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:To investigate the prevalence of chronic endometritis(CE)in patients with repeated implantation failure(RIF),and the correlation between diagnostic indexes of CE and classification of peripheral blood immune cells.Methods:A total of 64 patients with RIF who visited Outpatient of Hebei Reproductive Health Hospital from January 2020 to December 2021 were retrospec-tively analyzed.General information of patients,results of hysteroscopy and endometrial immunohistochemistry in the mid luteal phase,the number and percentage of NK cells,Th1 cells,Th2 cells,Th17 cells and Treg cells in peripheral blood,and Th1/Th2,Th17/Treg were collected,and the pregnancy outcome of retransplantation was followed up.To evaluate the consistency of hysteroscopy and endometrial immunohistochemistry CD138 in diagnosis of CE in RIF patients,to analyze whether chronic inflammation of endome-trium was related to classification of peripheral blood immune cells,and to analyze the pregnancy outcome of patients with RIF diag-nosed with CE after retransplantation.Results:Prevalence of CE in RIF patients detected by hysteroscopy was 53.12%,which was sig-nificantly higher than that detected by endometrial immunohistochemistry CD138(25.00%,P<0.05).There was no significant differ-ence in the number and percentage of immune cells in peripheral blood between CE and non CE patients.After antibiotic treatment,the 12-week continuous pregnancy rate and live birth rate in the CD138 positive group were higher than those in negative group,with a statistically significant difference(P<0.05).Conclusion:The combination of hysteroscopy and endometrial CD138 immunohistochem-istry at the right time for RIF patients is beneficial to improve their pregnancy rate and pregnancy outcome.The infiltration of endome-trial plasma cells does not affect the classification of peripheral blood immune cells.

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:To investigate the prevalence of chronic endometritis(CE)in patients with repeated implantation failure(RIF),and the correlation between diagnostic indexes of CE and classification of peripheral blood immune cells.Methods:A total of 64 patients with RIF who visited Outpatient of Hebei Reproductive Health Hospital from January 2020 to December 2021 were retrospec-tively analyzed.General information of patients,results of hysteroscopy and endometrial immunohistochemistry in the mid luteal phase,the number and percentage of NK cells,Th1 cells,Th2 cells,Th17 cells and Treg cells in peripheral blood,and Th1/Th2,Th17/Treg were collected,and the pregnancy outcome of retransplantation was followed up.To evaluate the consistency of hysteroscopy and endometrial immunohistochemistry CD138 in diagnosis of CE in RIF patients,to analyze whether chronic inflammation of endome-trium was related to classification of peripheral blood immune cells,and to analyze the pregnancy outcome of patients with RIF diag-nosed with CE after retransplantation.Results:Prevalence of CE in RIF patients detected by hysteroscopy was 53.12%,which was sig-nificantly higher than that detected by endometrial immunohistochemistry CD138(25.00%,P<0.05).There was no significant differ-ence in the number and percentage of immune cells in peripheral blood between CE and non CE patients.After antibiotic treatment,the 12-week continuous pregnancy rate and live birth rate in the CD138 positive group were higher than those in negative group,with a statistically significant difference(P<0.05).Conclusion:The combination of hysteroscopy and endometrial CD138 immunohistochem-istry at the right time for RIF patients is beneficial to improve their pregnancy rate and pregnancy outcome.The infiltration of endome-trial plasma cells does not affect the classification of peripheral blood immune cells.

Purpose: This study aimed to identify the altered pathways and genes associated with freezing damage in human sperm during cryopreservation by multiomics analysis. Materials and Methods: Fifteen fresh human semen samples were collected for transcriptomic analysis, and another 5 fresh human semen samples were obtained for metabolomic analysis. For each semen sample, 1 mL was cryopreserved, and another 1 mL was left untreated for paired design. The results were then combined with previously published proteomic results to identify key genes/pathways. Results: Cryopreservation significantly reduced sperm motility and mitochondrial structure. Transcriptomic analysis revealed altered mitochondrial function, including changes in tRNA-methyltransferase activity and adenosine tri-phosphate/adenosine di-phosphate transmembrane transporter activity. Metabolomic analysis showed that the citrate cycle in mitochondria was significantly altered. Combining transcriptomic, proteomic, and metabolomic analyses revealed 346 genes that were altered in at least two omics analyses. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that metabolic pathways were significantly altered and strongly associated with mitochondria. Five genes were altered in all three omics analyses: COL11A1, COL18A1, LPCAT3, NME1, and NNT. Conclusions Five genes were identified by multiomics analysis in human cryopreserved sperm. These genes might have specific functions in cryopreservation. Explorations of the functions of these genes will be helpful for sperm cryopreservation and sperm motility improvement or even for reproduction in the future.

Objective:To detect the expression levels of various immune cells in peripheral blood,and to ex-plore their relationship with unexplained recurrent spontaneous abortion(URSA)and its clinical significance in di-agnosis and treatment.Methods:A total of 351 patients with URSA who visited Hebei Reproductive Health Hospi-tal between January 2020 and September 2022 were enrolled as the URSA group,while a control group compri-sing 30 healthy women who had experienced uncomplicated term delivery once and had no history of adverse pregnancy outcomes during the same period was selected.The levels of various immune cell subsets in peripheral blood during the luteal phase were measured and compared between the two groups.Receiver operating charac-teristic(ROC)curve analysis was performed to determine the optimal cutoff values of immune cell levels that could assist in URSA diagnosis and treatment,while logistic regression analysis was conducted to identify factors influ-encing URSA occurrence.Results:The number and percentage of CD3+CD8+cells in the peripheral blood of the URSA group were significantly lower compared to those in the control group(P＜0.05).Conversely,the per-centage of NK cells was significantly higher in the URSA group than in the control group(P＜0.05).Logistic re-gression analysis revealed that the increase in CD3+CD8+cell count in peripheral blood during the luteal phase was a protective factor of URSA(OR＜1,P＜0.05).ROC curve analysis determined optimal cutoff values for im-mune cell levels to assist in the diagnosing and treating URSA:702.82 cells/μl for CD3+CD8+cell count,28.39％for CD3+CD8+cell percentage,and 12.33％for NK cell percentage.After using the optimal cutoff value to convert continuous variables into binary variables,Logistic regression analysis showed that a CD3+CD8+cell count＜702.82 cells/μl and an NK cell percentage＞12.33％were independent risk factors for URSA(OR＞1,P＜0.05).Conclusions:The decrease of CD3+CD8+cells in peripheral blood during midluteal phase is closely related to the occurrence of URSA.The number of CD3+CD8+cells(702.82 cells/μl)and the percentage of NK cells(12.33％)can be used as reference values for the diagnosis and treatment of URSA.

Objective:To detect the expression levels of various immune cells in peripheral blood,and to ex-plore their relationship with unexplained recurrent spontaneous abortion(URSA)and its clinical significance in di-agnosis and treatment.Methods:A total of 351 patients with URSA who visited Hebei Reproductive Health Hospi-tal between January 2020 and September 2022 were enrolled as the URSA group,while a control group compri-sing 30 healthy women who had experienced uncomplicated term delivery once and had no history of adverse pregnancy outcomes during the same period was selected.The levels of various immune cell subsets in peripheral blood during the luteal phase were measured and compared between the two groups.Receiver operating charac-teristic(ROC)curve analysis was performed to determine the optimal cutoff values of immune cell levels that could assist in URSA diagnosis and treatment,while logistic regression analysis was conducted to identify factors influ-encing URSA occurrence.Results:The number and percentage of CD3+CD8+cells in the peripheral blood of the URSA group were significantly lower compared to those in the control group(P＜0.05).Conversely,the per-centage of NK cells was significantly higher in the URSA group than in the control group(P＜0.05).Logistic re-gression analysis revealed that the increase in CD3+CD8+cell count in peripheral blood during the luteal phase was a protective factor of URSA(OR＜1,P＜0.05).ROC curve analysis determined optimal cutoff values for im-mune cell levels to assist in the diagnosing and treating URSA:702.82 cells/μl for CD3+CD8+cell count,28.39％for CD3+CD8+cell percentage,and 12.33％for NK cell percentage.After using the optimal cutoff value to convert continuous variables into binary variables,Logistic regression analysis showed that a CD3+CD8+cell count＜702.82 cells/μl and an NK cell percentage＞12.33％were independent risk factors for URSA(OR＞1,P＜0.05).Conclusions:The decrease of CD3+CD8+cells in peripheral blood during midluteal phase is closely related to the occurrence of URSA.The number of CD3+CD8+cells(702.82 cells/μl)and the percentage of NK cells(12.33％)can be used as reference values for the diagnosis and treatment of URSA.

Objective:To detect the expression levels of various immune cells in peripheral blood,and to ex-plore their relationship with unexplained recurrent spontaneous abortion(URSA)and its clinical significance in di-agnosis and treatment.Methods:A total of 351 patients with URSA who visited Hebei Reproductive Health Hospi-tal between January 2020 and September 2022 were enrolled as the URSA group,while a control group compri-sing 30 healthy women who had experienced uncomplicated term delivery once and had no history of adverse pregnancy outcomes during the same period was selected.The levels of various immune cell subsets in peripheral blood during the luteal phase were measured and compared between the two groups.Receiver operating charac-teristic(ROC)curve analysis was performed to determine the optimal cutoff values of immune cell levels that could assist in URSA diagnosis and treatment,while logistic regression analysis was conducted to identify factors influ-encing URSA occurrence.Results:The number and percentage of CD3+CD8+cells in the peripheral blood of the URSA group were significantly lower compared to those in the control group(P＜0.05).Conversely,the per-centage of NK cells was significantly higher in the URSA group than in the control group(P＜0.05).Logistic re-gression analysis revealed that the increase in CD3+CD8+cell count in peripheral blood during the luteal phase was a protective factor of URSA(OR＜1,P＜0.05).ROC curve analysis determined optimal cutoff values for im-mune cell levels to assist in the diagnosing and treating URSA:702.82 cells/μl for CD3+CD8+cell count,28.39％for CD3+CD8+cell percentage,and 12.33％for NK cell percentage.After using the optimal cutoff value to convert continuous variables into binary variables,Logistic regression analysis showed that a CD3+CD8+cell count＜702.82 cells/μl and an NK cell percentage＞12.33％were independent risk factors for URSA(OR＞1,P＜0.05).Conclusions:The decrease of CD3+CD8+cells in peripheral blood during midluteal phase is closely related to the occurrence of URSA.The number of CD3+CD8+cells(702.82 cells/μl)and the percentage of NK cells(12.33％)can be used as reference values for the diagnosis and treatment of URSA.