Day 3 embryo quality is a predictor for the clinical pregnancy rate and live birth rate in single frozen- thawed poor-quality blastocyst transfer

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Methods: Seven hundred and thirty-four frozen-thawed single blastocyst transfer cycles carried out between January 2018 to October 2021 were retrospectively analyzed. Cycles were categorized into four groups based on embryo grade: G-G group (good-quality blastocysts derived from day 3 good-quality embryos group, n=194), G-P group (good-quality blastocysts derived from day 3 poor-quality embryos group, n=230), P-Ggroup (poor-quality blastocysts derived from day 3 good-quality embryos group, n=94) and P-P group (poor-quality blastocysts derived from day 3 poor-quality embryos group, n=216). The analysis focused on the role of the day 3 embryo quality in selecting single frozen-thawed good- or poor- quality blastocyst for transfer. Results: Good-quality blastocysts derived from day 3 poor-quality embryos had comparable pregnancy outcomes to those derived from day 3 good-quality embryos (clinical pregnancy rates: 63.91% vs. 65.98%; live birth rates: 53.04% vs. 55.15%, respectively P≥0.05). However, poor-quality blastocysts derived from day 3 good-quality embryos exhibited significantly higher clinical pregnancy rates (58.51% vs. 37.96%, P＜0.01; OR 2.006,95% CI 1.185-3.395, P＜0.05) and live birth rates (52.13% vs. 28.70%, P＜0.001; OR 2.318, 95% CI 1.355-3.966, P＜0.01) than those derived from day 3 poor-quality embryos. Conclusion(s): Day 3 embryo quality serves as a predictor for the clinical pregnancy and live birth rate after single frozen-thawed poor-quality blastocyst transfer. When only poor-quality blastocysts are available, selecting those derived from day 3 good-quality embryo for transfer may expedite the process of achieving a live birth. Single blastocyst transfer Day 3 embryo quality Live birth rate Clinical pregnancy rate Introduction It has been well known that single embryo transfer (SET) is the best method for reducing multiple pregnancy rate, resulting in decreased risks for both maternal and neonatal outcomes in assisted reproductive technology (ART) [1-4] . The key of SET is selecting the most viable embryo for transfer to reduce multiple pregnancies while maintaining a high rate of successful pregnancies during in vitro fertilization(IVF) treatment [5,6] . Now, the most commonly used method for evaluating embryo development is still static morphological evaluation. There is evidence that single blastocyst transfer has been shown to yield superior pregnancy outcomes compared to single cleavage-stage embryo transfer [7,8] . Blastocyst morphological grading is a useful method for blastocyst selection, however, its predictive value for pregnancy outcomes is still limited [9- 11] . The study examining chromosomal status of good-quality blastocysts still reports overall aneuploidy rates of 39-57% [12] . Moreover, it is difficult that determining which one has better developmental potential when multiple same grade blastocysts are obtained. Therefore, having effective methods for blastocyst selection is crucial. Day 3 embryo quality is an important evaluation parameter for cleavage stage embryo selection, is it still an important parameter for blastocyst selection? Xia et al [13] indicated that day 3 poor-quality embryos may have a negative impact on the pregnancy outcomes, but it is not clear whether these differences still exist when different quality embryo at day 3 are cultured to same morphological grade blastocysts. Several studies showed that there was controversy regarding the effects of day 3 embryo quality on pregnancy outcomes after single good-quality blastocyst transfer [14-19] . Moreover, as we known, to date, only two studies have analyzed the relationship between day 3 embryo quality and pregnancy outcomes in single poor-quality blastocyst transfer cycles [17,18] . And their results showed that there was no relationship between them. Despite these results, it is still unclear whether and how we should focus attention on day 3 embryo quality when transferring single particular grade frozen- warmed blastocysts, especially poor-quality blastocysts . Therefore, the purpose of our study is to investigate correlation between day 3 embryo quality and the pregnancy outcomes after single good- or poor-quality frozen-thawed blastocyst transfer. It will help us to know the role of day 3 embryo quality in the same grade blastocyst selection. Materials And Methods Patients A retrospective analysis was performed between January 2018 to October 2021 at the Centre for Reproductive Medicine of Guangzhou Women and Children’s Medical Center. Patients undergoing frozen embryo transfer (FET) cycles with single blastocyst transfer were included. The cycle exclusion criteria are as follows: (1) cycles involving preimplantation genetic testing (PGT); (2) cycles involving female aged over 40 years; (3) cycles involving congenital uterine malformations or endometrium <7mm; (4) cycles involving day 7 blastocyst transfer;(5) cycles involving blastocyst accessed as less than 3BC/3CB.The participant selection process is detailed in Fig. 1. Finally, 734 single frozen-thawed blastocyst transfer cycles were analyzed. These cycles were categorized into four groups according to embryo grade: the good-quality blastocysts derived from day 3 good-quality embryos group (G-G group, n=194), the good-quality blastocysts derived from day 3 poor-quality embryos group (G-P group, n=230), the poor-quality blastocysts derived from day 3 good-quality embryos group (P-G group, n=94) and the poor-quality blastocysts derived from day 3 poor-quality embryos group (P-P group, n=216). The primary outcome of the study was the live birth rate (LBR), while the secondary outcomes included clinical pregnancy rate (CPR), miscarriage rate. Cleavage stage embryos and blastocyst scoring Conventional IVF and intracytoplasmic sperm injection (ICSI) procedures were conducted 3-6 hours after oocyte retrieval, followed by a fertilization check at 16-18 hours post-insemination. A zygote with two pronuclei (2PN) and were cultured in G1 TM (Vitrolife, Sweden) under mineral oil. Embryos that underwent extended culture were transferred to G2 TM (Vitrolife, Sweden) on day 3 and cultured until day 5 or 6 under mineral oil. All cultures took place in incubators set at a temperature of 37°C with 6% CO2, 5% O2 and 89% N2. Day 3 embryos were assessed according to the Istanbul consensus [20] . Blastocysts were assessed according to Gardner and Schoolcraft's classification. In our laboratory, day 3 good-quality embryos are characterized by having 7-8 cells on day 3, less than 10% fragmentation, symmetrical blastomeres, and an absence of multinucleation. A good-quality blastocyst was defined as blastocysts of grade 3BB or higher. Blastocyst vitrification and thawing procedures The criterion for cryopreservation and transfer of blastocysts in our study was a blastocyst grade of at least 3BC/3CB. Vitrification was employed for cryopreservation, and the embryos were thawed using a standardized procedure (Jieying thawing medium, Jieying Laboratory Inc., Canada). Embryo transfer and pregnancy Cryopreserved blastocyst transfers were scheduled during either a natural or exogenous steroid replacement cycle, with warmed blastocysts cultured for 2 hours before transfer. Serum HCG levels were assessed 12 days after blastocyst transfer, and clinical pregnancy was defined as the presence of a gestational sac exhibiting fetal heart activity detected via vaginal ultrasound at 7 weeks' gestation. Statistical analysis The statistical analysis was conducted using SPSS 22.0 software. For quantitative data with a normal distribution, Student's t-test was applied, while the Mann-Whitney U test was utilized for quantitative data with an abnormal distribution. Qualitative data underwent testing using the chi-squared test or Fisher's exact test when appropriate. Additionally, a multivariate logistic regression analysis was performed to identify confounding factors independently related to the LBR and CPR. The odds ratio (OR) with 95% confidence intervals (CIs) was calculated. A P value < 0.05 was considered statistically significant. Results The inclusion process of patients is detailed in Fig. 1. From the initial cohort of 1188 single frozen-thewed blastocyst transfer cycles conducted in our reproductive center during the study period, 454 single frozen-thewed blastocyst transfer cycles were excluded for various reasons: PGT cycles (n=364), female age over 40 years (n=41), and cycles with day 7 blastocysts, uterine malformations, or endometrium less than 7mm (n=49). Consequently, a total of 734 single frozen-thewed blastocyst transfer cycles were included. Within this cohort, patients were divided into four groups: G-G group(n=194), G-P group(n=230), P-G group(n=94) and P-P group (n=216). Patient and embryo characteristics of frozen-thawed single good- or poor-quality blastocysts with different day 3 embryo quality As shown in Table 1, no significant differences were observed in female age, female body mass index (BMI), infertility duration, endometrial thickness, infertility types, endometrial preparation, blastocyst frozen day (day 5/6) and degree of expansion (B3/4/5/6) between G-G and G-P groups(P≥0.05). Additional, patient and embryo characteristics were comparable between P-G and P-P groups, except the proportion of vitrified day 5 blastocysts of P-G group was higher than P-P group (74.47% vs. 49.07%, P<0.001). Pregnancy outcomes of frozen-thawed single good- or poor-quality blastocysts with different day 3 embryo quality In Table 2, the CPR (65.98% vs. 63.91%, P≥0.05), abortion rate (14.06% vs. 17.01%, P≥0.05) and LBR (55.15% vs. 53.04%, P≥0.05) did no differ significantly between G-G and G-P groups. The abortion rates were similar between P-G and P-P groups (10.91% vs. 20.73%, P≥0.05), however, the CPR (58.51% vs. 37.96%, P<0.01) and LBR (52.13% vs. 28.70%, P<0.001) of the P-G group were significantly higher than those of the P-P group. The clinical outcomes of the four groups were compared in pairs In Supplementary Fig1, the CPR and LBR of four groups were compared in pairs. The results revealed that the CPR and LBR of the P-P group were significantly lower than those of G-G, G-P, and P-G groups (P<0.01, respectively). However, there were no significant differences in the CPR and LBR among G-G, G-P and P-G groups (P≥0.05, respectively). Multivariate logistic regression analysis Multivariate logistic regression analysis was conducted to examine the variables influencing CPR and LBR of single frozen-thewed poor-quality blastocyst transfer cycles. As presented in Table 3, both day 3 good-quality embryo (OR=2.006 [1.185-3.395], P<0.05) and blastocyst frozen on day 5 (OR=2.128 [1.271-3.562], P<0.01) had a significant positive impact on CPR. Furthermore, age (OR=0.920 [0.855-0.990], P<0.05), endometrial thickness (OR=1.157 [1.005-1.331], P<0.05), day 3 embryo quality (OR=2.318 [1.355-3.966], P<0.01), and blastocyst frozen day (OR=2.472 [1.418-4.307], P<0.01) were found to be significantly associated with LBR. However, the effects of other factors on CPR and LBR did not exhibit significant differences (P≥0.05). Discussion Our finding showed that transferring the single frozen-thewed poor-quality blastocysts derived from day 3 good-quality embryos resulted in higher CPR and LBR compared to those derived from day 3 poor-quality embryos and achieved similar CPR and LBR as the good-quality blastocysts derived from day 3 good- and poor- quality embryos. Previous studies invested that the development potential of good-quality blastocysts from poor-quality cleavage embryos. Kaartinen et al. [21] showed that the CPR of vitrified–warmed good-quality blastocysts derived from poor-quality cleavage embryos was 24.6%, whereas the CPR of vitrified–warmed good-quality cleavage embryos was 29.4%. Sallem et al [22] reported that CPR was 40.8% after extended culture of embryos with poor developmental potential into good-quality blastocyst. In our study, the transfer of good-quality blastocysts from the extended culture of day 3 poor-quality embryos resulted in CPR of 63.91%. These results indicated that the extended culture of poor-quality cleavage embryos can still develop to the blastocyst stage and result in good pregnancy outcomes. This could be explained by embryo plasticity, the proportion of chromosomally abnormal cells varies during the culture, and the corrupted cells can be eliminated resulting in good-quality blastocysts developing from poor-quality cleavage embryos [23] . However, it is not clear whether they have comparable pregnancy outcomes to good-quality cleavage embryos when cultured to the good-quality blastocysts. Therefore, in the present study, we compared the pregnancy outcomes between them. The results showed the CPR, LBR and abortion rate are not influenced by good or poor quality at day 3 when good-quality blastocysts are transferred. The conclusion is in line with previous studies [14-16] . The study indicated that day 3 embryo quality was not a useful predictor for the pregnancy outcomes in single frozen- thawed good-quality blastocysts. As we known, to date, only two studies have analyzed the relationship between day 3 embryo quality and pregnancy outcomes in poor-quality blastocyst transfer cycles [18,19] . Shen et al [18] found that the day 3 embryo grade (I-II, III-IV) did not influence the CPR and LBR in either BC or CB groups after adjusting for confounding factors. Qiu et al [19] showed that the LBR and miscarriage rate of poor-quality blastocyst from day 3 high-grade embryos were similar with those from day 3 poor-grade embryos(LBR:26.1% VS.28.0%;miscarriage rate:6.6% VS.8.3%).In our study, the CPR and LBR of good-quality blastocysts from day 3 good-quality embryos were significantly higher than those from poor-quality embryos, and achieved similar CPR and LBR as the good-quality blastocysts derived from day 3 good- and poor- quality embryos. These discrepancies between our findings and theirs could be attributed, in part, to a different definition of day 3 good-quality embryos. Moreover, the conventional microscopic assessment of embryo morphology still remains inherently subjective, frequently demonstrating significant variability between different observers and even within the same observer [24-26] , thus posing a limitation in this study. Limitations This study is subject to several limitations. Firstly, its retrospective design introduces the potential for residual confounding, as inherent biases may not have been completely addressed. Further validation through prospective studies is necessary to strengthen the reliability of our findings. Secondly, the subjective nature of morphological evaluation constrains the objectivity of our findings. Therefore, efforts to standardize evaluation protocols or incorporate more objective measures may enhance the robustness of future studies in this area. Conclusions In conclusion, our study suggests that day 3 embryo quality is not a useful predictor for the pregnancy outcomes in single frozen-thawed good-quality blastocysts. However, day 3 embryo quality is a strong predictor for the clinical pregnancy rate and live birth rate in single frozen-thawed poor-quality blastocysts. This finding is particularly crucial for patients who only produce poor-quality blastocysts, as it optimizes blastocyst freezing and transfer sequencing, ultimately reducing patients' waiting time to achieve successful live births. Abbreviations SET: single embryo transfer; ART: assisted reproductive technology; IVF: In vitro fertilization; ICSI: Intracytoplasmic sperm injection; FET: frozen embryo transfer; PGT: Preimplantation genetic testing; CPR: Clinical pregnancy rate; LBR: Live birth rate; BMI: body mass index; 2PN: Two pronuclei; HCG: Human Chorionic Gonadotrophin; OR: Odds Ratio; CI: Confidence interval. Declarations Acknowledgements My colleagues for their invaluable input and for being a great source of support to me during this study. Author contributions Shuai Liu, Li Yang contributed to the conception and design of the study. Ling Sun, Minna Yin, Jian Xu and Jun Liu contributed to data interpretation. Wang Hui, Yunhao Liang, Huijiao Wu contributed to data analysis. Yu Jiang, Meiyi Li, and Zhu feng Wu contributed to data acquisition. Li Yang and Minna Yin drafted the first version of the manuscript. Shuai Liu and Zhiheng Chen wrote the final version. The authors read and approved the final manuscript. Funding The study was funded by Guangzhou Health and Technology Project (20221A011036). Data availability The datasets during the current study are available from the corresponding- g author on reasonable request. Ethics approval and consent to participate The study received approval from the Independent Ethics Committee of Guangzhou Women and Children’s Hospital (No.001A01). Consent for publication Not applicable. Competing interests The authors declare no competing interests. References McLernon DJ, Harrild K, Bergh C, Davies MJ, de Neubourg D, Dumoulin JC,et al. Clinical effectiveness of elective single versus double embryo transfer: meta-analysis of individual patient data from randomised trials. BMJ. 2010;341:c6945. Kamath MS, Mascarenhas M, Kirubakaran R, Bhattacharya S.Number of embryos for transfer following in vitro fertilisation or intra-cytoplasmic sperm injection. Cochrane Database Syst Rev.2020;8:CD003416 Reimundo P, Gutiérrez Romero JM, Rodríguez Pérez T, Veiga E. Single-embryo transfer: a key strategy to reduce the risk for multiple pregnancy in assisted human reproduction. Adv Lab Med. 2021;2(2):179-198. Wang Y, Shi H, Chen L, Zheng D, Long X, Zhang Y, et al. Absolute Risk of Adverse Obstetric Outcomes Among Twin Pregnancies After In Vitro Fertilization by Maternal Age. JAMA Netw Open. 2021 Sep 1;4(9): e2123634. 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Blastocysts that came from better quality day 3 embryos give higher pregnancy rates than blastocysts that derive from poor quality day 3 embryos. Ovarian Club, Paris. Shen X, Long H, Gao H, Guo W, Xie Y, Chen D, et al. The Valuable Reference of Live Birth Rate in the Single Vitrified-Warmed BB/BC/CB Blastocyst Transfer: The Cleavage-Stage Embryo Quality and Embryo Development Speed. Front Physiol. 2020; 11:1102. Qiu J, Du T, Guo H, Mol BW, Lin J, Zhao D, et al. Does Day 3 embryo status matter to reproductive outcomes of single blastocyst transfer cycles? A cohort study. BJOG. 2023 Dec;130(13):1669-1676. Alpha Scientists in Reproductive Medicine and ESHRE Special Interest Group of Embryology. The Istanbul consensus workshop on embryo assessment: proceedings of an expert meeting. Hum Reprod. 2011;26(6):1270-83. Kaartinen N, Das P, Kananen K, Huhtala H, Tinkanen H. Can repeated IVF-ICSI-cycles be avoided by using blastocysts developing from poor-quality cleavage stage embryos? Reprod Biomed Online. 2015 ;30(3):241-7. Sallem A, Santulli P, Barraud-Lange V, Le Foll N, Ferreux L, Maignien C, et al. Extended culture of poor-quality supernumerary embryos improves ART outcomes. J Assist Reprod Genet. 2018 ;35(2):311-319. Fragouli E, Alfarawati S, Spath K, Jaroudi S, Sarasa J, Enciso M, et al. The origin and impact of embryonic aneuploidy. Hum Genet. 2013; 132 (9): 1001-13. Paternot G, Wetzels AM, Thonon F, Vansteenbrugge A, Willemen D, Devroe J, et al. Intra- and interobserver analysis in the morphological assessment of early stage embryos during an IVF procedure: a multicentre study. Reprod Biol Endocrinol. 2011; 9:127. Hammond ER, Foong AKM, Rosli N, Morbeck DE. Should we freeze it? Agreement on fate of borderline blastocysts is poor and does not improve with a modified blastocyst grading system. Hum Reprod. 2020 ;35(5):1045-1053. Chiappetta V, Innocenti F, Coticchio G, Ahlström A, Albricci L, Badajoz V,et al . Discard or not discard, that is the question: an international survey across 117 embryologists on the clinical management of borderline quality blastocysts. Hum Reprod. 2023 ;38(10):1901-1909. Tables Table 1 Patient and embryo characteristics of frozen-thawed single good- or poor-quality blastocysts with different day 3 embryo quality Blastocyst quality grades Good-quality blastocyst transfers cycles (n=424) Poor-quality blastocyst transfers cycles (n=310) Groups G-G group (n=194) G-P group (n=230) P1 P-G group (n=94) P -P group (n=216) P2 Cycles 194 230 94 216 Female Age(year) 31.42±3.88 31.50±3.42 0.826 31.80±3.72 32.11±3.63 0.489 Female BMI(kg/m 2 ) 20.93±3.16 21.46±2.89 0.071 21.24±3.29 20.96±3.23 0.481 Duration of infertility(year) 2.55 (1.00,4.00) 2.00 (1.00,3.00) 0.097 2.00 (1.20,3.25) 2.00 (1.20,3.00) 0.754 Endometrial thickness(mm) 9.73±1.64 9.76±1.81 0.876 9.68±1.72 9.88±1.85 0.377 Infertility type 0.409 0.749 Primary infertility 43.81 (85/194) 47.83 (110/230) 43.62 (41/94) 41.67 (90/216) Secondary infertility 56.19 (109/194) 52.17 (120/230) 56.38 (53/94) 58.33 (126/216) Endometrial preparation 0.289 0.165 Natural cycles 10.31 (20/194) 7.39 (17/230) 11.70 (11/94) 6.94 (15/216) Hormone therapy cycles 89.69 (174/194) 92.61 (213/230) 88.30 (83/94) 93.06 (199/216) Blastocyst frozen day 0.737 < 0.001 Day5 82.99 (161/194) 81.74 (188/230) 74.47 (70/94) 49.07 (106/216) Day6 17.01 (33/194) 18.26 (42/230) 25.53 (24/94) 50.93 (110/216) Expansion degree 0.713 F 0.111 3 15.46 (30/194) 12.61 (29/230) 20.21 (19/94) 21.30 (46/216) 4 51.03 (99/194) 52.61 (121/230) 61.70 (58/94) 50.93 (110/216) 5 32.99 (64/194) 33.48 (77/230) 18.09 (17/94) 24.07 (52/216) 6 0.52 (1/194) 1.30 (3/230) 0.00 (0/94) 3.70 (8/216) P1:P value between G-G and G-P groups; P2 :P value between P-G and P-P groups Table 2 Pregnancy outcomes of frozen-thawed single good- or poor-quality blastocysts with different day 3 embryo quality Blastocyst quality grades Good-quality blastocyst transfers cycles (n=424) Poor-quality blastocyst transfers cycles (n=310) Groups G-G group (n=194) G-P group (n=230) P1 P -G group (n=94) P -P group (n=216) P2 Clinical pregnancy rate 65.98 (128/194) 63.91（147/230） 0.657 58.51 (55/94) 37.96 (82/216) 0.001 Abortion rate 14.06 (18/128) 17.01 (25/147) 0.503 10.91 (6/55) 20.73 (17/82) 0.132 Live birth rate 55.15 (107/194) 53.04 (122/230) 0.664 52.13 (49/94) 28.70 (62/216) < 0.001 P1:P value between G-G and G-P groups; P2 :P value between P-G and P-P groups Table 3 Multivariate logistic regression analysis of the risk factors affecting the clinical pregnancy rate and live birth rate after frozen-thawed single poor-quality blastocyst transfer Predictors Clinical pregnancy rate Live birth rate OR (95% CI) P1 OR (95% CI) P2 Age(year) 0.953 (0.890-1.021) 0.168 0.920 (0.855-0.990) 0.025 BMI(kg/m 2 ) 1.050 (0.974-1.132) 0.207 1.013 (0.939-1.093) 0.736 Duration of infertility(year) 1.049 (0.928-1.186) 0.444 1.093 (0.961-1.242) 0.176 Endometrial thickness(mm) 1.134 (0.991-1.299) 0.068 1.157 (1.005-1.331) 0.042 Infertility type (primary infertility VS. secondary infertility) 0.789 (0.473-1.315) 0.363 0.719 (0.420-1.231) 0.230 Endometrial preparation (natural cycles VS. hormone therapy cycles) 0.781 (0.332-1.834) 0.570 1.013 (0.418-2.458) 0.977 Day 3 embryo quality (good VS. poor) 2.006 (1.185-3.395) 0.010 2.318 (1.355-3.966) 0.002 Blastocyst frozen day (day5 VS. day6) 2.128 (1.271-3.562) 0.004 2.472 (1.418-4.307) 0.001 Expansion degree 4(VS.3) 1.276 (0.681-2.392) 0.446 1.457 (0.756-2.810) 0.261 5(VS.3) 0.952 (0.442-2.050) 0.899 1.125 (0.497-2.547) 0.778 6(VS.3) 2.004 (0.400-10.045) 0.398 2.123 (0.352-12.801) 0.412 P1: P value of the risk factors that affected the clinical pregnancy rate after frozen-thawed single poor-quality blastocyst transfer; P2: P value of the risk factors that affected the live birth rate after frozen-thawed single poor-quality blastocyst transfer Additional Declarations No competing interests reported. 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Children's Medical Center, Guangzhou Medical University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Minna","middleName":"","lastName":"Yin","suffix":""},{"id":295240533,"identity":"947d4536-b802-4044-962d-e58549e93ef4","order_by":2,"name":"Ling Sun","email":"","orcid":"","institution":"Guangzhou Women and Children's Medical Center, Guangzhou Medical University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Ling","middleName":"","lastName":"Sun","suffix":""},{"id":295240534,"identity":"14d8e725-32c5-421b-9e61-5fc550a78da1","order_by":3,"name":"Jian Xu","email":"","orcid":"","institution":"Guangzhou Women and Children's Medical Center, Guangzhou Medical University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Jian","middleName":"","lastName":"Xu","suffix":""},{"id":295240535,"identity":"3fe3d6e1-0b8a-4b29-aa5a-dc8968719717","order_by":4,"name":"Jun Liu","email":"","orcid":"","institution":"Guangzhou Women and Children's Medical Center, Guangzhou Medical University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Jun","middleName":"","lastName":"Liu","suffix":""},{"id":295240536,"identity":"71d1c89b-01f9-442d-9a5a-e7596606da7b","order_by":5,"name":"Hui Wang","email":"","orcid":"","institution":"Guangzhou Women and Children's Medical Center, Guangzhou Medical University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Hui","middleName":"","lastName":"Wang","suffix":""},{"id":295240537,"identity":"24ff6759-29d0-4373-a25c-5323228f1df5","order_by":6,"name":"Yunhao Liang","email":"","orcid":"","institution":"Guangzhou Women and Children's Medical Center, Guangzhou Medical 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Medical Center, Guangzhou Medical University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Meiyi","middleName":"","lastName":"Li","suffix":""},{"id":295240541,"identity":"ab30bace-848d-40de-af75-25727094e271","order_by":10,"name":"Zhufeng Wu","email":"","orcid":"","institution":"Guangzhou Women and Children's Medical Center, Guangzhou Medical University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zhufeng","middleName":"","lastName":"Wu","suffix":""},{"id":295240542,"identity":"fbce28d7-a390-4888-8ed8-d03f8c3c4fc3","order_by":11,"name":"Zhiheng Chen","email":"","orcid":"","institution":"Guangzhou Women and Children's Medical Center, Guangzhou Medical University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zhiheng","middleName":"","lastName":"Chen","suffix":""},{"id":295240543,"identity":"3970f85a-93c8-449f-8dad-5a03c4e35f8a","order_by":12,"name":"Shuai Liu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA1klEQVRIiWNgGAWjYBACPmYGBiBi4OFnZmx8kFBhQ1gLG0yLZHtzs8GDM2lEaGGAaGEw6DneJvmw7RARWth5jD8XttnJGEgktlUksB1g4G/vTiDgMB4z6ZltyTzmQC03EnjuMEicObuBoBZm3jZmHssZIC0SzxgMJHIJajH+zNtWz2NwI7GtIMHgMFFaDKR52w7zGJw52MaQkECUFrYyaZ5zx4GB3NgskXAgjYegX/j5D2/+zFNWbc/PzP7w489/NnL87b34tWAAHtKUj4JRMApGwSjACgBQUEAAJQeDngAAAABJRU5ErkJggg==","orcid":"","institution":"Guangzhou Women and Children's Medical Center, Guangzhou Medical University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Shuai","middleName":"","lastName":"Liu","suffix":""}],"badges":[],"createdAt":"2024-04-23 16:58:29","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4313510/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4313510/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":88665920,"identity":"945a03fd-93c7-45ca-b0ad-440c5b93acb9","added_by":"auto","created_at":"2025-08-09 00:31:21","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1024301,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4313510/v1/360452f4-dae3-4ecc-b4e9-27936d88e66e.pdf"},{"id":55573805,"identity":"1fa32905-ee65-4117-b995-da6caf0525e0","added_by":"auto","created_at":"2024-04-30 06:12:56","extension":"jpg","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":601521,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryFig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4313510/v1/38b5e69c6835cae0f069a30a.jpg"},{"id":55573804,"identity":"f885e026-3bb4-4b9c-9d21-3804909f2b45","added_by":"auto","created_at":"2024-04-30 06:12:56","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":14997,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryFigurelegend.docx","url":"https://assets-eu.researchsquare.com/files/rs-4313510/v1/a90764befe419792e7fd06e7.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Day 3 embryo quality is a predictor for the clinical pregnancy rate and live birth rate in single frozen- thawed poor-quality blastocyst transfer","fulltext":[{"header":"Introduction","content":"\u003cp\u003eIt has been well known that single embryo transfer (SET) is the best\u0026nbsp;method\u0026nbsp;for reducing multiple pregnancy rate, resulting in decreased risks for both maternal and neonatal outcomes in assisted reproductive technology (ART) \u003csup\u003e[1-4]\u003c/sup\u003e. The key of SET is selecting\u0026nbsp;the most viable embryo for transfer to reduce multiple pregnancies while maintaining a high rate of successful pregnancies during in vitro fertilization(IVF) treatment\u003csup\u003e[5,6]\u003c/sup\u003e.\u0026nbsp;Now,\u0026nbsp;the most commonly used method for evaluating embryo development is still static morphological evaluation.\u003c/p\u003e\n\u003cp\u003eThere is evidence that single blastocyst transfer has been shown to yield superior pregnancy outcomes compared to single cleavage-stage embryo\u0026nbsp;transfer \u003csup\u003e[7,8]\u003c/sup\u003e.\u0026nbsp;Blastocyst morphological grading is a\u0026nbsp;useful\u0026nbsp;method for blastocyst selection, however,\u0026nbsp;its predictive value for pregnancy outcomes is still limited \u003csup\u003e[9-\u003c/sup\u003e\u003csup\u003e11]\u003c/sup\u003e.\u0026nbsp;The study examining chromosomal status of good-quality blastocysts still\u0026nbsp;reports\u0026nbsp;overall aneuploidy rates of 39-57%\u0026nbsp;\u003csup\u003e[12]\u003c/sup\u003e.\u0026nbsp;Moreover, it is difficult that\u0026nbsp;determining which one has better developmental potential when\u0026nbsp;multiple same grade blastocysts are obtained.\u0026nbsp;Therefore, having effective methods for blastocyst selection is crucial.\u003c/p\u003e\n\u003cp\u003eDay 3 embryo\u0026nbsp;quality is\u0026nbsp;an important evaluation parameter for cleavage stage embryo selection,\u0026nbsp;is it still an important parameter for blastocyst selection?\u0026nbsp;Xia\u0026nbsp;et al \u003csup\u003e[13]\u0026nbsp;\u003c/sup\u003eindicated that day 3 poor-quality embryos may have a negative impact on the pregnancy\u0026nbsp;outcomes, but it is not clear whether these\u0026nbsp;differences still exist when different quality embryo at day 3 are cultured to same morphological grade blastocysts.\u0026nbsp;Several studies\u0026nbsp;showed that there was controversy regarding the effects of day 3 embryo quality on pregnancy outcomes after single good-quality blastocyst transfer\u003csup\u003e[14-19]\u003c/sup\u003e. Moreover,\u0026nbsp;as we known,\u0026nbsp;to date,\u0026nbsp;only\u0026nbsp;two studies\u0026nbsp;have\u0026nbsp;analyzed the relationship between day 3 embryo quality and pregnancy outcomes in single poor-quality blastocyst transfer cycles\u0026nbsp;\u003csup\u003e[17,18]\u003c/sup\u003e.\u0026nbsp;And their\u0026nbsp;results showed that there was no relationship between them.\u0026nbsp;Despite these results, it is still unclear whether and how we should focus attention on day 3 embryo quality when transferring single particular grade frozen- warmed blastocysts, especially poor-quality blastocysts .\u003c/p\u003e\n\u003cp\u003eTherefore, the purpose of our study is to investigate correlation between day 3 embryo quality and the pregnancy outcomes after single good- or poor-quality frozen-thawed blastocyst transfer. It will help us to know the role of day 3 embryo quality in the same grade blastocyst selection.\u003c/p\u003e"},{"header":"Materials And Methods","content":"\u003cp\u003e\u003cstrong\u003ePatients\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA retrospective analysis was performed\u0026nbsp;between\u0026nbsp;January 2018 to October 2021 at the Centre for Reproductive Medicine of Guangzhou Women and Children\u0026rsquo;s Medical Center. Patients undergoing frozen embryo transfer (FET) cycles with single blastocyst transfer were included. The cycle exclusion criteria are as follows: (1) cycles involving preimplantation genetic testing (PGT); (2) cycles involving female aged over 40 years; (3) cycles involving congenital uterine malformations or endometrium \u0026lt;7mm; (4) cycles involving day 7 blastocyst transfer;(5) cycles involving blastocyst accessed as less than 3BC/3CB.The participant selection process is detailed in Fig. 1. Finally, 734 single frozen-thawed blastocyst transfer cycles were analyzed. These cycles were categorized into\u0026nbsp;four groups\u0026nbsp;according to embryo grade:\u0026nbsp;the good-quality blastocysts derived from day 3 good-quality embryos group (G-G group, n=194), the good-quality blastocysts derived from day 3 poor-quality embryos group (G-P group, n=230), the poor-quality blastocysts derived from day 3 good-quality embryos group (P-G group, n=94) and the poor-quality blastocysts derived from day 3 poor-quality embryos group (P-P group, n=216).\u0026nbsp;The primary outcome of the study was the live birth rate (LBR), while the secondary\u0026nbsp;outcomes included\u0026nbsp;clinical pregnancy rate (CPR), miscarriage rate.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCleavage stage embryos and blastocyst scoring\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConventional IVF and intracytoplasmic sperm injection (ICSI) procedures were conducted 3-6 hours after oocyte retrieval, followed by a fertilization check at 16-18 hours post-insemination. A zygote with two pronuclei (2PN) and were cultured in G1\u003csup\u003eTM\u003c/sup\u003e (Vitrolife, Sweden) under mineral oil. Embryos that underwent extended culture were transferred to G2\u003csup\u003eTM\u003c/sup\u003e (Vitrolife, Sweden) on day 3 and cultured until day 5 or 6 under mineral oil. All cultures took place in incubators set at a temperature of 37\u0026deg;C with 6% CO2, 5% O2 and 89% N2. Day 3 embryos were assessed according to the Istanbul consensus \u003csup\u003e[20]\u003c/sup\u003e. Blastocysts were assessed according to Gardner and Schoolcraft\u0026apos;s classification. In our laboratory, day 3 good-quality embryos are characterized by having 7-8 cells on day 3, less than 10% fragmentation, symmetrical blastomeres, and an absence of multinucleation. A good-quality blastocyst was defined as blastocysts of grade 3BB or higher.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eBlastocyst vitrification and thawing procedures\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe criterion for cryopreservation and transfer of blastocysts in our study was a blastocyst grade of at least 3BC/3CB. Vitrification was employed for cryopreservation, and the embryos were thawed using a standardized procedure (Jieying thawing medium, Jieying Laboratory Inc., Canada).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEmbryo transfer and pregnancy\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCryopreserved blastocyst transfers were scheduled during either a natural or exogenous steroid replacement cycle, with warmed blastocysts cultured for 2 hours before transfer. Serum HCG levels were assessed 12 days after blastocyst transfer, and clinical pregnancy was defined as the presence of a gestational sac exhibiting fetal heart activity detected via vaginal ultrasound at 7 weeks\u0026apos; gestation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe statistical analysis was conducted using SPSS 22.0 software. For quantitative data with a normal distribution, Student\u0026apos;s t-test was applied, while the Mann-Whitney U test was utilized for quantitative data with an abnormal distribution. Qualitative data underwent testing using the chi-squared test or Fisher\u0026apos;s exact test when appropriate. Additionally, a multivariate logistic regression analysis was performed to identify confounding factors independently related to the LBR and CPR. The odds ratio (OR) with 95% confidence intervals (CIs) was calculated. A P value \u0026lt; 0.05 was considered statistically significant.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eThe inclusion process of patients is detailed in Fig. 1. From the initial cohort of 1188 single frozen-thewed blastocyst transfer\u0026nbsp;cycles conducted in our reproductive center during the study period, 454 single frozen-thewed blastocyst transfer\u0026nbsp;cycles were excluded for various reasons: PGT cycles (n=364), female age over 40 years (n=41), and cycles with day 7 blastocysts, uterine malformations, or endometrium less than 7mm (n=49). Consequently, a total of 734 single frozen-thewed blastocyst transfer cycles were included.\u0026nbsp;Within this cohort, patients\u0026nbsp;were divided into\u0026nbsp;four\u0026nbsp;groups: G-G group(n=194), G-P group(n=230), P-G group(n=94) and P-P group (n=216).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePatient and embryo characteristics of\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003efrozen-thawed\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003esingle\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003egood- or poor-quality\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eblastocysts with different day 3\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eembryo quality\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAs shown in Table 1, no significant differences were observed in female\u0026nbsp;age, female\u0026nbsp;body mass index (BMI), infertility duration, endometrial thickness, infertility types, endometrial preparation, blastocyst frozen day (day 5/6) and degree of expansion (B3/4/5/6) between G-G and G-P groups(P\u0026ge;0.05).\u0026nbsp;Additional, patient and embryo characteristics were comparable between P-G and P-P groups, except\u0026nbsp;the proportion of vitrified day 5 blastocysts of P-G group was higher than P-P group (74.47% vs. 49.07%, P\u0026lt;0.001).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePregnancy outcomes of\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003efrozen-thawed\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003esingle\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003egood- or poor-quality\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eblastocysts with different day 3\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eembryo quality\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn Table 2,\u0026nbsp;the CPR (65.98% vs. 63.91%, P\u0026ge;0.05), abortion rate (14.06% vs. 17.01%, P\u0026ge;0.05) and LBR (55.15% vs. 53.04%, P\u0026ge;0.05) did no differ significantly between G-G and G-P groups. The\u0026nbsp;abortion rates were similar between P-G and P-P groups (10.91% vs. 20.73%, P\u0026ge;0.05), however, the CPR (58.51% vs. 37.96%, P\u0026lt;0.01) and LBR (52.13% vs. 28.70%, P\u0026lt;0.001) of the P-G group were significantly higher than those of the P-P group.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eThe clinical outcomes of the four groups were compared in pairs\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn\u0026nbsp;Supplementary Fig1,\u0026nbsp;the\u0026nbsp;CPR\u0026nbsp;and\u0026nbsp;LBR\u0026nbsp;of\u0026nbsp;four\u0026nbsp;groups were compared in pairs. The results revealed that the\u0026nbsp;CPR\u0026nbsp;and\u0026nbsp;LBR\u0026nbsp;of the P-P group were significantly lower than those of G-G, G-P, and P-G groups (P\u0026lt;0.01, respectively). However, there were no significant differences in the\u0026nbsp;CPR\u0026nbsp;and\u0026nbsp;LBR\u0026nbsp;among G-G, G-P and P-G groups (P\u0026ge;0.05, respectively).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMultivariate\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003elogistic regression analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMultivariate logistic regression analysis was conducted to examine the variables influencing CPR and LBR of single frozen-thewed poor-quality blastocyst transfer cycles. As presented in Table 3, both day 3 good-quality embryo (OR=2.006 [1.185-3.395], P\u0026lt;0.05) and blastocyst frozen on day 5 (OR=2.128 [1.271-3.562], P\u0026lt;0.01) had a significant positive impact on CPR. Furthermore, age (OR=0.920 [0.855-0.990], P\u0026lt;0.05), endometrial thickness (OR=1.157 [1.005-1.331], P\u0026lt;0.05), day 3 embryo quality (OR=2.318 [1.355-3.966], P\u0026lt;0.01), and blastocyst frozen day (OR=2.472 [1.418-4.307], P\u0026lt;0.01) were found to be significantly associated with LBR. However, the effects of other factors on CPR and LBR did not exhibit significant differences (P\u0026ge;0.05).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eOur finding showed that transferring the single\u0026nbsp;frozen-thewed\u0026nbsp;poor-quality blastocysts derived from day 3 good-quality embryos resulted in higher\u0026nbsp;CPR\u0026nbsp;and\u0026nbsp;LBR\u0026nbsp;compared to those derived from day 3 poor-quality embryos and achieved similar CPR and LBR as the good-quality blastocysts derived from day 3 good- and poor- quality embryos.\u003c/p\u003e\n\u003cp\u003ePrevious studies invested that the development potential of good-quality blastocysts from poor-quality cleavage embryos. Kaartinen et al. \u003csup\u003e[21]\u003c/sup\u003e showed that the CPR of vitrified\u0026ndash;warmed good-quality blastocysts derived from poor-quality cleavage embryos was 24.6%, whereas the CPR of vitrified\u0026ndash;warmed good-quality cleavage embryos was 29.4%. Sallem et al\u003csup\u003e[22]\u003c/sup\u003e reported that CPR was 40.8% after extended culture of embryos with poor developmental potential into good-quality blastocyst. In our study, the transfer of good-quality blastocysts from the extended culture of day 3 poor-quality embryos resulted in CPR of 63.91%. These results indicated that the extended culture of poor-quality cleavage embryos can still develop to the blastocyst stage and result in good pregnancy outcomes. This could be explained by embryo plasticity, the proportion of chromosomally abnormal cells varies during the culture, and the corrupted cells can be eliminated resulting in good-quality blastocysts developing from poor-quality cleavage embryos \u003csup\u003e[23]\u003c/sup\u003e. However,\u0026nbsp;it is not clear\u0026nbsp;whether they have comparable pregnancy outcomes to good-quality cleavage embryos when cultured to the good-quality blastocysts. Therefore, in the present study, we compared the pregnancy outcomes between\u0026nbsp;them.\u0026nbsp;The results showed the CPR, LBR and abortion rate are not influenced by good or poor quality at day 3 when good-quality blastocysts are transferred.\u0026nbsp;The conclusion is in line with previous studies\u003csup\u003e[14-16]\u003c/sup\u003e. The study indicated that day 3 embryo quality was not a useful predictor for the pregnancy outcomes in single frozen- thawed good-quality blastocysts.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAs we known, to date, only two studies have analyzed the relationship between day 3 embryo quality and pregnancy outcomes in poor-quality blastocyst transfer cycles \u003csup\u003e[18,19]\u003c/sup\u003e. Shen et al \u003csup\u003e[18]\u003c/sup\u003e found that the day 3 embryo grade (I-II, III-IV) did not influence the CPR and LBR in either BC or CB groups after adjusting for confounding factors. Qiu et al\u003csup\u003e[19]\u003c/sup\u003eshowed that the LBR and miscarriage rate of poor-quality blastocyst from day 3 high-grade embryos were similar with those from day 3 poor-grade embryos(LBR:26.1% VS.28.0%;miscarriage rate:6.6% VS.8.3%).In our study, the CPR and LBR of good-quality blastocysts from day 3 good-quality embryos were significantly higher than those from poor-quality embryos, and achieved similar CPR and LBR as the good-quality blastocysts derived from day 3 good- and poor- quality embryos. These discrepancies between our findings and theirs could be attributed, in part, to a different definition of day 3 good-quality embryos. Moreover, the conventional microscopic assessment of embryo morphology still remains inherently subjective, frequently demonstrating significant variability between different observers and even within the same observer \u003csup\u003e[24-26]\u003c/sup\u003e, thus posing a limitation in this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLimitations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study is subject to several limitations. Firstly, its retrospective design introduces the potential for residual confounding, as inherent biases may not have been completely addressed. Further validation through prospective studies is necessary to strengthen the reliability of our findings. Secondly, the subjective nature of morphological evaluation constrains the objectivity of our findings. Therefore, efforts to standardize evaluation protocols or incorporate more objective measures may enhance the robustness of future studies in this area.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIn conclusion, our study suggests that day 3 embryo quality is not a useful predictor for the pregnancy outcomes in single frozen-thawed good-quality blastocysts. However, day 3 embryo quality is a strong predictor for the clinical pregnancy rate and live birth rate in single frozen-thawed poor-quality blastocysts. This finding is particularly crucial for patients who only produce poor-quality blastocysts, as it optimizes blastocyst freezing and transfer sequencing, ultimately reducing patients\u0026apos; waiting time to achieve successful live births.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eSET:\u0026nbsp;single embryo transfer;\u003c/p\u003e\n\u003cp\u003eART: assisted reproductive technology;\u003c/p\u003e\n\u003cp\u003eIVF: In vitro fertilization;\u003c/p\u003e\n\u003cp\u003eICSI: Intracytoplasmic sperm injection;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFET: frozen embryo transfer;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ePGT: Preimplantation genetic testing;\u003c/p\u003e\n\u003cp\u003eCPR: Clinical pregnancy rate;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eLBR: Live birth rate;\u003c/p\u003e\n\u003cp\u003eBMI: body mass index;\u003c/p\u003e\n\u003cp\u003e2PN: Two pronuclei;\u003c/p\u003e\n\u003cp\u003eHCG: Human Chorionic Gonadotrophin;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eOR: Odds Ratio;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCI: Confidence interval.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMy colleagues for their invaluable input and for being a great source of support to me during this study.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eShuai Liu, Li Yang contributed to the conception and design of the study. Ling Sun, Minna Yin, Jian Xu and Jun Liu contributed to data interpretation. Wang Hui, Yunhao Liang, Huijiao Wu contributed to data analysis. Yu Jiang, Meiyi Li, and Zhu feng Wu contributed to data acquisition. Li Yang and Minna Yin drafted the first version of the manuscript. Shuai Liu and Zhiheng Chen wrote the final version. The authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was funded by Guangzhou Health and Technology Project (20221A011036).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets during the current study are available from the corresponding- g author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study received approval from the Independent Ethics Committee of Guangzhou Women and Children\u0026rsquo;s Hospital (No.001A01).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMcLernon DJ, Harrild K, Bergh C, Davies MJ, de Neubourg D, Dumoulin JC,et al. Clinical effectiveness of elective single versus double embryo transfer: meta-analysis of individual patient data from randomised trials. BMJ. 2010;341:c6945. \u003c/li\u003e\n\u003cli\u003eKamath MS, Mascarenhas M, Kirubakaran R, Bhattacharya S.Number of embryos for transfer following in vitro fertilisation or intra-cytoplasmic sperm injection. Cochrane Database Syst Rev.2020;8:CD003416\u003c/li\u003e\n\u003cli\u003eReimundo P, Guti\u0026eacute;rrez Romero JM, Rodr\u0026iacute;guez P\u0026eacute;rez T, Veiga E. Single-embryo transfer: a key strategy to reduce the risk for multiple pregnancy in assisted human reproduction. Adv Lab Med. 2021;2(2):179-198. \u003c/li\u003e\n\u003cli\u003eWang Y, Shi H, Chen L, Zheng D, Long X, Zhang Y, et al. Absolute Risk of Adverse Obstetric Outcomes Among Twin Pregnancies After In Vitro Fertilization by Maternal Age. JAMA Netw Open. 2021 Sep 1;4(9): e2123634.\u003c/li\u003e\n\u003cli\u003eStimpfel M, Bacer-Kermavner L, Fevzer T, Petric P, Jancar N, Vratcnik-Bokal E. P\u0026ndash;780 The increase of single embryo transfers does not impair pregnancy and live birth rates, although it lowers twin rate . Hum Reprod. 2021-08-06; 36 (Supple1).\u003c/li\u003e\n\u003cli\u003eUbaldi FM, Capalbo A, Colamaria S, Ferrero S, Maggiulli R, Vajta G, et al. Reduction of multiple pregnancies in the advanced maternal age population after implementation of an elective single embryo transfer policy coupled with enhanced embryo selection: pre- and post-intervention study. Hum Reprod. 2015; 30 (9): 2097-106.\u003c/li\u003e\n\u003cli\u003eLi Y, Liu S, Lv Q. Single blastocyst stage versus single cleavage stage embryo transfer following fresh transfer: A systematic review and meta-analysis. Eur J Obstet Gynecol Reprod Biol. 2021; 26711-17. \u003c/li\u003e\n\u003cli\u003eGlujovsky D, Quinteiro Retamar AM, Alvarez Sedo CR, Ciapponi A, Cornelisse S, Blake D. Cleavage-stage versus blastocyst-stage embryo transfer in assisted reproductive technology. Cochrane Database Syst Rev. 2022;5(5):CD002118.\u003c/li\u003e\n\u003cli\u003eKim MK, Park JK, Jeon Y, Choe SA, Lee HJ, Kim J, et al. Correlation between Morphologic Grading and Euploidy Rates of Blastocysts, and Clinical Outcomes in In Vitro Fertilization Preimplantation Genetic Screening. J Korean Med Sci. 2019; 34(4): e27.\u003c/li\u003e\n\u003cli\u003eIrani M, Reichman D, Robles A, Melnick A, Davis O, Zaninovic N, et al. Morphologic grading of euploid blastocysts influences implantation and ongoing pregnancy rates.Fertil Steril. 2017;107(3):664\u0026ndash;670.\u003c/li\u003e\n\u003cli\u003eZou H, Kemper JM, Hammond ER, Xu F, Liu G, Xue L, et al. Blastocyst quality and reproductive and perinatal outcomes: a multinational multicentre observational study. Hum Reprod. 2023; 38 (12): 2391-99. \u003c/li\u003e\n\u003cli\u003eFragouli E, Katz-Jaffe M, Alfarawati S, Stevens J, Colls P, Goodall NN, et al. Comprehensive chromosome screening of polar bodies and blastocysts from couples experiencing repeated implantation failure. Fertil Steril. 2010;94(3):875-87.\u003c/li\u003e\n\u003cli\u003eXia L, Zhao S, Xu H, Wu X, Zhang A, Niu Z. Miscarriage Rate Is High With Frozen-Thawed Blastocysts Arising From Poor-Quality Cleavage Stage Embryos. Front Endocrinol (Lausanne). 2020;11: 561085. \u003c/li\u003e\n\u003cli\u003eGuerif F, Lemseffer M, Leger J, Bidault R, Cadoret V, Chavez C, et al. Does early morphology provide additional selection power to blastocyst selection for transfer? Reprod Biomed Online. 2010 ;21(4):510-9.\u003c/li\u003e\n\u003cli\u003eRehman KS, Bukulmez O, Langley M, Carr BR, Nackley AC, Doody KM, et al. Late stages of embryo progression are a much better predictor of clinical pregnancy than early cleavage in intracytoplasmic sperm injection and in vitro fertilization cycles with blastocyst-stage transfer. Fertil Steril. 2007 ;87(5):1041-52. \u003c/li\u003e\n\u003cli\u003eHerbemont C, Sarandi S, Boujenah J, Cedrin-Durnerin I, Sermondade N, Vivot A, et al. Should we consider day-2 and day-3 embryo morphology before day-5 transfer when blastocysts reach a similar good quality? Reprod Biomed Online. 2017;35(5):521-528.\u003c/li\u003e\n\u003cli\u003eSilber, S., 2014. Blastocysts that came from better quality day 3 embryos give higher pregnancy rates than blastocysts that derive from poor quality day 3 embryos. Ovarian Club, Paris.\u003c/li\u003e\n\u003cli\u003eShen X, Long H, Gao H, Guo W, Xie Y, Chen D, et al. The Valuable Reference of Live Birth Rate in the Single Vitrified-Warmed BB/BC/CB Blastocyst Transfer: The Cleavage-Stage Embryo Quality and Embryo Development Speed. Front Physiol. 2020; 11:1102. \u003c/li\u003e\n\u003cli\u003eQiu J, Du T, Guo H, Mol BW, Lin J, Zhao D, et al. Does Day 3 embryo status matter to reproductive outcomes of single blastocyst transfer cycles? A cohort study. BJOG. 2023 Dec;130(13):1669-1676. \u003c/li\u003e\n\u003cli\u003eAlpha Scientists in Reproductive Medicine and ESHRE Special Interest Group of Embryology. The Istanbul consensus workshop on embryo assessment: proceedings of an expert meeting. Hum Reprod. 2011;26(6):1270-83.\u003c/li\u003e\n\u003cli\u003eKaartinen N, Das P, Kananen K, Huhtala H, Tinkanen H. Can repeated IVF-ICSI-cycles be avoided by using blastocysts developing from poor-quality cleavage stage embryos? Reprod Biomed Online. 2015 ;30(3):241-7. \u003c/li\u003e\n\u003cli\u003eSallem A, Santulli P, Barraud-Lange V, Le Foll N, Ferreux L, Maignien C, et al. Extended culture of poor-quality supernumerary embryos improves ART outcomes. J Assist Reprod Genet. 2018 ;35(2):311-319. \u003c/li\u003e\n\u003cli\u003eFragouli E, Alfarawati S, Spath K, Jaroudi S, Sarasa J, Enciso M, et al. The origin and impact of embryonic aneuploidy. Hum Genet. 2013; 132 (9): 1001-13.\u003c/li\u003e\n\u003cli\u003ePaternot G, Wetzels AM, Thonon F, Vansteenbrugge A, Willemen D, Devroe J, et al. Intra- and interobserver analysis in the morphological assessment of early stage embryos during an IVF procedure: a multicentre study. Reprod Biol Endocrinol. 2011; 9:127.\u003c/li\u003e\n\u003cli\u003eHammond ER, Foong AKM, Rosli N, Morbeck DE. Should we freeze it? Agreement on fate of borderline blastocysts is poor and does not improve with a modified blastocyst grading system. Hum Reprod. 2020 ;35(5):1045-1053. \u003c/li\u003e\n\u003cli\u003eChiappetta V, Innocenti F, Coticchio G, Ahlstr\u0026ouml;m A, Albricci L, Badajoz V,et al . Discard or not discard, that is the question: an international survey across 117 embryologists on the clinical management of borderline quality blastocysts. Hum Reprod. 2023 ;38(10):1901-1909. \u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e Patient and embryo characteristics of frozen-thawed single good- or poor-quality blastocysts with different day 3 embryo quality\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"748\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.06417112299465%\"\u003e\n \u003cp\u003e\u003cstrong\u003eBlastocyst quality grades\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"36.63101604278075%\" colspan=\"3\"\u003e\n \u003cp\u003e\u003cstrong\u003eGood-quality\u0026nbsp;blastocyst transfers cycles\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=424)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"39.3048128342246%\" colspan=\"3\"\u003e\n \u003cp\u003e\u003cstrong\u003ePoor-quality blastocyst transfers cycles\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=310)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroups\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e\u003cstrong\u003eG-G group\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=194)\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e\u003cstrong\u003eG-P group\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=230)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e\u003cstrong\u003eP1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e\u003cstrong\u003eP-G group\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=94)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;P\u003c/strong\u003e\u003cstrong\u003e-P group\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=216)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e\u003cstrong\u003eP2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003eCycles\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e194\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e230\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e216\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003eFemale\u0026nbsp;Age(year)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e31.42\u0026plusmn;3.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e31.50\u0026plusmn;3.42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e0.826\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e31.80\u0026plusmn;3.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e32.11\u0026plusmn;3.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e0.489\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003eFemale\u0026nbsp;BMI(kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e20.93\u0026plusmn;3.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e21.46\u0026plusmn;2.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e21.24\u0026plusmn;3.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e20.96\u0026plusmn;3.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e0.481\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003eDuration of\u0026nbsp;infertility(year)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e2.55 (1.00,4.00)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e2.00 (1.00,3.00)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e0.097\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e2.00 (1.20,3.25)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e2.00 (1.20,3.00)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e0.754\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003eEndometrial thickness(mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e9.73\u0026plusmn;1.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e9.76\u0026plusmn;1.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e0.876\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e9.68\u0026plusmn;1.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e9.88\u0026plusmn;1.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e0.377\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003eInfertility type\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e0.409\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e0.749\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003ePrimary infertility\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e43.81 (85/194)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e47.83 (110/230)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e43.62 (41/94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e41.67 (90/216)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003eSecondary infertility\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e56.19 (109/194)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e52.17 (120/230)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e56.38 (53/94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e58.33 (126/216)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003eEndometrial preparation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e0.289\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e0.165\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003eNatural cycles\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e10.31 (20/194)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e7.39 (17/230)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e11.70 (11/94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e6.94 (15/216)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003eHormone therapy cycles\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e89.69 (174/194)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e92.61 (213/230)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e88.30 (83/94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e93.06 (199/216)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003eBlastocyst frozen day\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e0.737\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e\u0026lt; 0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003eDay5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e82.99 (161/194)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e81.74 (188/230)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e74.47 (70/94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e49.07 (106/216)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003eDay6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e17.01 (33/194)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e18.26 (42/230)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e25.53 (24/94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e50.93 (110/216)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003eExpansion degree\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e0.713\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e0.111\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e15.46 (30/194)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e12.61 (29/230)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e20.21 (19/94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e21.30 (46/216)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e51.03 (99/194)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e52.61 (121/230)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e61.70 (58/94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e50.93 (110/216)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e32.99 (64/194)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e33.48 (77/230)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e18.09 (17/94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e24.07 (52/216)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"24.096385542168676%\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e0.52 (1/194)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.127175368139223%\"\u003e\n \u003cp\u003e1.30 (3/230)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"6.291834002677376%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.599732262382865%\"\u003e\n \u003cp\u003e0.00 (0/94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.056224899598394%\"\u003e\n \u003cp\u003e3.70 (8/216)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.701472556894243%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eP1:P value between G-G and G-P groups; P2 :P value between P-G and P-P groups\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2\u003c/strong\u003e Pregnancy outcomes of frozen-thawed single good- or poor-quality blastocysts with different day 3 embryo quality\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"721\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"20.943134535367545%\"\u003e\n \u003cp\u003e\u003cstrong\u003eBlastocyst quality grades\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"40.221914008321775%\" colspan=\"4\"\u003e\n \u003cp\u003e\u003cstrong\u003eGood-quality\u0026nbsp;blastocyst transfers cycles\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=424)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"38.83495145631068%\" colspan=\"5\"\u003e\n \u003cp\u003e\u003cstrong\u003ePoor-quality blastocyst transfers cycles\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=310)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20.943134535367545%\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroups\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.672676837725382%\"\u003e\n \u003cp\u003e\u003cstrong\u003eG-G group\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=194)\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.475728155339805%\" colspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003eG-P\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003egroup\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=230)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.0735090152565885%\"\u003e\n \u003cp\u003e\u003cstrong\u003eP1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.701803051317615%\" colspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;P\u003c/strong\u003e\u003cstrong\u003e-G\u003c/strong\u003e\u003cstrong\u003egroup\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=94)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.979195561719834%\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;P\u003c/strong\u003e\u003cstrong\u003e-P group\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n=216)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.153952843273231%\" colspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003eP2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20.97222222222222%\"\u003e\n \u003cp\u003eClinical pregnancy rate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.694444444444445%\"\u003e\n \u003cp\u003e65.98 (128/194)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.083333333333332%\"\u003e\n \u003cp\u003e63.91（147/230）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.5%\" colspan=\"2\"\u003e\n \u003cp\u003e0.657\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003e58.51 (55/94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.694444444444445%\" colspan=\"3\"\u003e\n \u003cp\u003e37.96 (82/216)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.472222222222221%\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20.97222222222222%\"\u003e\n \u003cp\u003eAbortion rate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.694444444444445%\"\u003e\n \u003cp\u003e14.06 (18/128)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.083333333333332%\"\u003e\n \u003cp\u003e17.01 (25/147)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.5%\" colspan=\"2\"\u003e\n \u003cp\u003e0.503\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003e10.91 (6/55)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.694444444444445%\" colspan=\"3\"\u003e\n \u003cp\u003e20.73 (17/82)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.472222222222221%\"\u003e\n \u003cp\u003e0.132\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20.97222222222222%\"\u003e\n \u003cp\u003eLive birth rate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.694444444444445%\"\u003e\n \u003cp\u003e55.15 (107/194)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.083333333333332%\"\u003e\n \u003cp\u003e53.04 (122/230)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"7.5%\" colspan=\"2\"\u003e\n \u003cp\u003e0.664\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.583333333333334%\"\u003e\n \u003cp\u003e52.13 (49/94)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.694444444444445%\" colspan=\"3\"\u003e\n \u003cp\u003e28.70 (62/216)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.472222222222221%\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt; 0.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eP1:P value between G-G and G-P groups; P2 :P value between P-G and P-P groups\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3 \u003c/strong\u003eMultivariate logistic regression analysis of the risk factors affecting the clinical pregnancy rate and live birth rate after frozen-thawed single poor-quality blastocyst transfer\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"643\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"36.70295489891135%\" rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003ePredictors\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.34836702954899%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eClinical pregnancy\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003erate\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"30.948678071539657%\" colspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eLive birth rate\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"37.34643734643735%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eOR (95% CI)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.75921375921376%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eP1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"35.62653562653563%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eOR (95% CI)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.267813267813267%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eP2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"36.70295489891135%\"\u003e\n \u003cp\u003eAge(year)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.63919129082426%\" valign=\"top\"\u003e\n \u003cp\u003e0.953 (0.890-1.021)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.709175738724728%\" valign=\"top\"\u003e\n \u003cp\u003e0.168\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.55054432348367%\" valign=\"top\"\u003e\n \u003cp\u003e0.920 (0.855-0.990)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.398133748055988%\" valign=\"top\"\u003e\n \u003cp\u003e0.025\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"36.70295489891135%\"\u003e\n \u003cp\u003eBMI(kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.63919129082426%\" valign=\"top\"\u003e\n \u003cp\u003e1.050 (0.974-1.132)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.709175738724728%\" valign=\"top\"\u003e\n \u003cp\u003e0.207\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.55054432348367%\" valign=\"top\"\u003e\n \u003cp\u003e1.013 (0.939-1.093)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.398133748055988%\" valign=\"top\"\u003e\n \u003cp\u003e0.736\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"36.70295489891135%\"\u003e\n \u003cp\u003eDuration of infertility(year)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.63919129082426%\" valign=\"top\"\u003e\n \u003cp\u003e1.049 (0.928-1.186)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.709175738724728%\" valign=\"top\"\u003e\n \u003cp\u003e0.444\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.55054432348367%\" valign=\"top\"\u003e\n \u003cp\u003e1.093 (0.961-1.242)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.398133748055988%\" valign=\"top\"\u003e\n \u003cp\u003e0.176\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"36.70295489891135%\"\u003e\n \u003cp\u003eEndometrial thickness(mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.63919129082426%\" valign=\"top\"\u003e\n \u003cp\u003e1.134 (0.991-1.299)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.709175738724728%\" valign=\"top\"\u003e\n \u003cp\u003e0.068\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.55054432348367%\" valign=\"top\"\u003e\n \u003cp\u003e1.157 (1.005-1.331)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.398133748055988%\" valign=\"top\"\u003e\n \u003cp\u003e0.042\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"36.70295489891135%\"\u003e\n \u003cp\u003eInfertility type (primary infertility VS. secondary infertility)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.63919129082426%\" valign=\"top\"\u003e\n \u003cp\u003e0.789 (0.473-1.315)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.709175738724728%\" valign=\"top\"\u003e\n \u003cp\u003e0.363\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.55054432348367%\" valign=\"top\"\u003e\n \u003cp\u003e0.719 (0.420-1.231)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.398133748055988%\" valign=\"top\"\u003e\n \u003cp\u003e0.230\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"36.70295489891135%\"\u003e\n \u003cp\u003eEndometrial preparation (natural cycles VS. hormone therapy cycles)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.63919129082426%\" valign=\"top\"\u003e\n \u003cp\u003e0.781 (0.332-1.834)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.709175738724728%\" valign=\"top\"\u003e\n \u003cp\u003e0.570\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.55054432348367%\" valign=\"top\"\u003e\n \u003cp\u003e1.013 (0.418-2.458)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.398133748055988%\" valign=\"top\"\u003e\n \u003cp\u003e0.977\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"36.70295489891135%\"\u003e\n \u003cp\u003eDay 3 embryo quality (good VS. poor)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.63919129082426%\" valign=\"top\"\u003e\n \u003cp\u003e2.006 (1.185-3.395)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.709175738724728%\" valign=\"top\"\u003e\n \u003cp\u003e0.010\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.55054432348367%\" valign=\"top\"\u003e\n \u003cp\u003e2.318 (1.355-3.966)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.398133748055988%\" valign=\"top\"\u003e\n \u003cp\u003e0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"36.70295489891135%\"\u003e\n \u003cp\u003eBlastocyst frozen day (day5 VS. day6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.63919129082426%\" valign=\"top\"\u003e\n \u003cp\u003e2.128 (1.271-3.562)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.709175738724728%\" valign=\"top\"\u003e\n \u003cp\u003e0.004\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.55054432348367%\" valign=\"top\"\u003e\n \u003cp\u003e2.472 (1.418-4.307)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.398133748055988%\" valign=\"top\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"36.70295489891135%\"\u003e\n \u003cp\u003eExpansion degree\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.63919129082426%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.709175738724728%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.55054432348367%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.398133748055988%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"36.70295489891135%\"\u003e\n \u003cp\u003e4(VS.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.63919129082426%\" valign=\"top\"\u003e\n \u003cp\u003e1.276 (0.681-2.392)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.709175738724728%\" valign=\"top\"\u003e\n \u003cp\u003e0.446\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.55054432348367%\" valign=\"top\"\u003e\n \u003cp\u003e1.457 (0.756-2.810)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.398133748055988%\" valign=\"top\"\u003e\n \u003cp\u003e0.261\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"36.70295489891135%\"\u003e\n \u003cp\u003e5(VS.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.63919129082426%\" valign=\"top\"\u003e\n \u003cp\u003e0.952 (0.442-2.050)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.709175738724728%\" valign=\"top\"\u003e\n \u003cp\u003e0.899\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.55054432348367%\" valign=\"top\"\u003e\n \u003cp\u003e1.125 (0.497-2.547)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.398133748055988%\" valign=\"top\"\u003e\n \u003cp\u003e0.778\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"36.70295489891135%\"\u003e\n \u003cp\u003e6(VS.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"23.63919129082426%\" valign=\"top\"\u003e\n \u003cp\u003e2.004 (0.400-10.045)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.709175738724728%\" valign=\"top\"\u003e\n \u003cp\u003e0.398\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.55054432348367%\" valign=\"top\"\u003e\n \u003cp\u003e2.123 (0.352-12.801)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.398133748055988%\" valign=\"top\"\u003e\n \u003cp\u003e0.412\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eP1: P value of the risk factors that affected the clinical pregnancy rate after frozen-thawed single poor-quality blastocyst transfer; P2: P value of the risk factors that affected the live birth rate after frozen-thawed single poor-quality blastocyst transfer\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Single blastocyst transfer, Day 3 embryo quality, Live birth rate, Clinical pregnancy rate","lastPublishedDoi":"10.21203/rs.3.rs-4313510/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4313510/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eObjective: \u003c/strong\u003eThis study aimed to investigate the utility of day 3 embryo quality in the selection of same-grade blastocysts, particularly focusing on poor-quality blastocysts, to predict clinical pregnancy and live birth rates.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods: \u003c/strong\u003eSeven hundred and thirty-four frozen-thawed single blastocyst transfer cycles carried out between January 2018 to October 2021 were retrospectively analyzed. Cycles were categorized into four groups based on embryo grade: G-G group (good-quality blastocysts derived from day 3 good-quality embryos group, n=194), G-P group (good-quality blastocysts derived from day 3 poor-quality embryos group, n=230), P-Ggroup (poor-quality blastocysts derived from day 3 good-quality embryos group, n=94) and P-P group (poor-quality blastocysts derived from day 3 poor-quality embryos group, n=216). The analysis focused on the role of the day 3 embryo quality in selecting single frozen-thawed good- or poor- quality blastocyst for transfer.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e Good-quality blastocysts derived from day 3 poor-quality embryos had comparable pregnancy outcomes to those derived from day 3 good-quality embryos (clinical pregnancy rates: 63.91% vs. 65.98%; live birth rates: 53.04% vs. 55.15%, respectively P≥0.05). However, poor-quality blastocysts derived from day 3 good-quality embryos exhibited significantly higher clinical pregnancy rates (58.51% vs. 37.96%, P＜0.01; OR 2.006,95% CI 1.185-3.395, P＜0.05) and live birth rates (52.13% vs. 28.70%, P＜0.001; OR 2.318, 95% CI 1.355-3.966, P＜0.01) than those derived from day 3 poor-quality embryos.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion(s):\u003c/strong\u003e Day 3 embryo quality serves as a predictor for the clinical pregnancy and live birth rate after single frozen-thawed poor-quality blastocyst transfer. When only poor-quality blastocysts are available, selecting those derived from day 3 good-quality embryo for transfer may expedite the process of achieving a live birth.\u003c/p\u003e","manuscriptTitle":"Day 3 embryo quality is a predictor for the clinical pregnancy rate and live birth rate in single frozen- thawed poor-quality blastocyst transfer","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-30 06:12:51","doi":"10.21203/rs.3.rs-4313510/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"84b141c7-86dc-424c-a1c0-8e9b0b233946","owner":[],"postedDate":"April 30th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-08-09T00:23:14+00:00","versionOfRecord":[],"versionCreatedAt":"2024-04-30 06:12:51","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4313510","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4313510","identity":"rs-4313510","version":["v1"]},"buildId":"cTy_lsJlmDsVRNrSptgXS","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}