With advancements in in vitro culture techniques, the morula has emerged as a promising candidate for selective embryo transfer due to its critical compaction phase. The compaction process involves not only structural reorganization but also complex intercellular signaling mechanisms that significantly influence embryonic developmental potential and cellular fate determination. Clinical data reveal comparable live birth rates between day 4 morula transfers and day 5 blastocyst transfers, coupled with reduced in vitro culture duration. However, challenges persist regarding standardized evaluation criteria and long-term safety confirmation. Current morphological assessment methods exhibit inherent subjectivity, while emerging technologies integrating genetic screening, metabolic analysis, and time-lapse imaging show potential for enhanced selection accuracy. Personalized synchronization assessments, including endometrial receptivity analysis, may further optimize transfer protocols. This study focuses on day 4 embryo transfer, systematically reviewing its embryonic development processes, evaluation protocols, comparative outcomes of transferred embryos, and research advances in frozen-thawed embryo transfer. The study aims to deepen scientific understanding of day 4 embryo transfer and promote its adoption as a critical option in personalized reproductive medicine, thereby enhancing clinical success rates and safety.

Objective:To establish a day 4 embryo evaluation protocol by analyzing embryonic characteristics affecting blastocyst formation, and validate its clinical effectiveness.Methods:This retrospective cohort study included clinical data from 1 037 patients who underwent fresh in vitro fertilization and embryo transfer (IVF-ET) on day 4 in Center for Reproductive Medicine of Xingtai Meihe Reproductive and Genetic Hospital between January 2018 and April 2024. Morphological assessments were performed at (92±2) h post-fertilization. After excluding 1 326 embryos selected for fresh transfer, 2 723 embryos underwent blastocyst culture. To address selection bias in transferred embryos, the scoring system was primarily based on high-quality blastocyst formation rates. Multivariate binary regression analysis evaluated how day 4 developmental stage, fragmentation rate, stage-specific cleavage patterns, multinucleation/vacuolization affected transferable blastocyst formation rate and high-quality blastocyst rate. Regression coefficients determined parameter weights for high-quality blastocyst formation, establishing a day 4 embryo scoring protocol that compared outcomes across different grades. The scoring system was validated by comparing transferable blastocyst formation rate, high-quality blastocyst rate, and implantation rate among different day 4 embryo grades. All embryos were further rescored according to three previously reported evaluation schemes [Feil 2008, Gemma 2015, and European Society of Human Reproduction and Embryology (ESHRE) 2011]. The predictive values of these three day 4 scoring systems and the day 4 scoring system established in this study were compared using the area under the curve (AUC) receiver operating characteristic (ROC) curve in predicting the formation rate of transferable blastocyst, the formation rate of high-quality blastocyst, and implantation rate. Results:In the prediction of high-quality blastocyst formation, early blastocyst showed the highest influence weight compared to embryos with the ratio of blastomere numbers on day 4 to those on day 3 (BNR) <1.2 ( B=3.398, OR=29.915, P<0.001), followed by fragmentation <10% versus ≥50% ( B=1.263, OR=3.535, P<0.001), a stage-specific cleavage pattern ( B=0.903, OR=2.467, P=0.005), and absence of multinucleation or vacuoles ( B=0.797, OR=2.218, P=0.007). Using the newly developed day 4 scoring system, embryos were graded A, B, C, D, E. Transferable blastocyst formation rates were 88.57% (279/315), 76.99% (241/313), 56.11% (280/499), 40.27% (238/591) and 14.22% (143/1 005), respectively; high-quality blastocyst rates were 51.42% (162/315), 35.46% (111/313), 20.04% (100/499), 9.47% (56/591) and 3.98% (40/1 005). All inter-group differences were statistically significant (all P<0.005). Implantation rates for transferred embryos of grades A-E declined sequentially: 63.18% (381/603), 56.19% (322/573), 38.29% (54/141), 26.53% (13/49) and 9.67% (3/31). The day 4 embryo scoring system proposed in this study demonstrated significantly higher predictive efficacy for transferable blastocyst formation rate (AUC=0.812), high-quality blastocyst formation rate (AUC=0.804), and implantation rate (AUC=0.603) compared with Feil 2008 (AUC=0.797, P<0.001; AUC=0.781, P<0.001; AUC=0.585, P<0.001), Gemma 2015 (AUC=0.773, P<0.001; AUC=0.771, P<0.001; AUC=0.542, P=0.006), and ESHRE 2011 (AUC=0.710, P<0.001; AUC=0.745, P<0.001; AUC=0.592, P<0.001). We also observed the presence of pseudo-compacted embryo, whose transferable blastocyst formation rate [38.28% (49/128)] and high-quality blastocyst formation rate [7.03% (9/128)] were similar to those of cleavage-stage embryos with a BNR≥1.2. Conclusion:The established day 4 morphological assessment system reliably predicts the potential to transferable blastocyst and high-quality blastocyst, and effectively forecasts implantation rates.

With advancements in in vitro culture techniques, the morula has emerged as a promising candidate for selective embryo transfer due to its critical compaction phase. The compaction process involves not only structural reorganization but also complex intercellular signaling mechanisms that significantly influence embryonic developmental potential and cellular fate determination. Clinical data reveal comparable live birth rates between day 4 morula transfers and day 5 blastocyst transfers, coupled with reduced in vitro culture duration. However, challenges persist regarding standardized evaluation criteria and long-term safety confirmation. Current morphological assessment methods exhibit inherent subjectivity, while emerging technologies integrating genetic screening, metabolic analysis, and time-lapse imaging show potential for enhanced selection accuracy. Personalized synchronization assessments, including endometrial receptivity analysis, may further optimize transfer protocols. This study focuses on day 4 embryo transfer, systematically reviewing its embryonic development processes, evaluation protocols, comparative outcomes of transferred embryos, and research advances in frozen-thawed embryo transfer. The study aims to deepen scientific understanding of day 4 embryo transfer and promote its adoption as a critical option in personalized reproductive medicine, thereby enhancing clinical success rates and safety.

Objective:To establish a day 4 embryo evaluation protocol by analyzing embryonic characteristics affecting blastocyst formation, and validate its clinical effectiveness.Methods:This retrospective cohort study included clinical data from 1 037 patients who underwent fresh in vitro fertilization and embryo transfer (IVF-ET) on day 4 in Center for Reproductive Medicine of Xingtai Meihe Reproductive and Genetic Hospital between January 2018 and April 2024. Morphological assessments were performed at (92±2) h post-fertilization. After excluding 1 326 embryos selected for fresh transfer, 2 723 embryos underwent blastocyst culture. To address selection bias in transferred embryos, the scoring system was primarily based on high-quality blastocyst formation rates. Multivariate binary regression analysis evaluated how day 4 developmental stage, fragmentation rate, stage-specific cleavage patterns, multinucleation/vacuolization affected transferable blastocyst formation rate and high-quality blastocyst rate. Regression coefficients determined parameter weights for high-quality blastocyst formation, establishing a day 4 embryo scoring protocol that compared outcomes across different grades. The scoring system was validated by comparing transferable blastocyst formation rate, high-quality blastocyst rate, and implantation rate among different day 4 embryo grades. All embryos were further rescored according to three previously reported evaluation schemes [Feil 2008, Gemma 2015, and European Society of Human Reproduction and Embryology (ESHRE) 2011]. The predictive values of these three day 4 scoring systems and the day 4 scoring system established in this study were compared using the area under the curve (AUC) receiver operating characteristic (ROC) curve in predicting the formation rate of transferable blastocyst, the formation rate of high-quality blastocyst, and implantation rate. Results:In the prediction of high-quality blastocyst formation, early blastocyst showed the highest influence weight compared to embryos with the ratio of blastomere numbers on day 4 to those on day 3 (BNR) <1.2 ( B=3.398, OR=29.915, P<0.001), followed by fragmentation <10% versus ≥50% ( B=1.263, OR=3.535, P<0.001), a stage-specific cleavage pattern ( B=0.903, OR=2.467, P=0.005), and absence of multinucleation or vacuoles ( B=0.797, OR=2.218, P=0.007). Using the newly developed day 4 scoring system, embryos were graded A, B, C, D, E. Transferable blastocyst formation rates were 88.57% (279/315), 76.99% (241/313), 56.11% (280/499), 40.27% (238/591) and 14.22% (143/1 005), respectively; high-quality blastocyst rates were 51.42% (162/315), 35.46% (111/313), 20.04% (100/499), 9.47% (56/591) and 3.98% (40/1 005). All inter-group differences were statistically significant (all P<0.005). Implantation rates for transferred embryos of grades A-E declined sequentially: 63.18% (381/603), 56.19% (322/573), 38.29% (54/141), 26.53% (13/49) and 9.67% (3/31). The day 4 embryo scoring system proposed in this study demonstrated significantly higher predictive efficacy for transferable blastocyst formation rate (AUC=0.812), high-quality blastocyst formation rate (AUC=0.804), and implantation rate (AUC=0.603) compared with Feil 2008 (AUC=0.797, P<0.001; AUC=0.781, P<0.001; AUC=0.585, P<0.001), Gemma 2015 (AUC=0.773, P<0.001; AUC=0.771, P<0.001; AUC=0.542, P=0.006), and ESHRE 2011 (AUC=0.710, P<0.001; AUC=0.745, P<0.001; AUC=0.592, P<0.001). We also observed the presence of pseudo-compacted embryo, whose transferable blastocyst formation rate [38.28% (49/128)] and high-quality blastocyst formation rate [7.03% (9/128)] were similar to those of cleavage-stage embryos with a BNR≥1.2. Conclusion:The established day 4 morphological assessment system reliably predicts the potential to transferable blastocyst and high-quality blastocyst, and effectively forecasts implantation rates.

Objective:Evaluate the safety of the bioresorbable scaffold (BRS) series implanted.Methods:This is a cohort study, which included 377 patients with acute coronary syndrome (ACS) who underwent elective percutaneous coronary intervention (PCI) with Neovas-BRS implantation from July 2019 to April 2022 at the Northern Command General Hospital. The patients were divided into the series BRS group ( n=63) and single BRS group ( n=314). We compared PCI related data between two groups, as well as all-cause death, cardiac death, non-fatal myocardial infarction, target vessel revascularization, stroke, and bleeding of type 2 to 5 defined by the Bleeding Academic Research Consortium of America (BARC) during follow-up. We also compared the major adverse cardiovascular and cerebrovascular events (MACCE), which includes all-cause death, non-fatal myocardial infarction, target vessel revascularization and stroke, as well as the net adverse clinical events (NACE), which includes MACCE and bleeding of BARC type 2 to 5. Procedural immediate success was defined as a residual stenosis of<20% with successful stent implantation and post-PCI target vessel flow grade up to TIMI 3. The images of 11 patients in the series BRS group who underwent optical coherence tomography (OCT) were analyzed. Results:A total of 377 patients were finally enrolled, aged (52.5±10.7) years, including 80.4% (303/377) males . The immediate success rate of PCI was 100% in both groups. The number of ≥50% stenotic lesions, number of target vessels, SYNTAX score, number of post-application expansion balloons, number of guidewires, total stent length, contrast volume and operation time were higher in the series BRS group than in the single BRS group (all P<0.05). There was no significant difference in the proportion of intravascular ultrasound and OCT application between the two groups. One patient in the single BRS group had an ischemic stroke during postoperative hospitalization, but there were no death, non-fatal myocardial infarction, target vessel revascularization, or BARC 2 to 5 bleeding events occurred during hospitalization in both groups. Follow up time was 352.0 (193.0, 421.0) days. There was no statistically significant difference between the two groups in the incidence of all-cause death (0 vs. 0.6% (2/314), P=1.000), cardiogenic death (0 vs. 0.3% (1/314), P=1.000), nonfatal myocardial infarction (0 vs. 1.0% (3/314), P=1.000), target lesion revascularization (3.2% (2/63) vs. 1.6% (5/314), P=0.736), BARC type 2 to 5 bleeding (3.2% (2/63) vs. 5.7% (18/314), P=0.604), MACCE (3.2% (2/63) vs. 2.9% (9/314), P=0.894), and NACE (6.3% (4/63) vs. 8.6% (27/314), P=0.553) during the follow-up period. OCT results of the 11 (17.5%) patients in the series BRS group indicated that 3 patients (27.3%) achieved non-overlapping connection, and the immediate stent expansion rate was (95.47±0.04) %. In 8 patients with BRS overlapping connections, immediate stent expansion rate was (90.32±0.44) %. Conclusion:In patients with low to intermediate-risk ACS, serial implantation of RBS in long coronary lesions is safe and feasible, and achieves the similar short-term outcomes as single BRS implantation.

Objective:To explore the effect of different transplantation schemes on the clinical outcomes and maternal and fetal outcomes of fresh cycle on day 4.Methods:The clinical data of 745 cycles of in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) in Reproductive Medicine Center of Xingtai Infertility Specialist Hospitals from January 2019 to December 2021 were analyzed retrospectively. In all cycles, 1-2 embryos were transferred on day 4 after fertilization. According to different embryo transfer schemes, they were divided into five groups: one partial compaction embryo group (group A, n=17), two partial compaction embryos group (group B, n=236), one full compaction above embryo group (group C, n=241), partial compaction+full compaction above group (group D, n=72), and two full compaction above embryos group (group E, n=179), the effects of different transfer schemes on clinical outcomes and maternal and fetal outcomes were compared. Results:There were no significant differences in two pronuclei (2PN) fertilization rate, 2PN cleavage rate, endometrial thickness, monozygotic twins rate, surgical reduction rate, abortion rate, stillbirth rate, cesarean section rate, male infant/female infant ratio among the five groups (all P>0.05). The clinical pregnancy rate in groups D and E [83.33% (60/72), 72.63% (130/179)] was significantly higher than that in group B [59.32% (140/236), P<0.001, P=0.005]. The live birth rate of group E [65.36% (117/179)] was significantly higher than that of group B [50.00% (118/236), P=0.002]. The implantation rate of groups C, D and E [64.73% (156/241),59.72% (86/144), 54.19% (194/358)] was significantly higher than that of group B [39.83% (188/472), all P<0.001]. The multiple birth rate [43.33% (26/60), 49.23% (64/130)] and the premature delivery rate [23.33% (14/60), 26.15% (34/130)] in groups D and E were significantly higher than those in group C [0%, all P<0.001; 7.69% (12/156), P=0.002, P<0.001]. The gestational weeks of delivery in group E [38.0 (36.0,39.0) weeks] was significantly lower than that in group C [39.0 (38.0,39.3) weeks, P<0.001]. Compared with the one embryo transfer group (group A, group C), the birth weight of the two embryos transfer group (group B, group D, group E) was significantly lower ( P<0.001). The low birth weight infants rate in group D [20.90% (14/67)] and group E [28.40% (48/169)] was significantly higher than that in group C [3.85% (5/130), P<0.001]. Logistic regression analysis showed that after adjusted, the pregnancy rate in group C was significantly higher than that in group A ( OR=0.353, 95% CI: 0.125-0.997, P=0.049). The live birth rate of group E was significantly higher than that of group C ( OR=1.842, 95% CI: 1.172-2.895, P=0.008), and the premature delivery rate of groups B, D and E was significantly higher than that of group C ( OR=2.546, 95% CI: 1.079-6.005, P=0.033; OR=6.737, 95% CI: 2.566-17.689, P<0.001; OR=5.863, 95% CI: 2.494-13.785, P<0.001). Conclusion:On day 4 of the fresh cycle, the pregnancy rate and the live birth rate of the full compaction or above embryos are significantly higher than those of the partial compaction embryos. In clinical work, it is recommended to select full compaction embryos or above, and then select partially compaction embryos for single embryo transfer to achieve optimal pregnancy outcomes while reducing the multiple pregnancy rate, premature delivery rate, and low birth weight infant rate.

Objective:To investigate the effects of day 4 (D4) embryo transfer on clinical outcomes and maternal and infant outcomes in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) in fresh cycles. Methods:We retrospectively analyzed the clinical data of 361 IVF and ICSI cycles from January 2019 to December 2021 in the Reproductive Medicine Center of Xingtai Infertility Specialist Hospitals in a cohort study. In all cycles, one of the best quality embryo was transferred at D4 or D5 after fertilization. The clinical outcomes and maternal and fetal outcomes of D4 transfer group and D5 transfer group were compared.Results:Compared with D4 transfer group, the estradiol value on human chorionic gonadotropin (hCG) injection day significantly increased in D5 transfer group [3 516 (2 273, 4 116) ng/L vs. 2 940 (1 935, 3 877) ng/L, P=0.023], and the luteinizing hormone (LH) value on hCG injection day significantly decreased [0.82 (0.63, 1.11) μg/L vs. 0.94 (0.69, 1.20) μg/L, P=0.026], two pronuclei (2PN) fertilization rate [71.13% (929/1 306)] and the available embryo rate [51.73% (509/984)] in D5 transfer group were significantly higher than those in D4 transfer group [67.26% (2 539/3 775), P=0.010; 48.00% (1 306/2 721), P=0.045]. The clinical pregnancy rate [63.37% (173/273)] and the live birth rate [53.11% (145/273)] in D4 transfer group were significantly higher than those in D5 transfer group [46.59% (41/88), P=0.005; 36.36% (32/88), P=0.006]. There were no significant differences in ectopic pregnancy rate, monozygotic twins rate, abortion rate, preterm birth rate, stillbirth rate, caesarean section rate, delivery gestation, male/female ratio and birth weight (all P>0.05). The results of logistic regression analysis showed that the days of embryo transfer had a significant correlation with the pregnancy rate and the live birth rate ( OR=0.468, 95% CI: 0.266-0.824, P=0.009; OR=0.481, 95% CI: 0.273-0.847, P=0.011). Conclusion:In IVF/ICSI of fresh cycles, the clinical pregnancy rate and the live birth rate of D4 transplantation are better than that of D5 transplantation, and the maternal and fetal outcomes are similar. Therefore, D4 embryo transplantation can be preferred in clinical work.

Objective:To explore the effect of different transplantation schemes on the clinical outcomes and maternal and fetal outcomes of fresh cycle on day 4.Methods:The clinical data of 745 cycles of in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) in Reproductive Medicine Center of Xingtai Infertility Specialist Hospitals from January 2019 to December 2021 were analyzed retrospectively. In all cycles, 1-2 embryos were transferred on day 4 after fertilization. According to different embryo transfer schemes, they were divided into five groups: one partial compaction embryo group (group A, n=17), two partial compaction embryos group (group B, n=236), one full compaction above embryo group (group C, n=241), partial compaction+full compaction above group (group D, n=72), and two full compaction above embryos group (group E, n=179), the effects of different transfer schemes on clinical outcomes and maternal and fetal outcomes were compared. Results:There were no significant differences in two pronuclei (2PN) fertilization rate, 2PN cleavage rate, endometrial thickness, monozygotic twins rate, surgical reduction rate, abortion rate, stillbirth rate, cesarean section rate, male infant/female infant ratio among the five groups (all P>0.05). The clinical pregnancy rate in groups D and E [83.33% (60/72), 72.63% (130/179)] was significantly higher than that in group B [59.32% (140/236), P<0.001, P=0.005]. The live birth rate of group E [65.36% (117/179)] was significantly higher than that of group B [50.00% (118/236), P=0.002]. The implantation rate of groups C, D and E [64.73% (156/241),59.72% (86/144), 54.19% (194/358)] was significantly higher than that of group B [39.83% (188/472), all P<0.001]. The multiple birth rate [43.33% (26/60), 49.23% (64/130)] and the premature delivery rate [23.33% (14/60), 26.15% (34/130)] in groups D and E were significantly higher than those in group C [0%, all P<0.001; 7.69% (12/156), P=0.002, P<0.001]. The gestational weeks of delivery in group E [38.0 (36.0,39.0) weeks] was significantly lower than that in group C [39.0 (38.0,39.3) weeks, P<0.001]. Compared with the one embryo transfer group (group A, group C), the birth weight of the two embryos transfer group (group B, group D, group E) was significantly lower ( P<0.001). The low birth weight infants rate in group D [20.90% (14/67)] and group E [28.40% (48/169)] was significantly higher than that in group C [3.85% (5/130), P<0.001]. Logistic regression analysis showed that after adjusted, the pregnancy rate in group C was significantly higher than that in group A ( OR=0.353, 95% CI: 0.125-0.997, P=0.049). The live birth rate of group E was significantly higher than that of group C ( OR=1.842, 95% CI: 1.172-2.895, P=0.008), and the premature delivery rate of groups B, D and E was significantly higher than that of group C ( OR=2.546, 95% CI: 1.079-6.005, P=0.033; OR=6.737, 95% CI: 2.566-17.689, P<0.001; OR=5.863, 95% CI: 2.494-13.785, P<0.001). Conclusion:On day 4 of the fresh cycle, the pregnancy rate and the live birth rate of the full compaction or above embryos are significantly higher than those of the partial compaction embryos. In clinical work, it is recommended to select full compaction embryos or above, and then select partially compaction embryos for single embryo transfer to achieve optimal pregnancy outcomes while reducing the multiple pregnancy rate, premature delivery rate, and low birth weight infant rate.

Objective:To investigate the effects of day 4 (D4) embryo transfer on clinical outcomes and maternal and infant outcomes in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) in fresh cycles. Methods:We retrospectively analyzed the clinical data of 361 IVF and ICSI cycles from January 2019 to December 2021 in the Reproductive Medicine Center of Xingtai Infertility Specialist Hospitals in a cohort study. In all cycles, one of the best quality embryo was transferred at D4 or D5 after fertilization. The clinical outcomes and maternal and fetal outcomes of D4 transfer group and D5 transfer group were compared.Results:Compared with D4 transfer group, the estradiol value on human chorionic gonadotropin (hCG) injection day significantly increased in D5 transfer group [3 516 (2 273, 4 116) ng/L vs. 2 940 (1 935, 3 877) ng/L, P=0.023], and the luteinizing hormone (LH) value on hCG injection day significantly decreased [0.82 (0.63, 1.11) μg/L vs. 0.94 (0.69, 1.20) μg/L, P=0.026], two pronuclei (2PN) fertilization rate [71.13% (929/1 306)] and the available embryo rate [51.73% (509/984)] in D5 transfer group were significantly higher than those in D4 transfer group [67.26% (2 539/3 775), P=0.010; 48.00% (1 306/2 721), P=0.045]. The clinical pregnancy rate [63.37% (173/273)] and the live birth rate [53.11% (145/273)] in D4 transfer group were significantly higher than those in D5 transfer group [46.59% (41/88), P=0.005; 36.36% (32/88), P=0.006]. There were no significant differences in ectopic pregnancy rate, monozygotic twins rate, abortion rate, preterm birth rate, stillbirth rate, caesarean section rate, delivery gestation, male/female ratio and birth weight (all P>0.05). The results of logistic regression analysis showed that the days of embryo transfer had a significant correlation with the pregnancy rate and the live birth rate ( OR=0.468, 95% CI: 0.266-0.824, P=0.009; OR=0.481, 95% CI: 0.273-0.847, P=0.011). Conclusion:In IVF/ICSI of fresh cycles, the clinical pregnancy rate and the live birth rate of D4 transplantation are better than that of D5 transplantation, and the maternal and fetal outcomes are similar. Therefore, D4 embryo transplantation can be preferred in clinical work.

Objective:To investigate the development of embryos cultured and pregnancy outcomes after in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) under medium incubated with low oxygen (5% oxygen concentration) and high oxygen (20% oxygen concentration) one day in advance. Methods:We retrospectively analyzed the data of 881 IVF/ICSI cycles from August 2018 to September 2019 in the Reproductive Medicine Center of Xingtai Infertility Specialist Hospital. The culture medium was prepared one day in advance and placed in an incubator for balance. According to the oxygen concentration in the incubator, it was divided into low oxygen balance group (5% oxygen concentration) and high oxygen balance group (20% oxygen concentration). The effects of two different medium balanced environments on embryonic development and pregnancy outcomes under two insemination methods were compared.Results:The number of oocytes retrieved, the fertilization rate, the two pronucleus (2PN) cleavage rate and the vailable embryo rate were not significantly different between the two groups of IVF and ICSI (all P>0.05). There was no significant difference on day 3 (D3) available embryo rate between the two groups of IVF, but it was significantly higher in the low oxygen balance group than in the high oxygen balance group of ICSI [68.52% (664/969) vs. 64.42% (795/1234), P=0.043]. The available blastocyst rate of the low oxygen balance group were significantly higher than that in the high oxygen balance group in IVF and ICSI [IVF: 44.99% (808/1796) vs. 41.45% (841/2029), P=0.027; ICSI: 42.00% (307/731) vs. 34.95% (317/907), P=0.004]. The number of transferred embryos in the low oxygen balance group was significantly lower than that in the high oxygen balance group in IVF and ICSI (IVF: 1.87±0.34 vs. 1.96±0.21, P=0.001; ICSI: 1.79±0.41 vs. 1.94±0.23, P=0.002). The implantation rate, the clinical pregnancy rate, and the live birth rate were not significantly different between the two groups of IVF and ICSI. Logistic regression showed that liquid balance environment was related to live birth rate ( OR=0.238, 95% CI=0.139-0.409, P<0.001). Conclusion:Compared with the high oxygen, medium incubated in the low oxygen (5% O 2 concentration) can enhance the developmental potential of embryos, significantly enhance live birth rate, and ICSI is more effective than IVF. But the exact results still need to be confirmed by a large sample of randomized controlled studies.