and begin development[ 27 ]. Clinical outcomes in infertility women underwent FET with NCs. Uterine decidualization supports embryo implantation and placentation as well as subsequent events, which maintain a successful pregnancy together[ 31 ]. Latest research indicated that endometrial receptivity but not embryo quality is a key factor restricting successful pregnancy after FET. HRTs, GnRH-a or NCs which were used for the endometrial preparation[ 32 ] can be observed as an important factor affecting the pregnancy rate of FET. To rule out the effect of hormone supplementation, we focus on infertility women underwent FET with NCs, and hope to evaluated the association between E 2 level and clinical outcomes in infertility women underwent FET with NCs. Hormone profile of E 2 combined with β-hCG on day 12 after FET with NCs to evaluated pregnancy outcomes Previous studies have revealed that the levels of E 2 in luteal phase are associated with the outcome of IVF and suggested that E 2 levels of corpus luteum may be able to be a potential predictor of ongoing pregnancy post-clinical pregnancy[ 6 , 33 , 34 ]. However, some results are controversial[ 8 ]. Goldman RH et al.[ 7 ] found high levels of serum E 2 on the day of progesterone start may be detrimental to implantation, pregnancy, and live birth following FET. Supraphysiologic serum E 2 levels may negatively impact the likelihood of conception and live birth following IVF. A study reported that higher ratio of E 2 and P on the day of embryo transfer has better pregnancy outcome[ 35 ]. In addition, a most recent study reported that lower E 2 levels in cycle days 28 (22 days after fresh embryo transfer) were associated with pooper pregnancy outcome[ 24 ]. There are also some other related researches which mostly paid attention to the association of clinical outcomes with E 2 on the day of β-hCG administration, or E 2 related with fresh embryo transplantation. Although previous research has established that E 2 and P regulate events leading to implantation, relatively little is known about their relative proportion in maternal serum during the early luteal phase. Until now rare studies investigating the association between the pregnancy outcomes and E 2 on day 12 after FET with NCs. In this retrospective cohort study, we investigated the association between E 2 level and clinical outcomes in infertility women underwent FET with NCs, and E 2 cutoff values had been established, which it can combined with β-hCG level on day 12 after FET with NCs to evaluated both positive and adverse pregnancy outcomes. We found that E 2 levels were significantly higher in the clinical pregnancy group than in the biochemical pregnancy group on the 12th day after FET with NCs, suggesting a strong link between E 2 levels and clinical outcomes. Low levels of E 2 may affect the development and maturation of endometrial glands and ultimately reduce the clinical pregnancy rate. However, the thresholds at which elevated E 2 levels may adversely affect endometrial receptivity have not yet been elucidated. With the serum E 2 level combined with β-hCG on day 12 after FET, the doctors could evaluate the outcomes in advance and could have more accurent index to evaluated both positive and adverse pregnancy outcomes, and then to provide patients with necessary individualized treatments. In addition, we can reduce the number of patient visits and serum hormone tests, which will decrease psychological and economic stress of patients. Conclusion ART is an ideal solution for many couples suffering from infertility, and nowadays how to improve the embryo implantation rate has become an appealing topic. The treatment of progesterone has been widely used in clinical treatment to improve the pregnancy outcomes in patients in early pregnancy, and the serum β-hCG values 14 days after embryo transplantation are widely used to predict pregnancy outcomes, while the detection and supplement of estrogen seems to be ignored, here we mainly focus with hormone profile of E 2 combined with β-hCG on day 12 after FET with NCs to evaluate both positive and negative pregnancy outcomes. Our evidence clearly indicates that, biochemical pregnancy is significantly different in serum E 2 level compared with clinical pregnancy after FET with NCs and the E 2 cutoff values for predicting clinical pregnancy after FET with NCs were proposed. Our results from the retrospective cohort study indicates that the cutoff values of E 2 with acceptable sensitivity and specificity for predicting clinical pregnancy were 129.25 pg/mL for CE Group and 174.45 pg/mL for B Group. Earlier E 2 combined with β-hCG on day 12 after FET can be used as a predictor to evaluated both positive and adverse pregnancy outcomes after FET with NCs. In conclusion, these findings demonstrate that besides day 12 serum β-hCG concentrations, serum day 12 E 2 levels can also predict clinical pregnancy after FET with NCs. What’s more, the value of serum day 12 E 2 and β-hCG levels for predicting clinical pregnancies were equally important. There is a significant correlation between the day 12 E 2 and β-hCG levels. Therefore, the inclusion of day 12 E 2 levels into the panel for routine follow up of FET with NCs pregnancies is justified by our study. Abbreviations FET: frozen-warmed embryo transfer; NCs: in natural endometrial preparation cycles; CP Group: clinical pregnancy group; BP Group: biochemical pregnancy group; CE Group: cleavage group; B Group: blastocyst group; IVF-ET: in vitro fertilization-embryo transfer; ART: assisted reproductive techniques; E 2 : estradiol; β-hCG: β-human chorionic gonadotropin; P: progesterone; HRTs: hormonal replacement treatment cycles; GnRH-a: ovarian stimulation cycle; ROC: receiver operating characteristic; AUC: area under the ROC curve; CI: confidence interval. Declarations Author contributions Zheng Xiaomin and Zhao Min together conceived and designed the experiments. Wu Man, Xiao Xiao collected the clinical data and performed most of the analysis. Wang Chen analyzed part of the data. Xin Jin contributed the tools for analysis. Wu Man and Zheng Xiaomin drafted the paper. Xiong Fang participated in part of the paper writing and revised. All authors have read and approved the final manuscript. Funding statement The study was funded by Jiangsu Province Innovation and Entrepreneurship Program (JSSCRC2021569), Jiangsu Province Medical Distinguished Expert, and Wuxi "Taihu Talent Team" project (Y20222023). Conflict of interest statement for all authors The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Ethical approval This study was approved by the Ethics Committee of Affiliated Women’s Hospital of Jiangnan University (2023-06-1213-65). Consent to participate Informed consent was obtained from all individual participants included in the study. Acknowledgements The authors would like to thank all the person and their families for participating and supporting this study. References Harris, E., Infertility Affects 1 in 6 People Globally. Jama, 2023; doi: 10.1001/jama.2023.6251. Zhou, X., X. Liu, W. Shi, M. 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Zhang, et al., The pregnancy outcomes of infertile women with polycystic ovary syndrome undergoing intrauterine insemination with different attempts of previous ovulation induction. Front Endocrinol (Lausanne), 2022; doi: 10.3389/fendo.2022.922605. Luo, X., L. Li, N. Lin, R. Ma, Y. Li, and Z. Wu, Low Endogenous LH on the COS Initiation Day of a GnRH-Agonist Regimen Increases the Risk of Early Pregnancy Loss and Adverse ART Outcomes. Front Endocrinol (Lausanne), 2022; doi: 10.3389/fendo.2022.830567. Xu, H., G. Feng, Y. Wei, Y. Feng, R. Yang, L. Wang, et al., Predicting Ectopic Pregnancy Using Human Chorionic Gonadotropin (hCG) Levels and Main Cause of Infertility in Women Undergoing Assisted Reproductive Treatment: Retrospective Observational Cohort Study. JMIR Med Inform, 2020; doi: 10.2196/17366. Smith, M.B. and R.J. Paulson, Endometrial preparation for third-party parenting and cryopreserved embryo transfer. Fertil Steril, 2019; doi: 10.1016/j.fertnstert.2019.02.010. Zhou, Q., G. Yan, L. Ding, J. Liu, X. Yu, S. Kong, et al., EHD1 impairs decidualization by regulating the Wnt4/β-catenin signaling pathway in recurrent implantation failure. EBioMedicine, 2019; doi: 10.1016/j.ebiom.2019.10.018. Gao, W., Y.B. Sun, W.W. Zhou, Z.J. Xiong, L. Chen, H. Li, et al., Genomic and transcriptomic investigations of the evolutionary transition from oviparity to viviparity. Proc Natl Acad Sci U S A, 2019; doi: 10.1073/pnas.1816086116. Bulletti, C., F.M. Bulletti, R. Sciorio, and M. Guido, Progesterone: The Key Factor of the Beginning of Life. Int J Mol Sci, 2022; doi: 10.3390/ijms232214138. Wang, Z., Y. Gao, D. Zhang, Y. Li, L. Luo, and Y. Xu, Predictive value of serum β-human chorionic gonadotropin for early pregnancy outcomes. Arch Gynecol Obstet, 2020; doi: 10.1007/s00404-019-05388-2. Tapia-Pizarro, A., S. Archiles, F. Argandoña, C. Valencia, K. Zavaleta, M. Cecilia Johnson, et al., hCG activates Epac-Erk1/2 signaling regulating Progesterone Receptor expression and function in human endometrial stromal cells. Mol Hum Reprod, 2017; doi: 10.1093/molehr/gax015. Du, Y., L. Yan, M. Sun, Y. Sheng, X. Li, Z. Feng, et al., Effect of Human Chorionic Gonadotropin Injection Before Frozen Embryo Transfer on Pregnancy Outcomes in Endometriosis-Associated Infertility. Front Med (Lausanne), 2020; doi: 10.3389/fmed.2020.592921. Koch, Y., P. Wimberger, and R. Grümmer, Human chorionic gonadotropin induces decidualization of ectopic human endometrium more effectively than forskolin in an in-vivo endometriosis model. Exp Biol Med (Maywood), 2018; doi: 10.1177/1535370218782658. Melnick, A.P., N. Pereira, E.M. Murphy, Z. Rosenwaks, and S.D. Spandorfer, How low is too low? Cycle day 28 estradiol levels and pregnancy outcomes. Fertil Steril, 2016; doi: 10.1016/j.fertnstert.2015.11.046. Banciu, A., D.D. Banciu, C.C. Mustaciosu, M. Radu, D. Cretoiu, J. Xiao, et al., Beta-Estradiol Regulates Voltage-Gated Calcium Channels and Estrogen Receptors in Telocytes from Human Myometrium. Int J Mol Sci, 2018; doi: 10.3390/ijms19051413. Csapo, A.I., M.O. Pulkkinen, B. Ruttner, J.P. Sauvage, and W.G. Wiest, The significance of the human corpus luteum in pregnancy maintenance. I. Preliminary studies. Am J Obstet Gynecol, 1972; doi: 10.1016/0002-9378(72)90181-0. Ma, W.G., H. Song, S.K. Das, B.C. Paria, and S.K. Dey, Estrogen is a critical determinant that specifies the duration of the window of uterine receptivity for implantation. Proc Natl Acad Sci U S A, 2003; doi: 10.1073/pnas.0530162100. Yuan, L., L. Yu, Z. Sun, J. Song, J. Xiao, H. Jiang, et al., Association between 7-day serum β-hCG levels after frozen-thawed embryo transfer and pregnancy outcomes: a single-centre retrospective study from China. BMJ Open, 2020; doi: 10.1136/bmjopen-2019-035332. Zhang, Y., Z. Li, B. Ren, W. Wu, Y. Liu, X. Wang, et al., Diagnostic value of a single β-hCG test in predicting reproductive outcomes in women undergoing cleavage embryo transfer: a retrospective analysis from a single center. Reprod Health, 2022; doi: 10.1186/s12978-022-01455-1. Sung, N., J. Kwak-Kim, H.S. Koo, and K.M. Yang, Serum hCG-β levels of postovulatory day 12 and 14 with the sequential application of hCG-β fold change significantly increased predictability of pregnancy outcome after IVF-ET cycle. J Assist Reprod Genet, 2016; doi: 10.1007/s10815-016-0744-y. Kommagani, R., M.M. Szwarc, Y.M. Vasquez, M.C. Peavey, E.C. Mazur, W.E. Gibbons, et al., The Promyelocytic Leukemia Zinc Finger Transcription Factor Is Critical for Human Endometrial Stromal Cell Decidualization. PLoS Genet, 2016; doi: 10.1371/journal.pgen.1005937. Gao, S., X. Yang, X. Xiao, S. Yin, Y. Guan, J. Chen, et al., Outcomes and affecting factors for ICSI and microTESE treatments in nonobstructive azoospermia patients with different etiologies: A retrospective analysis. Front Endocrinol (Lausanne), 2022; doi: 10.3389/fendo.2022.1006208. Vicdan, K. and A. Zeki Isik, Luteal phase hormonal profile in prediction of pregnancy outcome after assisted reproduction. Eur J Obstet Gynecol Reprod Biol, 2001; doi: 10.1016/s0301-2115(00)00400-0. Sonntag, B., K.C. Loebbecke, J.R. Nofer, L. Kiesel, and R.R. Greb, Serum estradiol and progesterone in the mid-luteal phase predict clinical pregnancy outcome in IVF/ICSI cycles. Gynecol Endocrinol, 2013; doi: 10.3109/09513590.2013.797392. Gruber, I., A. Just, M. Birner, and A. Lösch, Serum estradiol/progesterone ratio on day of embryo transfer may predict reproductive outcome following controlled ovarian hyperstimulation and in vitro fertilization. J Exp Clin Assist Reprod, 2007; doi: 10.1186/1743-1050-4-1. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 24 Mar, 2024 Reviews received at journal 16 Mar, 2024 Reviewers agreed at journal 16 Mar, 2024 Reviewers invited by journal 15 Mar, 2024 Editor assigned by journal 12 Mar, 2024 Submission checks completed at journal 11 Mar, 2024 First submitted to journal 11 Mar, 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. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4078359","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":278962309,"identity":"4612a2c2-5d47-4554-8709-9e354ba1f86d","order_by":0,"name":"Man Wu","email":"","orcid":"","institution":"Affiliated Women’s Hospital of Jiangnan University","correspondingAuthor":false,"prefix":"","firstName":"Man","middleName":"","lastName":"Wu","suffix":""},{"id":278962310,"identity":"68ed97c7-20f6-4aff-9292-deb2dd0412ff","order_by":1,"name":"Xiao Xiao","email":"","orcid":"","institution":"Affiliated Women’s Hospital of Jiangnan University","correspondingAuthor":false,"prefix":"","firstName":"Xiao","middleName":"","lastName":"Xiao","suffix":""},{"id":278962311,"identity":"2e69cff4-07ac-4544-8119-02508399728d","order_by":2,"name":"Chen Wang","email":"","orcid":"","institution":"Affiliated Women’s Hospital of Jiangnan University","correspondingAuthor":false,"prefix":"","firstName":"Chen","middleName":"","lastName":"Wang","suffix":""},{"id":278962312,"identity":"59ec5129-a60e-4f0d-aa24-7b1fb23ebcec","order_by":3,"name":"Min Zhao","email":"","orcid":"","institution":"Affiliated Women’s Hospital of Jiangnan University","correspondingAuthor":false,"prefix":"","firstName":"Min","middleName":"","lastName":"Zhao","suffix":""},{"id":278962313,"identity":"2c244a3d-39aa-427d-9ac7-8c852e984855","order_by":4,"name":"Fang Xiong","email":"","orcid":"","institution":"Affiliated Women’s Hospital of Jiangnan 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Zheng","email":"data:image/png;base64,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","orcid":"","institution":"Affiliated Women’s Hospital of Jiangnan University","correspondingAuthor":true,"prefix":"","firstName":"Xiaomin","middleName":"","lastName":"Zheng","suffix":""}],"badges":[],"createdAt":"2024-03-11 22:07:50","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4078359/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4078359/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":52709556,"identity":"0c969515-2ff9-4797-81ec-7edfc5fd9131","added_by":"auto","created_at":"2024-03-14 19:46:15","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":55721,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-4078359/v1/114bf7f79400c606beace9cd.png"},{"id":52709555,"identity":"3515986a-f416-44dd-a306-ed1d6dc51954","added_by":"auto","created_at":"2024-03-14 19:46:15","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":58049,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-4078359/v1/ae74b051488e7c8313572a61.png"},{"id":52710830,"identity":"45341965-612e-4ad5-b1aa-d6da33a9a71f","added_by":"auto","created_at":"2024-03-14 19:54:16","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":664623,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4078359/v1/230ee963-9330-4b36-9d74-b264dff6f812.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Combined analysis of estradiol and β-hCG to predict the early pregnancy outcome of FET: a retrospective study","fulltext":[{"header":"Background","content":"\u003cp\u003eInfertility affects one in six people globally[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], which affects approximately 13 hundred million people globally and 1.3 hundred million people in China. In vitro fertilization-embryo transfer (IVF-ET) is currently the most commonly used assisted reproductive techniques (ART). Although IVF success rates are substantially higher today than a few years ago as remarkable advances have been made in in recent years, it\u0026rsquo;s still a challenging issue in clinical IVF practice, due to the variable effects factors such as man\u0026rsquo;s sperm condition, maternal age, cause of infertility, embryo status, endometrial receptivity, reproductive history, lifestyle factors and so on[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Then how to accurately predicting the outcome of an IVF cycle has emerged as a particularly important clinical problem that needs to be solved urgently.\u003c/p\u003e \u003cp\u003eThe clinicians usually use the combination of β-human chorionic gonadotropin (β-hCG) and progesterone (P) to predict the prognosis of pregnancy outcomes in women who conceived naturally or via ART[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. However, conflicts about how to predict adverse pregnancy outcome, such as biochemical pregnancy so that to promote a safe transition of clinical pregnancy and avoid biochemical pregnancy has been challenged for many years.\u003c/p\u003e \u003cp\u003eThe role of estradiol (E\u003csub\u003e2\u003c/sub\u003e) is well documented in IVF cycles, particularly in fertilization and implantation. Many research in hints that successful IVF and a healthy pregnancy is associated with the levels of estrogen. Currently, a number of studies suggested that levels of hormones such as E\u003csub\u003e2\u003c/sub\u003e may play a role in predicting successful pregnancy in IVF cycles[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], but these results are controversial[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. What\u0026rsquo;s more, most previous studies paid attention to the association of clinical outcomes with E\u003csub\u003e2\u003c/sub\u003e on the day of β-hCG administration, or E\u003csub\u003e2\u003c/sub\u003e related with fresh embryo transplantation. However, rare study investigated earlier serum E\u003csub\u003e2\u003c/sub\u003e levels on day 12 after FET with NCs and lately clinical pregnancy outcomes.\u003c/p\u003e \u003cp\u003eAs we know endometrial preparation protocol can mainly be divided into hormonal replacement treatment cycles (HRTs), ovarian stimulation cycle(GnRH-a) and NCs, which is an important factor affecting the pregnancy rate of FET[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], and so we wondered if serum E\u003csub\u003e2\u003c/sub\u003e levels are associated with successful clinical pregnancy of FET. To rule out the effects of hormone supplementation, we just focused on infertile women undergoing FET with NCs group.\u003c/p\u003e \u003cp\u003eTherefore, we undertook this retrospective study and evaluated the predictive value for earlier serum E\u003csub\u003e2\u003c/sub\u003e and β-hCG on the 12th day after FET with NCs. In this research, the association between E\u003csub\u003e2\u003c/sub\u003e level and clinical outcomes in infertility women underwent FET with NCs will be investigated, and we also hope to establish E\u003csub\u003e2\u003c/sub\u003e cutoff values for the prediction of clinical pregnancy earlier on day 12 after FET. So that the doctors could evaluated the lately outcomes in advance and could have more accurent index, in order to provide patients with necessary individualized treatments before the real gestational sac can be documented by ultrasound 28\u0026ndash;35 days after FET[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Besides that, we can reduce the number of patient visits and serum hormone tests, which will decrease psychological and economic stress of patients.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003e All procedures in this study were approved by the Ethics Committee of Affiliated Women\u0026rsquo;s Hospital of Jiangnan University(2023-06-1213-65).\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eCohort selection\u003c/h2\u003e \u003cp\u003e In this retrospective study, infertile women ongoing FET with NCs were collected according to the electronic based medical records of patients from 2012 to 2022.\u003c/p\u003e \u003cp\u003eClinical characteristics included maternal age at diagnosis, nationality, the years of infertility, body mass index (BMI), basal estradiol (bE\u003csub\u003e2\u003c/sub\u003e), basal follicle-stimulating hormone (bFSH) and basal luteinizing hormone (bLH), anti-M\u0026uuml;llerian hormone (AMH), basal prolactin (bPRL), β-hCG and so on. Weight and height at time of diagnosis were measured by BMI calculated and classified according to the ethnicity-specific WHO classification for Asian/Indian women: underweight (under 18.4 kg/m\u003csup\u003e2\u003c/sup\u003e), normal weight (18.5-22.99 kg/m\u003csup\u003e2\u003c/sup\u003e), overweight (23\u0026ndash;27.49 kg/m\u003csup\u003e2\u003c/sup\u003e), and obese (over 27.50 kg/m\u003csup\u003e2\u003c/sup\u003e)[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe study included the patients with age of no more than 35 years old and without major system disease. We excluded the patients with uterine malformation, uterine fibroids or adenomyosis, severely damaged endometrium and chromosomal abnormalities of either part of the couple. Patients with incomplete basic endocrine parameters and untimely β-hCG and E\u003csub\u003e2\u003c/sub\u003e data were also excluded. The patients whose endometrium was less than 8 mm were not included. Finally, 1521 cycles with β-hCG positive were collected. The data was divided into two groups which are CE Group (n\u0026thinsp;=\u0026thinsp;595) and B Group (n\u0026thinsp;=\u0026thinsp;926).\u003c/p\u003e \u003cp\u003eWe then subdivided CE Group to clinical pregnancy group (CE-CP Group, with gestational sac) and biochemical pregnancy group (CE-BP Group, without gestational sac) according to the β-hCG positive (β-hCG\u0026thinsp;\u0026ge;\u0026thinsp;5 mIU/mL) data 12 day after FET[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. B Group was samely divided into blastocyst-clinical pregnancy group (B-CP Group) and blastocyst-biochemical pregnancy group (B-BP Group).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eTreatment protocols and outcome variables assessed\u003c/h2\u003e \u003cp\u003eThe patients who had a history of spontaneous ovulation were recruited and they were carried out FET with NCs. The FET was performed until the endometrium was not less than 8 mm. The number of embryos to transfer (one or two) were determined according to embryo quality, patient age, uterine condition and so on.\u003c/p\u003e \u003cp\u003ePregnancy outcomes were as follows: biochemical pregnancy, clinical pregnancy, ongoing pregnancy, and live birth[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Biochemical pregnancy was defined by serum β-hCG positive test[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], and that fails to progress to the point of ultrasound confirmation of gestational sac 28\u0026ndash;35 days after embryo transfer. While clinical pregnancy was defined by presenting gestational sac using ultrasound scan after embryo transfer. So, in other words, biochemical pregnancy was the pregnancy which doesn\u0026rsquo;t end up with clinical pregnancy. On the morning of cycle day 12 after embryo transfer, blood was drawn and serum E\u003csub\u003e2\u003c/sub\u003e and β-hCG were measured. Our choice of post-ET day 12 is based on the fact that most of our patients had their first serum samples collected on this day. If the serum β-hCG value was \u0026ge;\u0026thinsp;5 mIU/mL, it was considered as biochemical pregnancy[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], and those at least one gestational sac can be documented by ultrasound 28\u0026ndash;35 days after transfer were count as clinical pregnancy.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eIBM SPSS Statistics for Windows Version 27.0 (Armonk, NY: IBM Corp) software was used to analyze all the data. And the continuous data were calculated as mean and standard deviation (̄x\u0026thinsp;\u0026plusmn;\u0026thinsp;s), the difference was assessed using T-test. Spearman\u0026rsquo;s rank correlation (\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e) was used to examine the correlation between day 12 E\u003csub\u003e2\u003c/sub\u003e and β-hCG levels.\u003c/p\u003e \u003cp\u003eROC curve analysis was applied to assess the predictive accuracy of day 12 E\u003csub\u003e2\u003c/sub\u003e and β-hCG levels. ROC curves were generated by joining points defined by sensitivity (true-positive fraction) and corresponding 1-specificity (false-positive fraction) values. The percentage for AUC and 95% confidence intervals were reported for each ROC curve analysis. AUC measures the diagnostic accuracy of the test, with a greater area corresponding to a greater ability to discriminate between patients with clinical pregnancy or not. AUC\u0026thinsp;\u0026lt;\u0026thinsp;0.5 indicated no predictive value, 0.5\u0026thinsp;\u0026le;\u0026thinsp;AUC\u0026thinsp;\u0026lt;\u0026thinsp;0.7 indicated a low predictive value, 0.7\u0026thinsp;\u0026le;\u0026thinsp;AUC\u0026thinsp;\u0026lt;\u0026thinsp;0.9 indicated a moderate prediction value and 0.9\u0026thinsp;\u0026le;\u0026thinsp;AUC\u0026thinsp;\u0026lt;\u0026thinsp;1 indicated a high predictive value.\u003c/p\u003e \u003cp\u003eUnivariate logistic regression analyses were used to study the association between variables (day 12 E\u003csub\u003e2\u003c/sub\u003e levels and day 12 β-hCG concentration) and pregnancy outcome.\u003c/p\u003e \u003cp\u003eStatistical significance was set at a two-sided P\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eGeneral characteristics of the included patients\u003c/h2\u003e \u003cp\u003eThe general characteristics of the included patients are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. There were 1521 cycles of β-hCG positive which consists of 595 cycles with CE Group and 926 cycles with B Group. General characteristics in age, duration of infertility, BMI, AMH, bFSH, bE\u003csub\u003e2\u003c/sub\u003e, bPRL and bLH were compared between CE-CP Group, CE-BP Group and B-CP Group, B-BP Group respectively. Significant differences were observed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Groups are similar in age, duration of infertility, BMI, AMH, bFSH, bE\u003csub\u003e2\u003c/sub\u003e, bPRL and bLH.\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\u003eGeneral characteristics of the included patients\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" 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=\"\u0026plusmn;\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eCharacteristic\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"8\" nameend=\"c9\" namest=\"c2\"\u003e \u003cp\u003eGroup (n\u0026thinsp;=\u0026thinsp;1521)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e \u003cp\u003eCE Group (n\u0026thinsp;=\u0026thinsp;595)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c9\" namest=\"c6\"\u003e \u003cp\u003eB Group (n\u0026thinsp;=\u0026thinsp;926)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCE-CP Group (n\u0026thinsp;=\u0026thinsp;501)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCE-BP Group (n\u0026thinsp;=\u0026thinsp;94)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003et/χ2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eB-CP Group (n\u0026thinsp;=\u0026thinsp;759)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eB-BP Group (n\u0026thinsp;=\u0026thinsp;167)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003et/χ2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\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 (̄x\u0026thinsp;\u0026plusmn;\u0026thinsp;s)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e29.90\u0026thinsp;\u0026plusmn;\u0026thinsp;3.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e30.33\u0026thinsp;\u0026plusmn;\u0026thinsp;3.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.203\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.229\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e30.27\u0026thinsp;\u0026plusmn;\u0026thinsp;2.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e30.71\u0026thinsp;\u0026plusmn;\u0026thinsp;3.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e1.779\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.076\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDuration of infertility (years, ̄x\u0026thinsp;\u0026plusmn;\u0026thinsp;s)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e3.83\u0026thinsp;\u0026plusmn;\u0026thinsp;2.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e4.38\u0026thinsp;\u0026plusmn;\u0026thinsp;2.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.806\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.073\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e4.32\u0026thinsp;\u0026plusmn;\u0026thinsp;2.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e4.38\u0026thinsp;\u0026plusmn;\u0026thinsp;2.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.264\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.792\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI (̄x\u0026thinsp;\u0026plusmn;\u0026thinsp;s, kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e21.63\u0026thinsp;\u0026plusmn;\u0026thinsp;2.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e21.07\u0026thinsp;\u0026plusmn;\u0026thinsp;2.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-1.857\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.064\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e21.71\u0026thinsp;\u0026plusmn;\u0026thinsp;2.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e21.46\u0026thinsp;\u0026plusmn;\u0026thinsp;2.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e-1.007\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.314\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ebFSH (mIU/mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e7.45\u0026thinsp;\u0026plusmn;\u0026thinsp;2.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e7.01\u0026thinsp;\u0026plusmn;\u0026thinsp;2.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-1.918\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.056\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e7.22\u0026thinsp;\u0026plusmn;\u0026thinsp;2.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e7.29\u0026thinsp;\u0026plusmn;\u0026thinsp;2.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.352\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.725\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ebE\u003csub\u003e2\u003c/sub\u003e (pg/mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e36.33\u0026thinsp;\u0026plusmn;\u0026thinsp;26.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e41.18\u0026thinsp;\u0026plusmn;\u0026thinsp;17.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.684\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.093\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e38.20\u0026thinsp;\u0026plusmn;\u0026thinsp;18.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e40.31\u0026thinsp;\u0026plusmn;\u0026thinsp;21.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e1.320\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.187\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ebPRL (ng/mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e15.32\u0026thinsp;\u0026plusmn;\u0026thinsp;7.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e15.29\u0026thinsp;\u0026plusmn;\u0026thinsp;7.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.036\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.971\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e15.11\u0026thinsp;\u0026plusmn;\u0026thinsp;6.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e14.93\u0026thinsp;\u0026plusmn;\u0026thinsp;6.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e-0.331\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.740\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ebLH (mIU/mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e4.82\u0026thinsp;\u0026plusmn;\u0026thinsp;3.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e4.60\u0026thinsp;\u0026plusmn;\u0026thinsp;1.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.552\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.581\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e5.43\u0026thinsp;\u0026plusmn;\u0026thinsp;4.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e5.13\u0026thinsp;\u0026plusmn;\u0026thinsp;3.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e-0.812\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.417\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAMH (ng/mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e4.08\u0026thinsp;\u0026plusmn;\u0026thinsp;2.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e3.68\u0026thinsp;\u0026plusmn;\u0026thinsp;2.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-1.387\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.166\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e4.33\u0026thinsp;\u0026plusmn;\u0026thinsp;2.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e4.11\u0026thinsp;\u0026plusmn;\u0026thinsp;2.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e-0.950\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.342\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"9\"\u003eBMI\u0026thinsp;=\u0026thinsp;body mass index; AMH\u0026thinsp;=\u0026thinsp;anti-M\u0026uuml;llerian hormone; bfsh\u0026thinsp;=\u0026thinsp;basal follicle-stimulating hormone; bE\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;basal estradiol; bPRL\u0026thinsp;=\u0026thinsp;basal prolactin; bLH\u0026thinsp;=\u0026thinsp;basal luteinizing hormone; B-CP\u0026thinsp;=\u0026thinsp;blastocyst-clinical pregnancy; B-BP\u0026thinsp;=\u0026thinsp;blastocyst-biochemical pregnancy; CE-CP\u0026thinsp;=\u0026thinsp;cleavage embryo-clinical pregnancy; CE-BP\u0026thinsp;=\u0026thinsp;cleavage embryo-biochemical pregnancy.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eHormone profile of serum E\u003csub\u003e2\u003c/sub\u003e and β-hCG were significantly higher in clinical pregnancy\u003c/h2\u003e \u003cp\u003eThe serum E\u003csub\u003e2\u003c/sub\u003e levels were compared among all groups on the 12th day after FET with NCs. We found significantly higher serum E\u003csub\u003e2\u003c/sub\u003e levels in CE-CP Group compared with CE-BP Group (212.04\u0026thinsp;\u0026plusmn;\u0026thinsp;151.27 vs 121.18\u0026thinsp;\u0026plusmn;\u0026thinsp;43.18 pg/mL, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Furthermore, the difference between B-CP Group B-BP Group was also significant (215.06\u0026thinsp;\u0026plusmn;\u0026thinsp;96.80 vs 135.87\u0026thinsp;\u0026plusmn;\u0026thinsp;55.20, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). In this analysis, there was also significantly difference in β-hCG level on day 12 after FET with NCs between CE-CP Group and CE-BP Group (β-hCG, 474.73\u0026thinsp;\u0026plusmn;\u0026thinsp;351.88 vs 69.18\u0026thinsp;\u0026plusmn;\u0026thinsp;43.41 mIU/mL, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The same was true in B Group for β-hCG level (832.88\u0026thinsp;\u0026plusmn;\u0026thinsp;694.36 vs 107.49\u0026thinsp;\u0026plusmn;\u0026thinsp;88.44 mIU/mL, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001) on day 12 after FET with NCs.\u003c/p\u003e \u003cp\u003eThe average number of embryos transferred in CE-CP Group, CE-BP Group, B-CP Group\u003c/p\u003e \u003cp\u003eand B-BP Group were 1.91, 1.89, 1.53 and 1.46 respectively, there were no significant difference between CE-CP Group and CE-BP Group (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05), and the same to B-CP Group and B-BP Group (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Between CE-CP Group and CE-BP Group, the difference was not significant in terms of number of top-quality embryos transferred (1.60\u0026thinsp;\u0026plusmn;\u0026thinsp;0.69 vs 1.53\u0026thinsp;\u0026plusmn;\u0026thinsp;0.74, P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). The difference was the same in B-CP Group and B-BP Group (1.00\u0026thinsp;\u0026plusmn;\u0026thinsp;0.68 vs 0.89\u0026thinsp;\u0026plusmn;\u0026thinsp;0.66, P\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). As to the endometrial thickness for transferring embryo, the mean was similar in patients of CE Group (10.17\u0026thinsp;\u0026plusmn;\u0026thinsp;1.71 vs 10.04\u0026thinsp;\u0026plusmn;\u0026thinsp;1.74, P\u0026thinsp;\u0026gt;\u0026thinsp;0.05) and B Group (10.25\u0026thinsp;\u0026plusmn;\u0026thinsp;1.68 vs 10.40\u0026thinsp;\u0026plusmn;\u0026thinsp;1.81, P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\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\u003eCycle parameters and day 12 serum E\u003csub\u003e2\u003c/sub\u003e and β-hCG levels after FET with NCs\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"10\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" 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=\"\u0026plusmn;\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eCycle parameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"9\" nameend=\"c10\" namest=\"c2\"\u003e \u003cp\u003eGroup (n\u0026thinsp;=\u0026thinsp;1521)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e \u003cp\u003eCE Group (n\u0026thinsp;=\u0026thinsp;595)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c10\" namest=\"c6\"\u003e \u003cp\u003eB Group (n\u0026thinsp;=\u0026thinsp;926)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCE-CP Group (n\u0026thinsp;=\u0026thinsp;501)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCE-BP Group (n\u0026thinsp;=\u0026thinsp;94)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003et/χ2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eB-CP Group (n\u0026thinsp;=\u0026thinsp;759)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eB-BP Group (n\u0026thinsp;=\u0026thinsp;167)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003et/χ2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"1\" nameend=\"c10\" namest=\"c10\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003enumber of embryos transferred\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e1.91\u0026thinsp;\u0026plusmn;\u0026thinsp;0.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e1.89\u0026thinsp;\u0026plusmn;\u0026thinsp;0.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.249\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.803\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e1.53\u0026thinsp;\u0026plusmn;\u0026thinsp;0.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e1.46\u0026thinsp;\u0026plusmn;\u0026thinsp;0.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e-1.730\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.084\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c10\" namest=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003enumber of top-quality embryos transferred\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e1.60\u0026thinsp;\u0026plusmn;\u0026thinsp;0.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e1.53\u0026thinsp;\u0026plusmn;\u0026thinsp;0.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.854\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.393\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e1.00\u0026thinsp;\u0026plusmn;\u0026thinsp;0.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e0.89\u0026thinsp;\u0026plusmn;\u0026thinsp;0.66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e-1.922\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.055\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c10\" namest=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEndometrial thickness (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e10.17\u0026thinsp;\u0026plusmn;\u0026thinsp;1.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e10.04\u0026thinsp;\u0026plusmn;\u0026thinsp;1.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.683\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.495\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e10.25\u0026thinsp;\u0026plusmn;\u0026thinsp;1.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e10.40\u0026thinsp;\u0026plusmn;\u0026thinsp;1.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e1.408\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.295\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c10\" namest=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDay 12 E\u003csub\u003e2\u003c/sub\u003e levels after FET (pg/mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e212.04\u0026thinsp;\u0026plusmn;\u0026thinsp;151.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e112.18\u0026thinsp;\u0026plusmn;\u0026thinsp;43.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-12.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e215.06\u0026thinsp;\u0026plusmn;\u0026thinsp;96.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e135.87\u0026thinsp;\u0026plusmn;\u0026thinsp;55.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e-14.317\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c10\" namest=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDay 12 β-hCG levels after FET (mIU/mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e474.73\u0026thinsp;\u0026plusmn;\u0026thinsp;351.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e69.18\u0026thinsp;\u0026plusmn;\u0026thinsp;43.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-24.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e832.88\u0026thinsp;\u0026plusmn;\u0026thinsp;694.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e107.49\u0026thinsp;\u0026plusmn;\u0026thinsp;88.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e-27.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"1\" nameend=\"c10\" namest=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"10\"\u003eB-CP\u0026thinsp;=\u0026thinsp;blastocyst-clinical pregnancy; B-BP\u0026thinsp;=\u0026thinsp;blastocyst-biochemical pregnancy; CE-CP\u0026thinsp;=\u0026thinsp;cleavage embryo-clinical pregnancy; CE-BP\u0026thinsp;=\u0026thinsp;cleavage embryo-biochemical pregnancy; FET\u0026thinsp;=\u0026thinsp;frozen-warmed embryo transfer; NCs\u0026thinsp;=\u0026thinsp;natural endometrial preparation cycles; E\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;estradiol\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eAUC analysis hormone profile of serum E\u003c/b\u003e \u003csub\u003e \u003cb\u003e2\u003c/b\u003e \u003c/sub\u003e \u003cb\u003eand β-hCG levels in predicting clinical pregnancy after FET with NCs\u003c/b\u003e\u003c/p\u003e \u003cp\u003eThe ability of serum E\u003csub\u003e2\u003c/sub\u003e and β-hCG levels to predicting transplant outcomes was evaluated by the AUC analysis (Fig.\u0026nbsp;2). For CE Group, serum E\u003csub\u003e2\u003c/sub\u003e levels were associated with a moderate probability of clinical pregnancy (AUC\u0026thinsp;=\u0026thinsp;0.801, sensitivity\u0026thinsp;=\u0026thinsp;74.45%, specificity\u0026thinsp;=\u0026thinsp;71.28%, cutoff value\u0026thinsp;=\u0026thinsp;129.25 mIU/mL). In terms of β-hCG, the cutoff value was 156.60 mIU/mL to predict clinical pregnancy, with sensitivity of 84.20%, specificity of 95.74% and high predictive value for clinical pregnancy.\u003c/p\u003e \u003cp\u003eFor B Group, the cutoff values for E\u003csub\u003e2\u003c/sub\u003e and β-hCG were 174.45 pg/mL and 217.70 mIU/mL, separately to predict the probability of clinical pregnancy, with AUCs of 0.762 and 0.924 respectively, with sensitivity of 63.77% and 81.56% respectively, with specificity of 77.84% and 94.01% respectively. The differences were all significant.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eSignificantly relations between day 12 E\u003csub\u003e2\u003c/sub\u003e and β-hCG levels\u003c/h2\u003e \u003cp\u003eSerum day 12 E\u003csub\u003e2\u003c/sub\u003e and β-hCG levels correlated significantly in CE Group (\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e=0.117; P\u0026thinsp;=\u0026thinsp;0.004) and B Group (\u003cem\u003er\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e=0.170; P\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eAssociation between variables and clinical outcome by logistic analyses\u003c/h2\u003e \u003cp\u003eLogistic regression analysis showed day 12 serum levels of E\u003csub\u003e2\u003c/sub\u003e and β-hCG concentrations were the significant predictors of clinical pregnancy (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The analysis revealed that serum E\u003csub\u003e2 day 12\u003c/sub\u003e and β-hCG\u003csub\u003eday 12\u003c/sub\u003e were significantly associated with clinical pregnancy in CE Group [E\u003csub\u003e2 day 12\u003c/sub\u003e: odds ratio (OR) of 0.978 (95% CI 0.972\u0026ndash;0.984); β-hCG\u003csub\u003eday 12\u003c/sub\u003e: OR of 0.979 (95% CI 0.973\u0026ndash;0.984)] and B Group [E\u003csub\u003e2 day 12\u003c/sub\u003e: OR of 0.986 (95% CI 0.983\u0026ndash;0.989); β-hCG\u003csub\u003eday 12\u003c/sub\u003e: OR of 0.988 (95% CI 0.986\u0026ndash;0.991)].\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\u003ePredictive accuracy of serum day 12 E\u003csub\u003e2\u003c/sub\u003e and β-hCG concentrations\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\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=\"left\" 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 \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\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\u003eOdds ratio\u003c/p\u003e \u003cp\u003e(95% CI)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eAUC (95%CI)\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eOptimal cutoffpoint\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003eSensitivity\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003eSpecificity\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003ePrediction of clinical pregnancy of cleavage embryos\u003c/em\u003e\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\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDay 12 E\u003csub\u003e2\u003c/sub\u003e levels (pg/mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.978 (0.972\u0026ndash;0.984)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eP\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.801 (0.756\u0026ndash;0.846)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e129.25 mIU/ml\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e74.45%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e71.28%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDay 12 β-hCG levels (mIU/mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.979 (0.973\u0026ndash;0.984)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eP\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.941 (0.923\u0026ndash;0.959)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e156.60 mIU/ml\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e84.20%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e95.74%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003ePrediction of clinical pregnancy of blastocyst embroys\u003c/em\u003e\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 \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDay 12 E\u003csub\u003e2\u003c/sub\u003e levels (pg/mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.986 (0.983\u0026ndash;0.989)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eP\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.762 (0.726\u0026ndash;0.799)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e174.45 mIU/ml\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e63.77%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e77.84%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDay 12 β-hCG levels (mIU/mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.988 (0.986\u0026ndash;0.991)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eP\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.924 (0.907\u0026ndash;0.941)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e217.70 mIU/ml\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e81.56%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e94.01%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003eCI\u0026thinsp;=\u0026thinsp;confidence interval\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eIVF overcomes many causes of infertility over the past decade, but the embryo implantation rate remained relatively low over the past decade[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. And patients with low β-hCG values are often very anxious about their pregnancy outcomes. Then the problem has highlighted, how to accurately predicting the pregnancy outcomes of an IVF cycle are particularly important. So we calculated this study to analyze the roles of day 12 serum E\u003csub\u003e2\u003c/sub\u003e and β-hCG in predicting the early reproductive outcomes and to determine the cutoff values in women undergoing FET with NCs.\u003c/p\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eHormones involved in regulating uterine changes during placentation\u003c/h2\u003e \u003cp\u003eAs we know multiple steroid hormones and growth factors are involved in regulating uterine changes during placentation[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. In which β-hCG was considered as the most important. Previous research revealed that serum levels of β-hCG plays a key role in predicting clinical pregnancy in IVF cycles[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Undoubtedly, β-hCG is essential for the maintained of pregnancy. Moreover, β-hCG is also involved in the regulation of progesterone expression via the ERK1/2 pathway[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], and promote cytotrophoblast differentiation and endometrial stromal cell decidualization[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. P transforms the E\u003csub\u003e2\u003c/sub\u003e-prepared endometrium into a secretory tissue and creates a hospitable environment for embryo attachment[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Estrogens are essential hormones in uterine physiology[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. At the very early stage of human pregnancy, E\u003csub\u003e2\u003c/sub\u003e is mainly produced by corpus luteum of ovaries until the ovary to placental shift occurs[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], which are needed for successful embryo implantation[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eCurrent clinical pregnancy prediction methods and defaults\u003c/h2\u003e \u003cp\u003eThe combination of β-hCG and P has been used to predict the pregnancy outcomes in women who underwent ART or conceived naturally[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eNormally, serum β-hCG and P are lower in nonpregnant women, and their levels could rise significantly after pregnancy. Yuan, et al.[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] found that β-hCG levels were associated with the number of embryos. But other studies[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] reclaimed that the serum levels of β-hCG was no difference in women transferred with one embryo compared with two embryos. Zhang, et al.[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] proposed that the difference was consistent as to the number of transferring high quality. Wang Z, et al.[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] indicated that elevated serum β-HCG levels resulted in decreased biochemical pregnancy rates, increased multiple rates, and decreased ongoing and ectopic pregnancy rates, while it has no meaningful clinical utility to predict adverse pregnancy outcomes.\u003c/p\u003e \u003cp\u003eThe role of E\u003csub\u003e2\u003c/sub\u003e is well documented in IVF cycles, in particular in fertilization and implantation. Study using mice models showed the variations of E\u003csub\u003e2\u003c/sub\u003e levels plays an important role in determining the window of opportunity for an embryo to attach itself to the uterine wall and begin development[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003cb\u003eClinical outcomes in infertility women underwent FET with NCs.\u003c/b\u003e \u003c/p\u003e \u003cp\u003eUterine decidualization supports embryo implantation and placentation as well as subsequent events, which maintain a successful pregnancy together[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Latest research indicated that endometrial receptivity but not embryo quality is a key factor restricting successful pregnancy after FET.\u003c/p\u003e \u003cp\u003eHRTs, GnRH-a or NCs which were used for the endometrial preparation[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e] can be observed as an important factor affecting the pregnancy rate of FET. To rule out the effect of hormone supplementation, we focus on infertility women underwent FET with NCs, and hope to evaluated the association between E\u003csub\u003e2\u003c/sub\u003e level and clinical outcomes in infertility women underwent FET with NCs.\u003c/p\u003e \u003cp\u003e \u003cb\u003eHormone profile of E\u003c/b\u003e \u003csub\u003e \u003cb\u003e2\u003c/b\u003e \u003c/sub\u003e \u003cb\u003ecombined with β-hCG on day 12 after FET with NCs to evaluated pregnancy outcomes\u003c/b\u003e\u003c/p\u003e \u003cp\u003ePrevious studies have revealed that the levels of E\u003csub\u003e2\u003c/sub\u003e in luteal phase are associated with the outcome of IVF and suggested that E\u003csub\u003e2\u003c/sub\u003e levels of corpus luteum may be able to be a potential predictor of ongoing pregnancy post-clinical pregnancy[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. However, some results are controversial[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Goldman RH et al.[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] found high levels of serum E\u003csub\u003e2\u003c/sub\u003e on the day of progesterone start may be detrimental to implantation, pregnancy, and live birth following FET. Supraphysiologic serum E\u003csub\u003e2\u003c/sub\u003e levels may negatively impact the likelihood of conception and live birth following IVF. A study reported that higher ratio of E\u003csub\u003e2\u003c/sub\u003e and P on the day of embryo transfer has better pregnancy outcome[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. In addition, a most recent study reported that lower E\u003csub\u003e2\u003c/sub\u003e levels in cycle days 28 (22 days after fresh embryo transfer) were associated with pooper pregnancy outcome[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. There are also some other related researches which mostly paid attention to the association of clinical outcomes with E\u003csub\u003e2\u003c/sub\u003e on the day of β-hCG administration, or E\u003csub\u003e2\u003c/sub\u003e related with fresh embryo transplantation. Although previous research has established that E\u003csub\u003e2\u003c/sub\u003e and P regulate events leading to implantation, relatively little is known about their relative proportion in maternal serum during the early luteal phase.\u003c/p\u003e \u003cp\u003eUntil now rare studies investigating the association between the pregnancy outcomes and E\u003csub\u003e2\u003c/sub\u003e on day 12 after FET with NCs.\u003c/p\u003e \u003cp\u003eIn this retrospective cohort study, we investigated the association between E\u003csub\u003e2\u003c/sub\u003e level and clinical outcomes in infertility women underwent FET with NCs, and E\u003csub\u003e2\u003c/sub\u003e cutoff values had been established, which it can combined with β-hCG level on day 12 after FET with NCs to evaluated both positive and adverse pregnancy outcomes.\u003c/p\u003e \u003cp\u003eWe found that E\u003csub\u003e2\u003c/sub\u003e levels were significantly higher in the clinical pregnancy group than in the biochemical pregnancy group on the 12th day after FET with NCs, suggesting a strong link between E\u003csub\u003e2\u003c/sub\u003e levels and clinical outcomes. Low levels of E\u003csub\u003e2\u003c/sub\u003e may affect the development and maturation of endometrial glands and ultimately reduce the clinical pregnancy rate. However, the thresholds at which elevated E\u003csub\u003e2\u003c/sub\u003e levels may adversely affect endometrial receptivity have not yet been elucidated.\u003c/p\u003e \u003cp\u003eWith the serum E\u003csub\u003e2\u003c/sub\u003e level combined with β-hCG on day 12 after FET, the doctors could evaluate the outcomes in advance and could have more accurent index to evaluated both positive and adverse pregnancy outcomes, and then to provide patients with necessary individualized treatments. In addition, we can reduce the number of patient visits and serum hormone tests, which will decrease psychological and economic stress of patients.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eART is an ideal solution for many couples suffering from infertility, and nowadays how to improve the embryo implantation rate has become an appealing topic. The treatment of progesterone has been widely used in clinical treatment to improve the pregnancy outcomes in patients in early pregnancy, and the serum β-hCG values 14 days after embryo transplantation are widely used to predict pregnancy outcomes, while the detection and supplement of estrogen seems to be ignored, here we mainly focus with hormone profile of E\u003csub\u003e2\u003c/sub\u003e combined with β-hCG on day 12 after FET with NCs to evaluate both positive and negative pregnancy outcomes. Our evidence clearly indicates that, biochemical pregnancy is significantly different in serum E\u003csub\u003e2\u003c/sub\u003e level compared with clinical pregnancy after FET with NCs and the E\u003csub\u003e2\u003c/sub\u003e cutoff values for predicting clinical pregnancy after FET with NCs were proposed. Our results from the retrospective cohort study indicates that the cutoff values of E\u003csub\u003e2\u003c/sub\u003e with acceptable sensitivity and specificity for predicting clinical pregnancy were 129.25 pg/mL for CE Group and 174.45 pg/mL for B Group. Earlier E\u003csub\u003e2\u003c/sub\u003e combined with β-hCG on day 12 after FET can be used as a predictor to evaluated both positive and adverse pregnancy outcomes after FET with NCs.\u003c/p\u003e \u003cp\u003eIn conclusion, these findings demonstrate that besides day 12 serum β-hCG concentrations, serum day 12 E\u003csub\u003e2\u003c/sub\u003e levels can also predict clinical pregnancy after FET with NCs. What\u0026rsquo;s more, the value of serum day 12 E\u003csub\u003e2\u003c/sub\u003e and β-hCG levels for predicting clinical pregnancies were equally important. There is a significant correlation between the day 12 E\u003csub\u003e2\u003c/sub\u003e and β-hCG levels. Therefore, the inclusion of day 12 E\u003csub\u003e2\u003c/sub\u003e levels into the panel for routine follow up of FET with NCs pregnancies is justified by our study.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eFET: frozen-warmed embryo transfer; NCs: in natural endometrial preparation cycles;\u0026nbsp;CP Group: clinical pregnancy group; BP Group: biochemical pregnancy group;\u0026nbsp;CE Group:\u0026nbsp;cleavage group;\u0026nbsp;B Group:\u0026nbsp;blastocyst group;\u0026nbsp;IVF-ET: in vitro fertilization-embryo transfer; ART: assisted reproductive techniques; E\u003csub\u003e2\u003c/sub\u003e: estradiol; \u0026beta;-hCG: \u0026beta;-human chorionic gonadotropin; P: progesterone; HRTs: hormonal replacement treatment cycles; GnRH-a: ovarian stimulation cycle; ROC: receiver operating characteristic; AUC: area under the ROC curve; CI: confidence interval.\u003c/p\u003e\n"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eZheng Xiaomin and Zhao Min together conceived and designed the experiments. Wu Man, Xiao Xiao collected the clinical data and performed most of the analysis. Wang Chen analyzed part of the data. Xin Jin contributed the tools for analysis. Wu Man and Zheng Xiaomin drafted the paper. Xiong Fang participated in part of the paper writing and revised. All authors have read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was funded by Jiangsu Province Innovation and Entrepreneurship Program (JSSCRC2021569), Jiangsu Province Medical Distinguished Expert, and Wuxi \u0026quot;Taihu Talent Team\u0026quot; project (Y20222023).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest statement for all authors\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Ethics Committee of Affiliated Women\u0026rsquo;s Hospital of Jiangnan University (2023-06-1213-65).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInformed consent was obtained from all individual participants included in the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank all the person and their families for participating and supporting this study.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eHarris, E., Infertility Affects 1 in 6 People Globally. 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Cecilia Johnson, et al., hCG activates Epac-Erk1/2 signaling regulating Progesterone Receptor expression and function in human endometrial stromal cells. Mol Hum Reprod, 2017; doi: 10.1093/molehr/gax015.\u003c/li\u003e\n\u003cli\u003eDu, Y., L. Yan, M. Sun, Y. Sheng, X. Li, Z. Feng, et al., Effect of Human Chorionic Gonadotropin Injection Before Frozen Embryo Transfer on Pregnancy Outcomes in Endometriosis-Associated Infertility. Front Med (Lausanne), 2020; doi: 10.3389/fmed.2020.592921.\u003c/li\u003e\n\u003cli\u003eKoch, Y., P. Wimberger, and R. Gr\u0026uuml;mmer, Human chorionic gonadotropin induces decidualization of ectopic human endometrium more effectively than forskolin in an in-vivo endometriosis model. Exp Biol Med (Maywood), 2018; doi: 10.1177/1535370218782658.\u003c/li\u003e\n\u003cli\u003eMelnick, A.P., N. Pereira, E.M. Murphy, Z. Rosenwaks, and S.D. Spandorfer, How low is too low? Cycle day 28 estradiol levels and pregnancy outcomes. 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Gynecol Endocrinol, 2013; doi: 10.3109/09513590.2013.797392.\u003c/li\u003e\n\u003cli\u003eGruber, I., A. Just, M. Birner, and A. L\u0026ouml;sch, Serum estradiol/progesterone ratio on day of embryo transfer may predict reproductive outcome following controlled ovarian hyperstimulation and in vitro fertilization. J Exp Clin Assist Reprod, 2007; doi: 10.1186/1743-1050-4-1.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-ovarian-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jovr","sideBox":"Learn more about [Journal of Ovarian Research](http://ovarianresearch.biomedcentral.com)","snPcode":"13048","submissionUrl":"https://submission.nature.com/new-submission/13048/3","title":"Journal of Ovarian Research","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Estradiol, β-hCG, cutoff value, clinical pregnancy, biochemical pregnancy, frozen-warmed embryo transfer","lastPublishedDoi":"10.21203/rs.3.rs-4078359/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4078359/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eHow to accurately predicting the pregnancy outcomes of an IVF cycle are particularly important. Although a lot of work was conducted to predict pregnancy outcomes by assaying serum β-hCG levels after embryo transfer, rare study has focused on the prediction of serum E\u003csub\u003e2\u003c/sub\u003e level after transfer. This study sought to analyze the predictive effect of serum E\u003csub\u003e2\u003c/sub\u003e combined with β-hCG on early reproductive outcomes 12 days after embryo transfer.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eA total of 1521 patients with β-hCG positive values on day 12 after frozen-warmed embryo transfer (FET) in natural endometrial preparation cycles (NCs) were collected in affiliated Women\u0026rsquo;s Hospital of Jiangnan University. Logistic regression analysis was constructed to establish the clinical pregnancy prediction model, and the cutoff value, optimal sensitivity and specificity were calculated by Receiver operating characteristic (ROC).\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eLevels of serum E\u003csub\u003e2\u003c/sub\u003e and β-hCG on the 12th day after FET with NCs were higher in clinical pregnancy group (CP Group) compared with biochemical pregnancy group (BP Group) (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Besides, the cutoff values for E\u003csub\u003e2\u003c/sub\u003e and β-hCG on the 12th day after FET with NCs in cleavage group (CE Group) were 129.25 pg/mL and 156.60 mIU/mL respectively, with area under the ROC curve (AUC) of 0.801 and 0.941 respectively. For blastocyst group (B Group), the cutoff values for E\u003csub\u003e2\u003c/sub\u003e and β-hCG were 174.45 pg/mL and 217.70 mIU/mL, with AUCs of 0.762 and 0.924 respectively. The logistic regression analysis revealed that serum E\u003csub\u003e2 day 12\u003c/sub\u003e and β-hCG\u003csub\u003eday 12\u003c/sub\u003e were significantly associated with clinical pregnancy.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eSerum E\u003csub\u003e2\u003c/sub\u003e is significantly different in CP Group compared with BP Group in FET with NCs. Earlier E\u003csub\u003e2\u003c/sub\u003e combined with β-HCG can be used as a predictor of early pregnant state.\u003c/p\u003e","manuscriptTitle":"Combined analysis of estradiol and β-hCG to predict the early pregnancy outcome of FET: a retrospective study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-14 19:46:10","doi":"10.21203/rs.3.rs-4078359/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-03-24T16:24:53+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-03-16T08:44:07+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"42ee161d-4e4b-49ed-9f97-672964a7cf2d","date":"2024-03-16T06:44:10+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-03-15T22:32:31+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-03-13T00:56:42+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-03-12T03:17:51+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Ovarian Research","date":"2024-03-11T21:50:56+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-ovarian-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jovr","sideBox":"Learn more about [Journal of Ovarian Research](http://ovarianresearch.biomedcentral.com)","snPcode":"13048","submissionUrl":"https://submission.nature.com/new-submission/13048/3","title":"Journal of Ovarian Research","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d51276c5-c3c9-4ee7-81e5-327b8ad7438b","owner":[],"postedDate":"March 14th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2024-05-07T02:38:12+00:00","versionOfRecord":[],"versionCreatedAt":"2024-03-14 19:46:10","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4078359","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4078359","identity":"rs-4078359","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}