When inflammation is continuously activated or dysregulated， it can induce chronic tissue injury and organ dysfunction， and participate in the occurrence and development of various inflammatory diseases such as atherosclerosis and inflammatory bowel disease. Owing to high targeting， long-acting efficacy and programmability， nucleic acid drugs provide a new direction for the treatment of inflammatory diseases. This article reviews the classification， mechanism of action and application progress of nucleic acid drugs in inflammatory diseases. It is found that small interfering RNA （siRNA） can specifically cut target mRNA through RNA interference to achieve inhibiting the expression of the target protein； antisense oligonucleotide （ASO） can inhibit target protein expression by inducing microRNA （miRNA） degradation or regulating splicing processes； miRNA can achieve network intervention by regulating multiple inflammatory target genes. At present， important breakthroughs have been made in the field of inflammatory diseases with siRNA drugs including Lumasiran， Nedosiran （for primary hyperoxaluria 1） and Inclisiran （for atherosclerosis）， ASO drugs including Donidalorsen （for hereditary angioedema）， Volanesorsen and Olezarsen （for familial chylomicronemia syndrome） and Lademirsen （for Alport syndrome）， as well as miRNA drugs including Obefazimod （for inflammatory bowel disease） and Remlarsen （for pathological fibrosis）. These drugs are expected to become a new generation of anti-inflammatory therapeutic strategies and bring more precise and efficient treatment options for patients with chronic inflammation and fibrotic diseases.

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 effect of verbascoside(VERB)on high-fat diet-induced atherosclerosis(AS)in ApoE-/-mice and the effect on high mobility histone 1(HMGB1)/receptor for glycation end products(RAGE)/nuclear factor κB(NF-κB)pathway.Methods:A total of 90 ApoE-/-mice were randomly divided into normal group,AS group,VERB group,simvastatin group and VERB+pathway activator HMGB1 group,with 18 mice per group.After 8 weeks of group administration,blood and aorta samples were taken.Fasting serum triacylglycerol(TG),total cholesterol(TC)and low density lipoprotein(LDL)levels were deter-mined by automatic biochemical analyzer.Oil red O,HE and TUNEL staining were performed to observe apoptosis of aortic plaque and endothelial cell(EC).Flow cytometry was performed to analyze circulating EC numbers.Immunohistochemistry was performed to analyze the infiltration area of macrophages(CD68+)and T lymphocytes(CD3+)in aortic plaques.Western blot was performed to detect expressions of HMGB1/RAGE/NF-κB pathway,inflammation and adhesion molecules.Results:Compared with normal group,AS group had lipid plaques in arterial intima,thickness of the media was uneven,TG,TC,LDL levels,lession proportion,plaque area,circulating EC number,arterial EC apoptosis rate,macrophage(CD68+)and T lymphocyte(CD3+)infiltration areas,TNF-α,monocyte chemoattractant protein-1(MCP-1),vascular cell adhesion molecule-1(VCAM-1),intercellular adhesion molecule-1(ICAM-1),cytoplasm HMGB1,total HMGB1,total RAGE protein levels and nuclear/total p65 NF-κB levels were increased(P<0.05),while nuclear HMGB1 protein,nuclear/total HMGB1 and cytosolic p65 NF-κB levels were decreased(P<0.05).After VERB or simvastatin intervention,arterial lesions were alleviated,TG,TC,LDL levels,lession proportion,plaque area,circulating EC number,arterial EC apoptosis rate,macrophage(CD68+)and T lymphocyte(CD3+)infiltration areas,TNF-α,MCP-1,VCAM-1,ICAM-1,cytoplasm HMGB1,total HMGB1,RAGE protein levels and nuclear/total p65 NF-κB level were decreased(P<0.05),while nuclear HMGB1 protein,nuclear/total HMGB1 and cytosolic p65 NF-κB levels were increased(P<0.05),and HMGB1 was able to antagonize the protective effect of VERB on AS mice.Conclusion:VERB can inhibit expressions of inflammatory and adhesion fac-tors in arterial plaques in ApoE-/-mice,reduce EC shedding and apoptosis,therefore improve AS symptoms in ApoE-/-mice,and the mechanism may be related to the inhibition of HMGB1/RAGE and NF-κB pathway.

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.

Background Per- and polyfluoroalkyl substances (PFAS) are a class of persistent organic pollutants widely used in various products, leading to population exposure and long-term accumulation. At present, there is a lack of research on the relationships between pre-pregnancy PFAS and menstrual characteristics among women undergoing assisted reproductive technology (ART) in China. Objective To explore the relationships between pre-pregnancy PFAS exposure among women undergoing ART and menstrual characteristics prior to assisted reproductive treatment. Methods This study employed a cross-sectional research design, recruiting women undergoing ART treatment at the Reproductive Clinic of the International Peace Maternity & Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, from 2017 to 2020 as study participants. Ultra-high-performance liquid chromatography-tandem mass spectrometry was used to detect 42 types of PFAS in pre-pregnancy serum samples. Questionnaires were administered to collect information on demographic characteristics, lifestyle habits, and menstrual characteristics (average menstrual cycle length, average menstrual period length, menstrual irregularities, and menstrual bleeding volume) of women undergoing ART. Multiple linear regression, binary logistic regression, and multinomial logistic regression analyses were performed to investigate the relationships between individual PFAS exposure before pregnancy and menstrual characteristics among ART women. Additionally, weighted quantile sum (WQS) model was applied to analyze the association between PFAS mixtures and menstrual characteristics. Results In the pre-pregnancy serum samples of the study population, 15 PFAS were detected in more than 60% of the samples, including perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), perfluorododecanoic acid (PFDoDA), perfluorobutanesulfonic acid (PFBS), perfluorohexanesulfonic acid (PFHxS), perfluoroheptanesulfonic acid (PFHpS), perfluorooctanesulfonic acid (PFOS), 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA), 8:2 chlorinated polyfluorinated ether sulfonate (8:2 Cl-PFESA), perfluoro-2-propoxypropanoic acid (HFPO-DA), perfluoro-2-methoxyacetic acid (PFMOAA), and perfluoro-(3,5,7,9,11-pentaoxadodecanoic) acid (PFO5DoDA). Among them, PFOA had the highest median concentration of 9.160 ng·mL⁻¹. The single PFAS exposure analysis revealed a positive correlation between PFAS and irregular menstrual cycles. Specifically, for every natural-log unit (e) increase in PFOA, PFBS, or PFHxS level, the incidence of irregular menstrual cycles increased by 57%, 42%, or 39%, respectively. Most PFAS were positively correlated with the average number of menstrual cycle days, such as PFHpA (b=1.08, 95%CI: 0.11, 2.05), PFOA (b=1.69, 95%CI: 0.39, 3.00), PFBS (b=1.23, 95%CI: 0.25, 2.22), PFHxS (b=1.47, 95%CI: 0.61, 2.32), PFHpS (b=1.48, 95%CI: 0.35, 2.61), and 6:2 Cl-PFESA (b=0.90, 95%CI: 0.08, 1.72). Furthermore, levels of PFHpA (OR=1.39, 95%CI: 1.06, 1.82), PFOA (OR=1.58, 95%CI: 1.09, 2.30), PFBS (OR=1.37, 95%CI: 1.04, 1.80), PFHxS (OR=1.34, 95%CI: 1.05, 1.71), PFHpS (OR=1.53, 95%CI: 1.10, 2.14), and 6:2 Cl-PFESA (OR=1.34, 95%CI: 1.06, 1.70) were positively correlated with low menstrual blood volume, while PFOA (OR=0.40, 95%CI: 0.23, 0.71), PFHpS (OR=0.45, 95%CI: 0.29, 0.71), and HFPO-DA (OR=0.68, 95%CI: 0.48, 0.97) were negatively correlated with high menstrual blood volume. The mixed exposure model showed that PFAS mixtures were positively correlated with the average number of menstrual cycle days (b=1.60, 95%CI: 0.49, 2.71), irregular menstrual cycles (OR=1.77, 95%CI: 1.19, 2.63), and low menstrual blood volume (OR=1.59, 95%CI: 1.08, 2.35), but negatively correlated with high menstrual blood volume (OR=0.40, 95%CI: 0.22, 0.73). Conclusion Women undergoing ART in Shanghai are widely exposed to PFAS prior to conception. Exposure to PFAS before pregnancy may be related to menstrual characteristics among women seeking ART before undergoing fertility treatments, but additional data from larger populations are required to validate the findings of this study.

Objective To evaluate the effectiveness of active screening in improving the detection rate of carbape-nem-resistant Enterobacterales(CRE)in the intensive care units(ICUs).Methods From July 2023 to June 2024,active screening of rectal swab CRE was conducted on ICU patients in 10 hospitals.ICU patients who underwent ac-tive screening from July 2023 to June 2024 were selected as the study group,while those who did not undergo active screening from July 2022 to June 2023 were selected as the control group.Difference in CRE detection rates between the two groups of patients was compared.Results A total of 7 803 ICU patients were included in the study group,744 CRE strains were detected,with a detection rate of 9.53％,out of which 304 CRE strains were detected through routine detection(detection rate 3.90％),3 707 patients underwent active screen,440 CRE strains were detected(detection rate 11.87％).7 561 ICU patients were included in the control group,out of which 250 CRE strains were detected through routine detection,with a detection rate of 3.31％.There was a statistically significant difference in the overall detection rate of CRE between two groups of patients(x2=246.18,P＜0.001).In the study group,CRE detection rate of active screening(11.87％)was higher than that of routine detection(3.90％),with statistically significant difference(x2=264.26,P＜0.001).A total of 17 CRE strains were detected from the study group.The proportions of Klebsiella pneumoniae(80.92％vs 73.41％)and Serratia marcescens(2.30％vs0.23％)in the routine detection group were both higher than in the active screening group,while the proportion of Escherichia coli in the routine detection group was lower(8.22％vs 19.55％),all with statistically significant differences(all P＜0.05).Conclusion The prevalence of CRE in ICUs is relatively high,with a wide range of bac-terial species.Active screening can improve the detection rate of CRE.

Objective:To investigate the effect of verbascoside(VERB)on high-fat diet-induced atherosclerosis(AS)in ApoE-/-mice and the effect on high mobility histone 1(HMGB1)/receptor for glycation end products(RAGE)/nuclear factor κB(NF-κB)pathway.Methods:A total of 90 ApoE-/-mice were randomly divided into normal group,AS group,VERB group,simvastatin group and VERB+pathway activator HMGB1 group,with 18 mice per group.After 8 weeks of group administration,blood and aorta samples were taken.Fasting serum triacylglycerol(TG),total cholesterol(TC)and low density lipoprotein(LDL)levels were deter-mined by automatic biochemical analyzer.Oil red O,HE and TUNEL staining were performed to observe apoptosis of aortic plaque and endothelial cell(EC).Flow cytometry was performed to analyze circulating EC numbers.Immunohistochemistry was performed to analyze the infiltration area of macrophages(CD68+)and T lymphocytes(CD3+)in aortic plaques.Western blot was performed to detect expressions of HMGB1/RAGE/NF-κB pathway,inflammation and adhesion molecules.Results:Compared with normal group,AS group had lipid plaques in arterial intima,thickness of the media was uneven,TG,TC,LDL levels,lession proportion,plaque area,circulating EC number,arterial EC apoptosis rate,macrophage(CD68+)and T lymphocyte(CD3+)infiltration areas,TNF-α,monocyte chemoattractant protein-1(MCP-1),vascular cell adhesion molecule-1(VCAM-1),intercellular adhesion molecule-1(ICAM-1),cytoplasm HMGB1,total HMGB1,total RAGE protein levels and nuclear/total p65 NF-κB levels were increased(P<0.05),while nuclear HMGB1 protein,nuclear/total HMGB1 and cytosolic p65 NF-κB levels were decreased(P<0.05).After VERB or simvastatin intervention,arterial lesions were alleviated,TG,TC,LDL levels,lession proportion,plaque area,circulating EC number,arterial EC apoptosis rate,macrophage(CD68+)and T lymphocyte(CD3+)infiltration areas,TNF-α,MCP-1,VCAM-1,ICAM-1,cytoplasm HMGB1,total HMGB1,RAGE protein levels and nuclear/total p65 NF-κB level were decreased(P<0.05),while nuclear HMGB1 protein,nuclear/total HMGB1 and cytosolic p65 NF-κB levels were increased(P<0.05),and HMGB1 was able to antagonize the protective effect of VERB on AS mice.Conclusion:VERB can inhibit expressions of inflammatory and adhesion fac-tors in arterial plaques in ApoE-/-mice,reduce EC shedding and apoptosis,therefore improve AS symptoms in ApoE-/-mice,and the mechanism may be related to the inhibition of HMGB1/RAGE and NF-κB pathway.

Objective To evaluate the effectiveness of active screening in improving the detection rate of carbape-nem-resistant Enterobacterales(CRE)in the intensive care units(ICUs).Methods From July 2023 to June 2024,active screening of rectal swab CRE was conducted on ICU patients in 10 hospitals.ICU patients who underwent ac-tive screening from July 2023 to June 2024 were selected as the study group,while those who did not undergo active screening from July 2022 to June 2023 were selected as the control group.Difference in CRE detection rates between the two groups of patients was compared.Results A total of 7 803 ICU patients were included in the study group,744 CRE strains were detected,with a detection rate of 9.53％,out of which 304 CRE strains were detected through routine detection(detection rate 3.90％),3 707 patients underwent active screen,440 CRE strains were detected(detection rate 11.87％).7 561 ICU patients were included in the control group,out of which 250 CRE strains were detected through routine detection,with a detection rate of 3.31％.There was a statistically significant difference in the overall detection rate of CRE between two groups of patients(x2=246.18,P＜0.001).In the study group,CRE detection rate of active screening(11.87％)was higher than that of routine detection(3.90％),with statistically significant difference(x2=264.26,P＜0.001).A total of 17 CRE strains were detected from the study group.The proportions of Klebsiella pneumoniae(80.92％vs 73.41％)and Serratia marcescens(2.30％vs0.23％)in the routine detection group were both higher than in the active screening group,while the proportion of Escherichia coli in the routine detection group was lower(8.22％vs 19.55％),all with statistically significant differences(all P＜0.05).Conclusion The prevalence of CRE in ICUs is relatively high,with a wide range of bac-terial species.Active screening can improve the detection rate of CRE.

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.