The effect of elective single blastocyst transfer and elective double cleavage- stage embryo transfer on clinical pregnancy and live birth rates in fresh cycles

The effect of elective single blastocyst transfer and elective double cleavage- stage embryo transfer on clinical pregnancy and live birth rates in fresh cycles | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article The effect of elective single blastocyst transfer and elective double cleavage- stage embryo transfer on clinical pregnancy and live birth rates in fresh cycles Linjun Chen, Yue Ji, Lihua Zhu, Fei Lin, Junshun Fang, Jie Wang, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4552590/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract More than one embryo transferred into the uterus is likely to result in higher clinical pregnancy and live birth rates, but can also result in a higher rate of multiple pregnancy and births. Single blastocyst transfer can significantly reduce the rate of multiple pregnancies. The present study analyzed a total of 2941 fresh transfer cycles, including 1548 SBT cycles and 1393 DET cycles. Clinical pregnancy, twin pregnancy and live birth rates of the two groups were compared. Overall, the rates of clinical pregnancy and live birth in the DET group were significantly higher than those in the SBT group (75.1% vs. 71.3%, P =0.020; 66.6% vs. 63.0%, P =0.041). A sensitive analysis showed that DET lifted the rates of clinical pregnancy and live birth for patients with aged less than 35 years (aOR 1.792, 95% CI 1.455-2.207; aOR 1.572, 95% CI 1.301-1.901) but not for patients with age 35 years and over (aOR 0.879, 95% CI 0.530-1.457; aOR 1.004, 95% CI 0.614-1.643). The twin pregnancy rate in the SBT group was significantly lower than that in the DET group at all ages (aOR 32.502, 95% CI 21.885-48.269; aOR 23.504, 95% CI 7.714-71.608). SBT can lead to acceptable clinical pregnancy and live birth rates compared with DET and significantly reduce the twin pregnancy rate. Health sciences/Medical research/Outcomes research Health sciences/Medical research/Study design Health sciences/Diseases/Reproductive disorders/Infertility Single blastocyst transfer Double cleavage-stage embryo transfer Clinical pregnancy Twin pregnancy Live birth Figures Figure 1 Introduction Since the first live birth of an in vitro fertilization (IVF) baby in 1978, assisted reproductive technology (ART) has helped thousands of infertile couples conceive their own children. To date, more than 9 million children worldwide have been born through ART 1 . As an ART treatment, multiple embryo transfer with more than one embryo transferred into the uterus is likely to result in higher clinical pregnancy and live birth rates, but can also result in a higher rate of multiple pregnancy and births. Multiple pregnancy is associated with adverse outcomes among both the mother and infants, including pregnancy-induced hypertension, gestational diabetes mellitus, preeclampsia, premature rupture of membranes, preterm birth, low birth weight and birth defects 2-5 . All of these factors increase perinatal and neonatal morbidity and mortality. The risks of hospitalization, outpatient visits and medical procedures are higher for multiples than for singletons, and average hospital costs during the first 5 years of life are 3.3-fold higher for multiples than for singletons 6 . These impose a financial burden on families and consume healthcare resources. Although reducing the number of transferred embryos can significantly reduce the multiple pregnancy rate, it significantly reduces clinical pregnancy and live birth rates. In particular, a meta-analysis showed that single embryo transfer can significantly reduce the rate of multiple pregnancy, but the clinical pregnancy and live birth rates are also decreased 7 . With the development of embryo culture technology, elective single blastocyst transfer (SBT) has developed to the point where it can significantly decrease the multiple pregnancy rate and achieve a live birth rate comparable to that of double cleavage-stage embryo transfer (DET) 8 . The International Committee for Monitoring Assisted Reproductive Technologies (ICMART) world report showed that the twin-delivery rate of fresh cycles decreased from 20.4% in 2010 to 16.2% in 2014 due to the increase in the single embryo transfer rate from 30.0% in 2010 to 40.0% in 2014 9 . Many infertile couples wish to have their own children when undergoing infertility treatment, especially in situations where they have been infertile for many years and are eager to have a live birth in a shorter period. Therefore, minimizing the time to pregnancy and the birth of healthy children has attracted the attention of physicians. Fresh embryo transfer can provide live births for infertile couples in a shorter period of time than frozen embryo transfer (FET) 10 . The literature described above compared the clinical outcomes of elective single blastocyst transfer in patients undergoing fresh cycles with those of patients undergoing non-elective double cleavage-stage embryo transfer. In our retrospective study with a large sample size, we analyzed the impact of elective single blastocyst transfer and elective double cleavage-stage embryo transfer on clinical pregnancy and live birth rates in patients undergoing fresh cycles. This will provide a reference for the transfer strategy used in fresh cycles. Materials and Methods Patients Informed consent was obtained from all the patients for IVF/intracytoplasmic sperm injection (ICSI) treatments between January 2020 and December 2021 in our reproductive medical center. Patients who underwent elective SBT or elective DET with autologous germ cells in fresh cycles were included in this study. Patients with transferred embryos or blastocysts derived from donor oocytes or sperm and patients with FET cycles were excluded from this study. The present study included 1548 elective SBT cycles and 1393 elective DET cycles (Fig. 1 ). The present study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School (No. 2023-642-01). Controlled ovarian hyperstimulation and oocyte pick-up Several protocols (long gonadotrophin-releasing hormone (GnRH) agonist protocol, prolonged GnRH agonist protocol, GnRH antagonist protocol and Gn protocol) were performed for ovarian stimulation. The recombinant follicle-stimulating hormone (rFSH) starting dose was determined according to the female's age, body mass index (BMI), basal FSH, anti-Müllerian hormone (AMH) and antral follicle count (AFC). Human chorionic gonadotropin (hCG) was administered when at least one follicle was 18 mm or more. Oocyte pick-up was performed by vaginal ultrasound at 36 h after hCG administration. In vitro insemination and embryo culture Cumulus-oocyte complexes were coincubated with 100,000 spermatozoa in 0.5 ml G-IVF PLUS (Vitrolife) for 3 h after oocyte pick-up. Oocytes were denuded 5 h after coincubation, and oocytes with the presence of two polar bodies (2PB) were considered successfully fertilized. Oocytes with one polar body 1 h after denudation were reinseminated by early rescue ICSI. The ICSI procedure was performed according to a routine protocol of our IVF center. Fertilization observation was performed 16–18 h after insemination, and oocytes with 2PB and two pronuclei (PN) were considered normal fertilized zygotes. Embryos were cultured with G1/G2-PLUS sequential medium (Vitrolife) in a saturated humidity incubator at 37 ℃ under the conditions of 6% CO 2 , 5% O 2 , and 89% N 2 . Embryo assessment and embryo transfer Cleavage-stage embryos were assessed based on the cell number of embryos, evenness of the blastomeres and fragmentation of embryos. Blastocysts were assessed based on the degree of expansion and the grades of the inner cell mass (ICM) and trophectoderm (TE). The transferred blastocysts were divided into three grades: good-quality (IV-VAA/IV-VAB/IV-VBA), fair-quality (III-VBB), and poor-quality (III-IVAC/III-IVBC/III-IVCA/III-IVCB). Elective single blastocyst transfer referred to at least one day 5 blastocyst that could be cryopreserved after transfer and a cleavage-stage embryo had been cryopreserved preemptively on day 3. Elective double cleavage-stage embryo transfer referred to at least one day 3 embryo that could be cryopreserved after transfer. Elective single blastocyst or two cleavage-stage embryos were transferred to the uterus guided by ultrasound. Surplus embryos were vitrified on day 3 after insemination. Surplus expanded blastocysts shrunk with a laser were vitrified on day 5 or day 6 after insemination. Vitrification kits (KITAZATO) were used for the vitrification of surplus embryos or blastocysts. Follow-up All definitions were performed according to the reported literature 11 . In brief, clinical pregnancy was defined as a pregnancy diagnosed by ultrasonographic visualization of one or more gestational sacs with the presence of fetal heartbeats. Ectopic pregnancy was defined as a pregnancy outside the uterine cavity. Miscarriage was defined as the loss of an intrauterine pregnancy prior to 22 completed weeks of gestation. Live birth was defined as the complete expulsion or extraction from a woman of a product of fertilization with evidence of life after 22 completed weeks of gestation. All data, including clinical pregnancy and live birth outcomes, were obtained from infertile patients by telephone. Statistical analysis SPSS 22.0 software was used to analyze the data. Continuous variables, including female age, female BMI, duration of infertility, basal FSH, AMH, antral follicle count (AFC), rFSH starting dose, rFSH total dose, number of retrieved oocytes, number of 2PN zygotes, number of usable embryos and thickness of endometrium, are presented as the mean ± SD and were compared using an independent samples Mann-Whitney U test. Categorical variables, including the pattern of infertility, ovarian stimulation type, pattern of insemination, clinical pregnancy, twin pregnancy, ectopic pregnancy, miscarriage, termination of pregnancy, ongoing pregnancy and live birth, are presented as percentages and were compared using the chi-square or Fisher's exact test. A logistic regression analysis was used to analyze the correlation between clinical pregnancy, twin pregnancy and live birth rates and confounding factors. P < 0.05 indicates a significant difference. Results As shown in Table 1, female age, proportion of primary infertility, basal FSH, rFSH starting dose and rFSH total dose were significantly lower in the SBT group than those in the DET group, and AMH concentration, AFC, number of retrieved oocytes, proportion of IVF, number of 2PN zygotes and number of usable embryos were significantly higher in the SBT group than those in the DET group. There were no significant differences in female BMI, duration of infertility, basal LH, ovarian stimulation type or thickness of endometrium between the two groups. Table 1. Maternal and cycle characteristics between the two groups. BMI body mass index , FSH follicle-stimulating hormone , LH luteinizing hormone , AMH anti-Müllerian hormone , rFSH recombinant follicle-stimulating hormone , GnRH gonadotrophin-releasing hormone , Gn gonadotropin , IVF in vitro fertilization , ICSI intracytoplasmic sperm injection . SBT DET P value Number of transfer cycles, n 1548 1393 — Female age (years) 30.2±3.6 30.5±4.1 0.043 Female BMI (kg/m 2 ) 23.0±3.3 23.3±3.2 0.065 Duration of infertility (years) 3.3±2.3 3.3±2.4 0.508 Pattern of infertility Primary, n (%) 785(50.7) 808(58.0) <0.001 Secondary, n (%) 763(49.3) 585(42.0) <0.001 Basal FSH (IU/L) 6.6±1.6 6.9±1.8 <0.001 Basal LH (IU/L) 6.1±4.8 5.9±3.3 0.319 AMH (ng/mL) 4.0±2.2 3.5±2.1 <0.001 Antral follicle counts 21.5±11.7 18.4±7.6 <0.001 rFSH starting dose (IU/L) 134.7±45.0 163.6±68.3 <0.001 rFSH total dose (IU/L) 1976.1±657.8 2140.2±664.7 <0.001 Ovarian stimulation type Long GnRH agonist protocol, n (%) 1489(96.2) 1322(94.9) 0.106 Prolonged GnRH agonist protocol, n (%) 55(3.6) 57(4.1) 0.500 GnRH antagonist protocol, n (%) — 11(0.8) — Gn protocol, n (%) 4(0.3) 3(0.2) 1.000 Number of retrieved oocytes 12.7±3.9 11.0±3.8 <0.001 Pattern of insemination IVF, n (%) 1285(83.0) 1037(74.4) <0.001 ICSI, n (%) 263(17.0) 356(25.6) <0.001 Number of 2PN zygotes 10.1±3.3 8.3±3.2 <0.001 Number of usable embryos 6.7±2.4 5.3±2.0 <0.001 Thickness of endometrium (mm) 12.1±2.6 12.0±2.6 0.195 Average number of transferred embryos, n 1 2 — The grades of the transferred embryos or blastocysts in the two groups are shown in Table 2. In the SBT group, the proportion of fully expanded (IV+V) blastocysts in the transferred blastocysts reached 98.7% according to the degree of blastocyst expansion. The proportion of good-quality and fair-quality blastocysts according to the grades of the ICM and TE reached 35.1% and 60.3%, respectively. In the DET group, the proportion of transferred embryos with 8 or more cells reached 97.6%. The proportion of transferred embryos with uniform blastomeres reached 89.0%. The proportion of transferred embryos with less than 10% fragmentation reached 83.0%. Therefore, more than 80% of the transferred embryos in the DET group were good-quality embryos. Table 2. Grades of transferred embryos or blastocysts in the two groups SBT DET Number of transferred embryos, n 1548 2786 Day 3 embryo grade — Embryo cell number — 8cell, n (%) — 921(33.1) Blastomere uniformity — Even, n (%) — 2480(89.0) Uneven, n (%) — 306(11.0) Embryo fragmentation — <10%, n (%) — 2313(83.0) 10-25%, n (%) — 473(17.0) Blastocysts grade — Expansion grade — Ⅲ, n (%) 20(1.3) — Ⅳ, n (%) 1501(97.0) — Ⅴ, n (%) 27(1.7) — Good quality (Ⅳ-ⅤAA/Ⅳ-ⅤAB/Ⅳ-ⅤBA), n (%) 544(35.1) — Fair quality (Ⅲ-ⅤBB), n (%) 933(60.3) — Poor quality (Ⅲ-ⅣAC/Ⅲ-ⅣBC/Ⅲ-ⅣCA/Ⅲ-ⅣCB), n (%) 71(4.6) — The clinical outcomes of the two groups are shown in Table 3. The rates of clinical pregnancy and live birth in the DET group were significantly higher than those in the SBT group (75.1% vs. 71.3%, P =0.020; 66.6% vs. 63.0%, P =0.041). The rate of twin pregnancy in the SBT group was significantly lower than that in the DET group (2.3% vs. 37.0%, P <0.001). The rates of ectopic pregnancy, miscarriage, termination of pregnancy and ongoing pregnancy were not significantly different between the two groups. Table 3. Clinical outcomes in the two groups. SBT DET P value Number of transfer cycles, n 1548 1393 — Number of clinical pregnancy cycles, n (%) 1103(71.3) a 1046(75.1) 0.020 Number of twin pregnancy cycles, n (%) 36(2.3) 516(37.0) <0.001 Number of ectopic pregnancy cycles, n (%) 5(0.5) 10(1.0) 0.199 Number of miscarriage cycles, n (%) 115(10.4) 96(9.2) 0.346 Number of termination of pregnancy cycles, n (%) 8(0.7) 11(1.1) 0.493 Number of ongoing pregnancy cycles, n (%) 975(88.4) 929(88.8) 0.786 Number of live birth cycles (per transfer cycle), n (%) 975(63.0) 928(66.6) 0.041 The results of the logistic regression analysis of clinical pregnancy, twin pregnancy and live birth rates after adjustments for confounding factors according to the maternal and cycle characteristics are shown in Table 4. Female age, number of transferred embryos, ovarian stimulation type, number of 2PN zygotes and number of usable embryos were significant factors affecting clinical pregnancy rate. Female age, number of transferred embryos, basal LH, AFC and number of usable embryos were significant factors affecting twin pregnancy rate. Female age, number of transferred embryos, rFSH starting dose, ovarian stimulation type and endometrial thickness were significant factors affecting live birth rate. Among these significant factors, female age and the number of transferred embryos simultaneously affected the rates of clinical pregnancy, twin pregnancy and live birth. Table 4. Results of the logistic regression analysis of clinical pregnancy, twin pregnancy and live birth rates after adjustments for confounding factors according to the maternal and cycle characteristics. PN pronuclei , LH luteinizing hormone , rFSH recombinant follicle-stimulating hormone . Adjusted OR 95% CI P value Clinical pregnancy Female age 0.953 0.930-0.977 <0.001 Number of transferred embryos 1.542 1.277-1.863 <0.001 Ovarian stimulation type 0.634 0.460-0.874 0.005 Number of 2PN zygotes 0.942 0.890-0.998 0.042 Number of usable embryos 1.108 1.049-1.171 <0.001 Twin pregnancy Female age 0.927 0.898-0.957 <0.001 Number of transferred embryos 30.655 21.165-44.401 <0.001 Basal LH 1.025 1.001-1.050 0.038 Antral follicle counts 0.978 0.957-0.999 0.038 Number of usable embryos 1.095 1.021-1.175 0.012 Live birth Female age 0.948 0.927-0.970 <0.001 Number of transferred embryos 1.431 1.202-1.704 <0.001 rFSH starting dose 0.997 0.996-0.999 0.001 Ovarian stimulation type 0.685 0.498-0.942 0.020 Thickness of endometrium 1.046 1.012-1.081 0.007 The impact of the number of transferred embryos on clinical pregnancy, twin pregnancy and live birth rates by age stratification are shown in Table 5. For females aged less than 35 years, the rates of clinical pregnancy and live birth in the DET group were significantly higher than those in the SBT group (adjusted OR (aOR) 1.792, 95% CI 1.455-2.207; aOR 1.572, 95% CI 1.301-1.901). For females aged 35 years and over, the rates of clinical pregnancy and live birth in the DET group were not significantly different compared with those in the SBT group (aOR 0.879, 95% CI 0.530-1.457; aOR 1.004, 95% CI 0.614-1.643). The twin pregnancy rate in the SBT group was significantly lower than that in the DET group at all ages (aOR 32.502, 95% CI 21.885-48.269; aOR 23.504, 95% CI 7.714-71.608). Table 5. The impact of the number of transferred embryos on clinical pregnancy, twin pregnancy and live birth rates by age stratification. Adjusted OR 95% CI P value < 35 Clinical pregnancy 1.792 1.455-2.207 <0.001 Twin pregnancy 32.502 21.885-48.269 <0.001 Live birth 1.572 1.301-1.901 <0.001 ≥ 35 Clinical pregnancy 0.879 0.530-1.457 0.617 Twin pregnancy 23.504 7.714-71.608 <0.001 Live birth 1.004 0.614-1.643 0.986 Discussion The present study compared the rates of clinical pregnancy, twin pregnancy and live birth between the SBT and DET groups. Overall, the rates of clinical pregnancy and live birth in the DET group were significantly higher than those in the SBT group. After age stratification, the rates of clinical pregnancy and live birth for females aged less than 35 years in the SBT group were significantly lower than those in the DET group. The rates of clinical pregnancy and live birth for females aged 35 years and over were not significantly different between the two groups. The twin pregnancy rate in the SBT group was significantly lower than that in the DET group at all ages. Kwek et al. 12 reported that SBT had similar clinical pregnancy and live birth rates to those of DET. The present study showed that the clinical pregnancy and live birth rates in the DET group were significantly higher than those in the SBT group. This may be related to the positive correlation between embryo quality and clinical pregnancy and live birth rates 13 , 14 . This is because DET in our retrospective study was elective DET. The infertile couples had at least one cleavage-stage embryo for cryopreservation after undergoing DET. This may be the reason why the clinical and live birth rates in the DET group were significantly higher than those in the SBT group. Moreover, the quality of the transferred embryos (embryo cell number, blastomere uniformity and embryo fragmentation) 15 or blastocysts (the degree of blastocyst expansion, the quality of inner cell masses and trophectoderm) can affect clinical outcomes during IVF/ICSI treatments 16 . The embryos in the DET group and blastocysts in the SBT group that were chosen for transfer were the best ones in terms of morphological assessment. Except for inconsistent developmental stages, there was no selection bias in terms of embryonic morphology for the transferred embryos or blastocysts between the two groups. Female age was an independent factor affecting the outcomes during IVF/ICSI treatment. Female age affected the rates of blastocyst formation and euploid blastocysts 17 , 18 . In our retrospective study, a sensitive analysis showed that DET lifted the rates of clinical pregnancy and live birth for patients with aged less than 35 years but not for patients with age 35 years and over. This may be related to the fact that the cleavage-stage embryos of females aged less than 35 years had better potential to develop into blastocysts and led to better clinical outcomes. The cleavage-stage embryos of females aged 35 years and over had poor potential to develop into blastocysts and led to poor clinical outcomes. This is because advanced maternal age can alter the expression of maternal effect genes and compromise oocyte quality 19 , which is the main determinant of embryo developmental potential 20 . Advanced maternal age is also correlated with delayed embryonic development and abnormal cleavage patterns and has negative effects on morphokinetic parameters by a time-lapse imaging system 21 – 23 . Advanced maternal age also has adverse effects on the mitochondrial function of human morulae, leading to a decline in the developmental rate from morulae to blastocysts 24 . Therefore, it was reported that better clinical outcomes can be obtained by blastocyst transfer for patients with advanced maternal age 25 , 26 . In the DET group, the rates of clinical pregnancy, twin pregnancy and live birth of females aged less than 35 years were significantly higher than those of females aged 35 years and over. This further indicates that embryos derived from females aged less than 35 years have better developmental potential and better clinical outcomes than those of females aged 35 years and over. The results of our retrospective study demonstrated that there was a negative correlation between female age and embryonic developmental potential, which is consistent with the reported literature 17 . In addition to affecting embryonic developmental potential, female age also affects clinical outcomes 27 – 29 . The present study showed that the live birth rate of females aged less than 35 years in the SBT group was significantly higher than that of females aged 35 years and over. This suggests that advanced maternal age can significantly reduce the live birth rate even if high-quality blastocysts are transferred. This may be related to the negative correlation between maternal age and the rate of euploid blastocysts 18 , as well as the fact that advanced maternal age increases the risk of embryonic chromosomal abnormalities, leading to a decrease in the live birth rate 30 , 31 . In our retrospective study, none of transferred blastocysts were subjected to preimplantation genetic testing for aneuploidy, so it was not possible to explain from the perspective of blastocyst ploidy that patients with advanced maternal age had significantly reduced live birth rates. However, it has been reported that the live birth rate significantly decreases as maternal age increases, even when euploid blastocysts are transferred 28 , 29 . There may also be factors other than aneuploidy affecting the live birth rate for patients with advanced maternal age. Therefore, the mechanism of the influence of advanced maternal age on the live birth rate requires further research. The present study had some limitations. First, the nature of a single-center retrospective study was one of the limitations. Differences in sample size between females aged less than 35 years and females aged 35 years and over within the group led to a significantly higher overall clinical pregnancy and live birth rate in the DET groups than in the SBT group. This hid the impact of female age on clinical outcomes and the advantages of blastocyst transfer for patients with advanced maternal age. All transferred embryos or blastocysts in the present study were assessed based on morphology rather than morphokinetic parameters by a time-lapse imaging system. This was a limitation of the present study. Furthermore, the present study only compared and analyzed the outcomes following the embryo transfer. Patients who initially intended to undergo single blastocyst transfer but ultimately did not have an embryo transfer for any reason were not included in the present study, which may introduce a bias and potentially skew the conclusions. This is also a limitation of our retrospective study. In conclusion, SBT can result in acceptable clinical pregnancy and live birth rates compared with DET and significantly reduce the twin pregnancy rate. Declarations Author Contribution Shanshan Wang and Jie Wang contributed to the conception and design of the study. Linjun Chen and Yue Ji wrote the manuscript. Lihua Zhu contributed to data acquisition. Fei Lin and Junshun Fang contributed to data interpretation and analysis. All authors read and approved the final manuscript. Data Availability The raw data supporting the conclusions of this article will be available from the corresponding author on reasonable request. References Westvik-Johari, K. et al . 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(Engl). 131 (11), 1261-1267. https://doi.org/10.4103/0366-6999.232808 (2018). Ezoe, K. et al . Maternal age affects pronuclear and chromatin dynamics, morula compaction and cell polarity, and blastulation of human embryos. Hum. Reprod. 38 (3), 387-399. https://doi.org/10.1093/humrep/dead001 (2023). La Marca, A. et al . Female age, serum antimüllerian hormone level, and number of oocytes affect the rate and number of euploid blastocysts in in vitro fertilization/intracytoplasmic sperm injection cycles. Fertil. Steril. 108 (5), 777-783.e2. https://doi.org/10.1016/j.fertnstert.2017.08.029 (2017). Zhang, J.J. et al . Advanced maternal age alters expression of maternal effect genes that are essential for human oocyte quality. Aging (Albany NY). 12 (4), 3950-3961. https://doi.org/10.18632/aging.102864 (2020). Keefe, D., Kumar, M. & Kalmbach, K. Oocyte competency is the key to embryo potential. Fertil. Steril. 103 (2), 317-322. https://doi.org/10.1016/j.fertnstert.2014.12.115 (2015). 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Effects of endometrial preparations and transferred embryo types on pregnancy outcome from patients with advanced maternal age. Syst. Biol. Reprod. Med. 65 (2), 181-186. https://doi.org/10.1080/19396368.2018.1501114 (2019). Sotiroska ,V. et al . The day of embryo transfer affects delivery rate, birth weights, female-to-male ratio, and monozygotic twin rate. Taiwan J. Obstet. Gynecol. 54 (6), 716-721. https://doi.org/10.1016/j.tjog.2015.06.011 (2015). Sun, Y.F. et al . Effects of age on pregnancy outcomes in patients with simple tubal factor infertility receiving frozen-thawed embryo transfer. Sci. Rep. 10 (1), 18121. https://doi.org/10.1038/s41598-020-75124-3 (2020). Zhang, W.Y., Johal, J.K., Gardner, R.M., Bavan, B. & Milki, A.A. The impact of euploid blastocyst morphology and maternal age on pregnancy and neonatal outcomes in natural cycle frozen embryo transfers. J. Assist. Reprod. Genet. 39 (3), 647-654. https://doi.org/10.1007/s10815-022-02423-1 (2022). Reig, A., Franasiak, J., Scott, R.T. Jr. & Seli, E. The impact of age beyond ploidy: outcome data from 8175 euploid single embryo transfers. J. Assist. Reprod. Genet. 37 (3), 595-602. https://doi.org/10.1007/s10815-020-01739-0 (2020). Qi, S.T., Liang, L.F., Xian, Y.X., Liu, J.Q. & Wang, W. Arrested human embryos are more likely to have abnormal chromosomes than developing embryos from women of advanced maternal age. J. Ovarian. Res. 7 , 65. https://doi.org/10.1186/1757-2215-7-65 (2014). Shi, W.H. et al . Different Strategies of Preimplantation Genetic Testing for Aneuploidies in Women of Advanced Maternal Age: A Systematic Review and Meta-Analysis. J. Clin. Med. 10 (17), 3895. https://doi.org/10.3390/jcm10173895 (2021). Additional Declarations No competing interests reported. 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To date, more than 9 million children worldwide have been born through ART\u003csup\u003e1\u003c/sup\u003e. As an ART treatment, multiple embryo transfer with more than one embryo transferred into the uterus is likely to result in higher clinical pregnancy and live birth rates, but can also result in a higher rate of multiple pregnancy and births. Multiple pregnancy is associated with adverse outcomes among both the mother and infants, including pregnancy-induced hypertension, gestational diabetes mellitus, preeclampsia, premature rupture of membranes, preterm birth, low birth weight and birth defects\u003csup\u003e2-5\u003c/sup\u003e. All of these factors increase perinatal and neonatal morbidity and mortality. The risks of hospitalization, outpatient visits and medical procedures are higher for multiples than for singletons, and average hospital costs during the first 5 years of life are 3.3-fold higher for multiples than for singletons\u003csup\u003e6\u003c/sup\u003e. These impose a financial burden on families and consume healthcare resources.\u003c/p\u003e\n\u003cp\u003eAlthough reducing the number of transferred embryos can significantly reduce the multiple pregnancy rate, it significantly reduces clinical pregnancy and live birth rates. In particular, a meta-analysis showed that single embryo transfer can significantly reduce the rate of multiple pregnancy, but the clinical pregnancy and live birth rates are also decreased\u003csup\u003e7\u003c/sup\u003e. With the development of embryo culture technology, elective single blastocyst transfer (SBT) has developed to the point where it can significantly decrease the multiple pregnancy rate and achieve a live birth rate comparable to that of double cleavage-stage embryo transfer (DET)\u003csup\u003e8\u003c/sup\u003e. The International Committee for Monitoring Assisted Reproductive Technologies (ICMART) world report showed that the twin-delivery rate of fresh cycles decreased from 20.4% in 2010 to 16.2% in 2014 due to the increase in the single embryo transfer rate from 30.0% in 2010 to 40.0% in 2014\u003csup\u003e9\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eMany infertile couples wish to have their own children when undergoing infertility treatment, especially in situations where they have been infertile for many years and are eager to have a live birth in a shorter period. Therefore, minimizing the time to pregnancy and the birth of healthy children has attracted the attention of physicians. Fresh embryo transfer can provide live births for infertile couples in a shorter period of time than frozen embryo transfer (FET)\u003csup\u003e10\u003c/sup\u003e. The literature described above compared the clinical outcomes of elective single blastocyst transfer in patients undergoing fresh cycles with those of patients undergoing non-elective double cleavage-stage embryo transfer. In our retrospective study with a large sample size, we analyzed the impact of elective single blastocyst transfer and elective double cleavage-stage embryo transfer on clinical pregnancy and live birth rates in patients undergoing fresh cycles. This will provide a reference for the transfer strategy used in fresh cycles.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec2\" class=\"Section2\"\u003e \u003ch2\u003ePatients\u003c/h2\u003e \u003cp\u003e \u003cstrong\u003eInformed consent\u003c/strong\u003e \u003cp\u003ewas obtained from all the patients for IVF/intracytoplasmic sperm injection (ICSI) treatments between January 2020 and December 2021 in our reproductive medical center. Patients who underwent elective SBT or elective DET with autologous germ cells in fresh cycles were included in this study. Patients with transferred embryos or blastocysts derived from donor oocytes or sperm and patients with FET cycles were excluded from this study. The present study included 1548 elective SBT cycles and 1393 elective DET cycles (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The present study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School (No. 2023-642-01).\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eControlled ovarian hyperstimulation and oocyte pick-up\u003c/h2\u003e \u003cp\u003eSeveral protocols (long gonadotrophin-releasing hormone (GnRH) agonist protocol, prolonged GnRH agonist protocol, GnRH antagonist protocol and Gn protocol) were performed for ovarian stimulation. The recombinant follicle-stimulating hormone (rFSH) starting dose was determined according to the female's age, body mass index (BMI), basal FSH, anti-M\u0026uuml;llerian hormone (AMH) and antral follicle count (AFC). Human chorionic gonadotropin (hCG) was administered when at least one follicle was 18 mm or more. Oocyte pick-up was performed by vaginal ultrasound at 36 h after hCG administration.\u003c/p\u003e \u003cdiv id=\"Sec4\" class=\"Section3\"\u003e \u003ch2\u003eIn vitro insemination and embryo culture\u003c/h2\u003e \u003cp\u003eCumulus-oocyte complexes were coincubated with 100,000 spermatozoa in 0.5 ml G-IVF PLUS (Vitrolife) for 3 h after oocyte pick-up. Oocytes were denuded 5 h after coincubation, and oocytes with the presence of two polar bodies (2PB) were considered successfully fertilized. Oocytes with one polar body 1 h after denudation were reinseminated by early rescue ICSI. The ICSI procedure was performed according to a routine protocol of our IVF center. Fertilization observation was performed 16\u0026ndash;18 h after insemination, and oocytes with 2PB and two pronuclei (PN) were considered normal fertilized zygotes. Embryos were cultured with G1/G2-PLUS sequential medium (Vitrolife) in a saturated humidity incubator at 37 ℃ under the conditions of 6% CO\u003csub\u003e2\u003c/sub\u003e, 5% O\u003csub\u003e2\u003c/sub\u003e, and 89% N\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eEmbryo assessment and embryo transfer\u003c/h2\u003e \u003cp\u003eCleavage-stage embryos were assessed based on the cell number of embryos, evenness of the blastomeres and fragmentation of embryos. Blastocysts were assessed based on the degree of expansion and the grades of the inner cell mass (ICM) and trophectoderm (TE). The transferred blastocysts were divided into three grades: good-quality (IV-VAA/IV-VAB/IV-VBA), fair-quality (III-VBB), and poor-quality (III-IVAC/III-IVBC/III-IVCA/III-IVCB). Elective single blastocyst transfer referred to at least one day 5 blastocyst that could be cryopreserved after transfer and a cleavage-stage embryo had been cryopreserved preemptively on day 3. Elective double cleavage-stage embryo transfer referred to at least one day 3 embryo that could be cryopreserved after transfer. Elective single blastocyst or two cleavage-stage embryos were transferred to the uterus guided by ultrasound. Surplus embryos were vitrified on day 3 after insemination. Surplus expanded blastocysts shrunk with a laser were vitrified on day 5 or day 6 after insemination. Vitrification kits (KITAZATO) were used for the vitrification of surplus embryos or blastocysts.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eFollow-up\u003c/h3\u003e\n\u003cp\u003eAll definitions were performed according to the reported literature\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. In brief, clinical pregnancy was defined as a pregnancy diagnosed by ultrasonographic visualization of one or more gestational sacs with the presence of fetal heartbeats. Ectopic pregnancy was defined as a pregnancy outside the uterine cavity. Miscarriage was defined as the loss of an intrauterine pregnancy prior to 22 completed weeks of gestation. Live birth was defined as the complete expulsion or extraction from a woman of a product of fertilization with evidence of life after 22 completed weeks of gestation. All data, including clinical pregnancy and live birth outcomes, were obtained from infertile patients by telephone.\u003c/p\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eSPSS 22.0 software was used to analyze the data. Continuous variables, including female age, female BMI, duration of infertility, basal FSH, AMH, antral follicle count (AFC), rFSH starting dose, rFSH total dose, number of retrieved oocytes, number of 2PN zygotes, number of usable embryos and thickness of endometrium, are presented as the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD and were compared using an independent samples Mann-Whitney U test. Categorical variables, including the pattern of infertility, ovarian stimulation type, pattern of insemination, clinical pregnancy, twin pregnancy, ectopic pregnancy, miscarriage, termination of pregnancy, ongoing pregnancy and live birth, are presented as percentages and were compared using the chi-square or Fisher's exact test. A logistic regression analysis was used to analyze the correlation between clinical pregnancy, twin pregnancy and live birth rates and confounding factors. \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05 indicates a significant difference.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eAs shown in Table 1, female age, proportion of primary infertility, basal FSH, rFSH starting dose and rFSH total dose were significantly lower in the SBT group than those in the DET group, and AMH concentration, AFC, number of retrieved oocytes, proportion of IVF, number of 2PN zygotes and number of usable embryos were significantly higher in the SBT group than those in the DET group. There were no significant differences in female BMI, duration of infertility, basal LH, ovarian stimulation type or thickness of endometrium between the two groups.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1.\u0026nbsp;\u003c/strong\u003eMaternal and cycle characteristics between the two groups. \u003cem\u003eBMI\u0026nbsp;\u003c/em\u003ebody mass index\u003cem\u003e, FSH\u0026nbsp;\u003c/em\u003efollicle-stimulating hormone\u003cem\u003e, LH\u0026nbsp;\u003c/em\u003eluteinizing hormone\u003cem\u003e, AMH\u0026nbsp;\u003c/em\u003eanti-M\u0026uuml;llerian hormone\u003cem\u003e, rFSH\u0026nbsp;\u003c/em\u003erecombinant follicle-stimulating hormone\u003cem\u003e, GnRH\u0026nbsp;\u003c/em\u003egonadotrophin-releasing hormone\u003cem\u003e, Gn\u0026nbsp;\u003c/em\u003egonadotropin\u003cem\u003e, IVF\u0026nbsp;\u003c/em\u003ein vitro fertilization\u003cem\u003e, ICSI\u0026nbsp;\u003c/em\u003eintracytoplasmic sperm injection\u003cem\u003e.\u003c/em\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"475\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eSBT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eDET\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eP\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of transfer\u0026nbsp;cycles, n\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e1548\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e1393\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eFemale age (years)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e30.2\u0026plusmn;3.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e30.5\u0026plusmn;4.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e0.043\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eFemale BMI (kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e23.0\u0026plusmn;3.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e23.3\u0026plusmn;3.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e0.065\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eDuration of infertility (years)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e3.3\u0026plusmn;2.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e3.3\u0026plusmn;2.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e0.508\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003ePattern of infertility\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003ePrimary, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e785(50.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e808(58.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eSecondary, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e763(49.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e585(42.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eBasal FSH (IU/L)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e6.6\u0026plusmn;1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e6.9\u0026plusmn;1.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eBasal LH (IU/L)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e6.1\u0026plusmn;4.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e5.9\u0026plusmn;3.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e0.319\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eAMH (ng/mL)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e4.0\u0026plusmn;2.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e3.5\u0026plusmn;2.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eAntral follicle counts\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e21.5\u0026plusmn;11.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e18.4\u0026plusmn;7.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003erFSH starting dose (IU/L)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e134.7\u0026plusmn;45.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e163.6\u0026plusmn;68.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003erFSH total dose (IU/L)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e1976.1\u0026plusmn;657.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e2140.2\u0026plusmn;664.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eOvarian stimulation type\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eLong GnRH agonist protocol, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e1489(96.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e1322(94.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e0.106\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eProlonged GnRH agonist protocol, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e55(3.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e57(4.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e0.500\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eGnRH antagonist protocol, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e11(0.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eGn protocol, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e4(0.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e3(0.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of retrieved oocytes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e12.7\u0026plusmn;3.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e11.0\u0026plusmn;3.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003ePattern of insemination\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eIVF, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e1285(83.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e1037(74.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eICSI, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e263(17.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e356(25.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of 2PN zygotes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e10.1\u0026plusmn;3.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e8.3\u0026plusmn;3.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of usable embryos\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e6.7\u0026plusmn;2.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e5.3\u0026plusmn;2.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eThickness of endometrium (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e12.1\u0026plusmn;2.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e12.0\u0026plusmn;2.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e0.195\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"40%\" valign=\"top\"\u003e\n \u003cp\u003eAverage number of transferred embryos, n\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.789473684210527%\" valign=\"top\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.42105263157895%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cp\u003eThe grades of the transferred embryos or blastocysts in the two groups are shown in Table 2. In the SBT group, the proportion of fully expanded (IV+V) blastocysts in the transferred blastocysts reached 98.7% according to the degree of blastocyst expansion. The proportion of good-quality and fair-quality blastocysts according to the grades of the ICM and TE reached 35.1% and 60.3%, respectively. In the DET group, the proportion of transferred embryos with 8 or more cells reached 97.6%. The proportion of transferred embryos with uniform blastomeres reached 89.0%. The proportion of transferred embryos with less than 10% fragmentation reached 83.0%. Therefore, more than 80% of the transferred embryos in the DET group were good-quality embryos.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eTable 2.\u0026nbsp;\u003c/strong\u003eGrades of transferred embryos or blastocysts in the two groups\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"556\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eSBT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eDET\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of transferred embryos, n\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e1548\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\"\u003e\n \u003cp\u003e2786\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003eDay 3 embryo grade\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003eEmbryo cell number\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;8cell, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e69(2.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003e8cell, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e1796(64.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026gt;8cell, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e921(33.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003eBlastomere uniformity\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003eEven, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e2480(89.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003eUneven, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e306(11.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003eEmbryo fragmentation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;10%, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e2313(83.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003e10-25%, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e473(17.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003eBlastocysts grade\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003eExpansion grade\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003eⅢ, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e20(1.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003eⅣ, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e1501(97.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003eⅤ, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e27(1.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003eGood quality (Ⅳ-ⅤAA/Ⅳ-ⅤAB/Ⅳ-ⅤBA), n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e544(35.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003eFair quality (Ⅲ-ⅤBB), n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e933(60.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"54.31654676258993%\" valign=\"top\"\u003e\n \u003cp\u003ePoor quality (Ⅲ-ⅣAC/Ⅲ-ⅣBC/Ⅲ-ⅣCA/Ⅲ-ⅣCB), n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e71(4.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"22.841726618705035%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe clinical outcomes of the two groups are shown in Table 3. The rates of clinical pregnancy and live birth in the DET group were significantly higher than those in the SBT group (75.1% vs. 71.3%, \u003cem\u003eP\u003c/em\u003e=0.020; 66.6% vs. 63.0%, \u003cem\u003eP\u003c/em\u003e=0.041). The rate of twin pregnancy in the SBT group was significantly lower than that in the DET group (2.3% vs. 37.0%, \u003cem\u003eP\u003c/em\u003e\u0026lt;0.001). The rates of ectopic pregnancy, miscarriage, termination of pregnancy and ongoing pregnancy were not significantly different between the two groups.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003cstrong\u003eTable 3.\u0026nbsp;\u003c/strong\u003eClinical outcomes in the two groups.\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"542\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"49.2619926199262%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eSBT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eDET\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.15867158671587%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eP\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003evalue\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"49.2619926199262%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of transfer cycles, n\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e1548\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\"\u003e\n \u003cp\u003e1393\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.15867158671587%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026mdash;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"49.2619926199262%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of clinical pregnancy cycles, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e1103(71.3)\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e1046(75.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.15867158671587%\" valign=\"top\"\u003e\n \u003cp\u003e0.020\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"49.2619926199262%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of twin pregnancy cycles, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;36(2.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e516(37.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.15867158671587%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"49.2619926199262%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of ectopic pregnancy cycles, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e5(0.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e10(1.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.15867158671587%\" valign=\"top\"\u003e\n \u003cp\u003e0.199\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"49.2619926199262%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of miscarriage cycles, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e115(10.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e96(9.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.15867158671587%\" valign=\"top\"\u003e\n \u003cp\u003e0.346\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"49.2619926199262%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of termination of pregnancy cycles, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e8(0.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e11(1.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.15867158671587%\" valign=\"top\"\u003e\n \u003cp\u003e0.493\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"49.2619926199262%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of ongoing pregnancy cycles, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e975(88.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e929(88.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.15867158671587%\" valign=\"top\"\u003e\n \u003cp\u003e0.786\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"49.2619926199262%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of live birth cycles (per transfer cycle), n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e975(63.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.789667896678967%\" valign=\"top\"\u003e\n \u003cp\u003e928(66.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.15867158671587%\" valign=\"top\"\u003e\n \u003cp\u003e0.041\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe results of the logistic regression analysis of clinical pregnancy, twin pregnancy and live birth rates after adjustments for confounding factors according to the maternal and cycle characteristics are shown in Table 4. Female age, number of transferred embryos, ovarian stimulation type, number of 2PN zygotes and number of usable embryos were significant factors affecting clinical pregnancy rate. Female age, number of transferred embryos, basal LH, AFC and number of usable embryos were significant factors affecting twin pregnancy rate. Female age, number of transferred embryos, rFSH starting dose, ovarian stimulation type and endometrial thickness were significant factors affecting live birth rate. Among these significant factors, female age and the number of transferred embryos simultaneously affected the rates of clinical pregnancy, twin pregnancy and live birth.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cstrong\u003eTable 4.\u0026nbsp;\u003c/strong\u003eResults of the logistic regression analysis of clinical pregnancy, twin pregnancy and live birth rates after adjustments for confounding factors according to the maternal and cycle characteristics. \u003cem\u003ePN\u0026nbsp;\u003c/em\u003epronuclei\u003cem\u003e, LH\u0026nbsp;\u003c/em\u003eluteinizing hormone\u003cem\u003e, rFSH\u0026nbsp;\u003c/em\u003erecombinant follicle-stimulating hormone\u003cem\u003e.\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"529\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eAdjusted OR\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e95% CI\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eP\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eClinical pregnancy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eFemale age\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e0.953\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e0.930-0.977\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of transferred embryos\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e1.542\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e1.277-1.863\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eOvarian stimulation type\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e0.634\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e0.460-0.874\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e0.005\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of 2PN zygotes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e0.942\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e0.890-0.998\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e0.042\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of usable embryos\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e1.108\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e1.049-1.171\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eTwin pregnancy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eFemale age\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e0.927\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e0.898-0.957\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of transferred embryos\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e30.655\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e21.165-44.401\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eBasal LH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e1.025\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e1.001-1.050\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e0.038\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eAntral follicle counts\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e0.978\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e0.957-0.999\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e0.038\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of usable embryos\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e1.095\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e1.021-1.175\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e0.012\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eLive birth\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eFemale age\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e0.948\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e0.927-0.970\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eNumber of transferred embryos\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e1.431\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e1.202-1.704\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003erFSH starting dose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e0.997\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e0.996-0.999\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eOvarian stimulation type\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e0.685\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e0.498-0.942\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e0.020\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.29545454545455%\" valign=\"top\"\u003e\n \u003cp\u003eThickness of endometrium\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.803030303030305%\" valign=\"top\"\u003e\n \u003cp\u003e1.046\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.401515151515152%\" valign=\"top\"\u003e\n \u003cp\u003e1.012-1.081\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.5%\" valign=\"top\"\u003e\n \u003cp\u003e0.007\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe impact of the number of transferred embryos on clinical pregnancy, twin pregnancy and live birth rates by age stratification are shown in Table 5. For females aged less than 35 years, the rates of clinical pregnancy and live birth in the DET group were significantly higher than those in the SBT group (adjusted OR (aOR) 1.792, 95% CI 1.455-2.207; aOR 1.572, 95% CI 1.301-1.901). For females aged 35 years and over, the rates of clinical pregnancy and live birth in the DET group were not significantly different compared with those in the SBT group (aOR 0.879, 95% CI 0.530-1.457; aOR 1.004, 95% CI 0.614-1.643). The twin pregnancy rate in the SBT group was significantly lower than that in the DET group at all ages (aOR 32.502, 95% CI 21.885-48.269; aOR 23.504, 95% CI 7.714-71.608).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cstrong\u003eTable 5.\u0026nbsp;\u003c/strong\u003eThe impact of the number of transferred embryos on clinical pregnancy, twin pregnancy and live birth rates by age stratification.\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"552\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.369565217391305%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.297101449275363%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eAdjusted OR\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.21014492753623%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e95% CI\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.1231884057971%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eP\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.369565217391305%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt; 35\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.297101449275363%\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.21014492753623%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.1231884057971%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.369565217391305%\" valign=\"top\"\u003e\n \u003cp\u003eClinical pregnancy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.297101449275363%\" valign=\"top\"\u003e\n \u003cp\u003e1.792\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.21014492753623%\" valign=\"top\"\u003e\n \u003cp\u003e1.455-2.207\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.1231884057971%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.369565217391305%\" valign=\"top\"\u003e\n \u003cp\u003eTwin pregnancy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.297101449275363%\" valign=\"top\"\u003e\n \u003cp\u003e32.502\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.21014492753623%\" valign=\"top\"\u003e\n \u003cp\u003e21.885-48.269\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.1231884057971%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.369565217391305%\" valign=\"top\"\u003e\n \u003cp\u003eLive birth\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.297101449275363%\" valign=\"top\"\u003e\n \u003cp\u003e1.572\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.21014492753623%\" valign=\"top\"\u003e\n \u003cp\u003e1.301-1.901\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.1231884057971%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.369565217391305%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026ge; 35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.297101449275363%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.21014492753623%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.1231884057971%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.369565217391305%\" valign=\"top\"\u003e\n \u003cp\u003eClinical pregnancy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.297101449275363%\" valign=\"top\"\u003e\n \u003cp\u003e0.879\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.21014492753623%\" valign=\"top\"\u003e\n \u003cp\u003e0.530-1.457\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.1231884057971%\" valign=\"top\"\u003e\n \u003cp\u003e0.617\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.369565217391305%\" valign=\"top\"\u003e\n \u003cp\u003eTwin pregnancy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.297101449275363%\" valign=\"top\"\u003e\n \u003cp\u003e23.504\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.21014492753623%\" valign=\"top\"\u003e\n \u003cp\u003e7.714-71.608\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.1231884057971%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"48.369565217391305%\" valign=\"top\"\u003e\n \u003cp\u003eLive birth\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.297101449275363%\" valign=\"top\"\u003e\n \u003cp\u003e1.004\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.21014492753623%\" valign=\"top\"\u003e\n \u003cp\u003e0.614-1.643\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.1231884057971%\" valign=\"top\"\u003e\n \u003cp\u003e0.986\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe present study compared the rates of clinical pregnancy, twin pregnancy and live birth between the SBT and DET groups. Overall, the rates of clinical pregnancy and live birth in the DET group were significantly higher than those in the SBT group. After age stratification, the rates of clinical pregnancy and live birth for females aged less than 35 years in the SBT group were significantly lower than those in the DET group. The rates of clinical pregnancy and live birth for females aged 35 years and over were not significantly different between the two groups. The twin pregnancy rate in the SBT group was significantly lower than that in the DET group at all ages.\u003c/p\u003e \u003cp\u003eKwek et al.\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e reported that SBT had similar clinical pregnancy and live birth rates to those of DET. The present study showed that the clinical pregnancy and live birth rates in the DET group were significantly higher than those in the SBT group. This may be related to the positive correlation between embryo quality and clinical pregnancy and live birth rates\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. This is because DET in our retrospective study was elective DET. The infertile couples had at least one cleavage-stage embryo for cryopreservation after undergoing DET. This may be the reason why the clinical and live birth rates in the DET group were significantly higher than those in the SBT group. Moreover, the quality of the transferred embryos (embryo cell number, blastomere uniformity and embryo fragmentation)\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e or blastocysts (the degree of blastocyst expansion, the quality of inner cell masses and trophectoderm) can affect clinical outcomes during IVF/ICSI treatments\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. The embryos in the DET group and blastocysts in the SBT group that were chosen for transfer were the best ones in terms of morphological assessment. Except for inconsistent developmental stages, there was no selection bias in terms of embryonic morphology for the transferred embryos or blastocysts between the two groups.\u003c/p\u003e \u003cp\u003eFemale age was an independent factor affecting the outcomes during IVF/ICSI treatment. Female age affected the rates of blastocyst formation and euploid blastocysts\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e,\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. In our retrospective study, a sensitive analysis showed that DET lifted the rates of clinical pregnancy and live birth for patients with aged less than 35 years but not for patients with age 35 years and over. This may be related to the fact that the cleavage-stage embryos of females aged less than 35 years had better potential to develop into blastocysts and led to better clinical outcomes. The cleavage-stage embryos of females aged 35 years and over had poor potential to develop into blastocysts and led to poor clinical outcomes. This is because advanced maternal age can alter the expression of maternal effect genes and compromise oocyte quality\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e, which is the main determinant of embryo developmental potential\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. Advanced maternal age is also correlated with delayed embryonic development and abnormal cleavage patterns and has negative effects on morphokinetic parameters by a time-lapse imaging system\u003csup\u003e\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. Advanced maternal age also has adverse effects on the mitochondrial function of human morulae, leading to a decline in the developmental rate from morulae to blastocysts\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. Therefore, it was reported that better clinical outcomes can be obtained by blastocyst transfer for patients with advanced maternal age\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e,\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. In the DET group, the rates of clinical pregnancy, twin pregnancy and live birth of females aged less than 35 years were significantly higher than those of females aged 35 years and over. This further indicates that embryos derived from females aged less than 35 years have better developmental potential and better clinical outcomes than those of females aged 35 years and over. The results of our retrospective study demonstrated that there was a negative correlation between female age and embryonic developmental potential, which is consistent with the reported literature\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIn addition to affecting embryonic developmental potential, female age also affects clinical outcomes\u003csup\u003e\u003cspan additionalcitationids=\"CR28\" citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. The present study showed that the live birth rate of females aged less than 35 years in the SBT group was significantly higher than that of females aged 35 years and over. This suggests that advanced maternal age can significantly reduce the live birth rate even if high-quality blastocysts are transferred. This may be related to the negative correlation between maternal age and the rate of euploid blastocysts\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e, as well as the fact that advanced maternal age increases the risk of embryonic chromosomal abnormalities, leading to a decrease in the live birth rate\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e,\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. In our retrospective study, none of transferred blastocysts were subjected to preimplantation genetic testing for aneuploidy, so it was not possible to explain from the perspective of blastocyst ploidy that patients with advanced maternal age had significantly reduced live birth rates. However, it has been reported that the live birth rate significantly decreases as maternal age increases, even when euploid blastocysts are transferred\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e,\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. There may also be factors other than aneuploidy affecting the live birth rate for patients with advanced maternal age. Therefore, the mechanism of the influence of advanced maternal age on the live birth rate requires further research.\u003c/p\u003e \u003cp\u003eThe present study had some limitations. First, the nature of a single-center retrospective study was one of the limitations. Differences in sample size between females aged less than 35 years and females aged 35 years and over within the group led to a significantly higher overall clinical pregnancy and live birth rate in the DET groups than in the SBT group. This hid the impact of female age on clinical outcomes and the advantages of blastocyst transfer for patients with advanced maternal age. All transferred embryos or blastocysts in the present study were assessed based on morphology rather than morphokinetic parameters by a time-lapse imaging system. This was a limitation of the present study. Furthermore, the present study only compared and analyzed the outcomes following the embryo transfer. Patients who initially intended to undergo single blastocyst transfer but ultimately did not have an embryo transfer for any reason were not included in the present study, which may introduce a bias and potentially skew the conclusions. This is also a limitation of our retrospective study.\u003c/p\u003e \u003cp\u003eIn conclusion, SBT can result in acceptable clinical pregnancy and live birth rates compared with DET and significantly reduce the twin pregnancy rate.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eShanshan Wang and Jie Wang contributed to the conception and design of the study. Linjun Chen and Yue Ji wrote the manuscript. Lihua Zhu contributed to data acquisition. Fei Lin and Junshun Fang contributed to data interpretation and analysis. All authors read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe raw data supporting the conclusions of this article will be available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eWestvik-Johari, K. \u003cem\u003eet al\u003c/em\u003e. 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Med.\u003c/em\u003e\u003cstrong\u003e10\u003c/strong\u003e(17), 3895. https://doi.org/10.3390/jcm10173895 (2021).\u003c/li\u003e\n\u003c/ol\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, Double cleavage-stage embryo transfer, Clinical pregnancy, Twin pregnancy, Live birth","lastPublishedDoi":"10.21203/rs.3.rs-4552590/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4552590/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eMore than one embryo transferred into the uterus is likely to result in higher clinical pregnancy and live birth rates, but can also result in a higher rate of multiple pregnancy and births. Single blastocyst transfer can significantly reduce the rate of multiple pregnancies. The present study analyzed a total of 2941 fresh transfer cycles, including 1548 SBT cycles and 1393 DET cycles. Clinical pregnancy, twin pregnancy and live birth rates of the two groups were compared. Overall, the rates of clinical pregnancy and live birth in the DET group were significantly higher than those in the SBT group (75.1% vs. 71.3%, \u003cem\u003eP\u003c/em\u003e=0.020; 66.6% vs. 63.0%, \u003cem\u003eP\u003c/em\u003e=0.041). A sensitive analysis showed that DET lifted the rates of clinical pregnancy and live birth for patients with aged less than 35 years (aOR 1.792, 95% CI 1.455-2.207; aOR 1.572, 95% CI 1.301-1.901) but not for patients with age 35 years and over (aOR 0.879, 95% CI 0.530-1.457; aOR 1.004, 95% CI 0.614-1.643). The twin pregnancy rate in the SBT group was significantly lower than that in the DET group at all ages (aOR 32.502, 95% CI 21.885-48.269; aOR 23.504, 95% CI 7.714-71.608). SBT can lead to acceptable clinical pregnancy and live birth rates compared with DET and significantly reduce the twin pregnancy rate.\u003c/p\u003e","manuscriptTitle":"The effect of elective single blastocyst transfer and elective double cleavage- stage embryo transfer on clinical pregnancy and live birth rates in fresh cycles","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-07-18 18:22:16","doi":"10.21203/rs.3.rs-4552590/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":"a39c9900-5981-44ea-a114-e3bf71392ae5","owner":[],"postedDate":"July 18th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":34223061,"name":"Health sciences/Medical research/Outcomes research"},{"id":34223062,"name":"Health sciences/Medical research/Study design"},{"id":34223063,"name":"Health sciences/Diseases/Reproductive disorders/Infertility"}],"tags":[],"updatedAt":"2024-08-14T17:46:15+00:00","versionOfRecord":[],"versionCreatedAt":"2024-07-18 18:22:16","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4552590","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4552590","identity":"rs-4552590","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}