Objective:To investigate the influence of inner cell mass and trophectoderm cytoplasmic strings during blastocyst expan-sion on embryonic development and pregnancy outcome.Methods:A retrospective cohort analysis was performed for the clinical data of patients who received pre-implantation genetic testing for aneuploidy(PGT-A)and underwent single blastocyst transplantation in our hospital from June 2019 to December 2021.A total of 530 patients were enrolled,and genetic testing was performed for 2132 blasto-cysts.According to the presence or absence of cytoplasmic strings during blastocyst expansion,the blastocysts were divided into cyto-plasmic strings(+)group with 534 blastocysts and cytoplasmic strings(-)group with 1598 blastocysts,and quality and PGT-A results were compared between the two groups.After the transfer of euploid blastocysts,pregnancy outcome was compared between the 115 blastocysts with cytoplasmic strings and the 415 blastocysts without cytoplasmic strings.Results:The rates of cytoplasmic strings(+)in the high-,average-,and low-quality blastocyst groups were 30.19%,24.62%,and 12.63%,respectively.The correlation analysis showed a correlation coefficient of-0.115(P<0.001)between embryo quality and the rate of cytoplasmic strings(+).There was no sig-nificant difference in euploidy rate between the two groups(45.3%vs.44.6%).There were no significant differences between the euploid blastocysts with cytoplasmic strings and those without cytoplasmic strings in implantation rate(72.17%vs.66.02%,P=0.213),miscarriage rate(14.46%vs.12.77%,P=0.691),and live birth rate(61.74%vs.57.59%,P=0.424).Conclusion:The presence of cyto-plasmic strings is associated with the morphological quality of blas-tocysts,while it has no impact on embryo ploidy or clinical outcome after euploid embryo transfer.Further research is needed to confirm the impact of cytoplasmic strings on embryonic development.

Artificial intelligence (AI) technology is expected to assist physicians in improving the accuracy and efficiency of embryo assessment. However, embryo development is a continuous and dynamic process, when is meaningful or the whole development process need to be considered? Some research teams use static image analysis, which loses much important information, and others utilize algorithm-driven applications of "black-box" models to analyse embryo videos, which have limited their interpretability or explainability. Machine learning or deep learning is prone to abused due to its inherent complexity, and in order to apply AI more accurately, this paper discusses the clinical implications of algorithmic interpretations of AI in human embryo ploidy prediction.

The principle of informed consent is one of the most important principles in the ethical principles of human assisted reproductive technology (ART), and ART can only be performed after both spouses have voluntarily agreed and signed a written informed consent form, which is also an important measure to protect the interests of both doctors and patients. The signing of the ART informed consent form not only involves more ethical issues, but also requires the incorporation of a lot of specific considerations. This paper analyzes the development of ART informed consent, the ethical issues involved, and the considerations that need to be taken into account when signing the consent form, with the aim of promoting the further standardization and improvement of ART informed consent, and helping the development of ART.

Objective:To evaluate the effect of prolonged cryopreservation duration of high-quality embryos on clinical outcomes.Methods:A retrospective cohort study was conducted, analyzing 8 988 frozen-thawed embryo transfer cycles performed from January 2016 to December 2023 at the Center for Reproductive Medicine, Chongqing Maternal and Child Healthcare Hospital where patients underwent endometrial preparation with artificial cycles and subsequent transfer of high-quality embryos. Embryos were divided into four groups according to the length of time they had been cryopreserved: ≤3-month group ( n=3 030), 4-6-month group ( n=3 193), 7-12-month group ( n=1 465), and >12-month group ( n=1 300). High-quality cleavage-stage embryos and blastocysts were selected according to the Istanbul Consensus and Gardner grading system. High-quality cleavage-stage embryos were defined as those graded ≤2, while high-quality blastocysts were defined as those graded ≥4BB. Generalized estimating equations were employed for multivariate analysis. Primary outcome indicator was clinical pregnancy rate, with secondary outcome indicators comprising live birth rate, miscarriage rate and preterm birth rate. Results:Significant intergroup differences were observed in baseline characteristics, including age, body mass index, anti-Müllerian hormone levels, fertilization method, endometrial thickness on transfer day, infertility etiology, infertility type, number of embryos transferred, embryo culture duration, number of eggs obtained, and preimplantation genetic testing (all P<0.05). Clinical pregnancy rates for the ≤3-month, 4-6-month, 7-12-month, and >12-month groups were 69.04% (2 092/3 030), 70.15% (2 240/3 193), 61.16% (896/1 465), and 57.69% (750/1 300), respectively, and live birth rates were 58.58% (1 775/3 030), 60.04% (1 917/3 193), 51.40% (753/1 465), and 47.00% (611/1 300), with significantly differences (all P<0.001). After adjusting for confounders via multivariate analysis, the 4-6-month group showed no statistically significant difference in clinical pregnancy rate or live birth rate compared with the ≤3-month group (clinical pregnancy: OR=0.982, 95% CI: 0.874-1.103, P=0.754; live birth: OR=0.989, 95% CI: 0.887-1.102, P=0.835). However, both the 7-12-month group (clinical pregnancy: OR=0.772, 95% CI: 0.671-0.888, P<0.001; live birth: OR=0.805, 95% CI: 0.704-0.921, P=0.002) and >12-month group (clinical pregnancy: OR=0.765, 95% CI: 0.662-0.885, P<0.001; live birth: OR=0.772, 95% CI: 0.671-0.888, P<0.001) exhibited significant decreases in clinical pregnancy rate and live birth rate. No significant differences were observed in miscarriage rate and preterm birth rate among the four groups (all P>0.05). Stratified by age, the results were consistent with the total population. Conclusion:The duration of high-quality embryo vitrification freezing exceeding 6 months is negatively correlated with clinical pregnancy rate and live birth rate, and cryostorage time should be considered as a relevant factor in embryo selection.

Artificial intelligence (AI) technology is expected to assist physicians in improving the accuracy and efficiency of embryo assessment. However, embryo development is a continuous and dynamic process, when is meaningful or the whole development process need to be considered? Some research teams use static image analysis, which loses much important information, and others utilize algorithm-driven applications of "black-box" models to analyse embryo videos, which have limited their interpretability or explainability. Machine learning or deep learning is prone to abused due to its inherent complexity, and in order to apply AI more accurately, this paper discusses the clinical implications of algorithmic interpretations of AI in human embryo ploidy prediction.

The principle of informed consent is one of the most important principles in the ethical principles of human assisted reproductive technology (ART), and ART can only be performed after both spouses have voluntarily agreed and signed a written informed consent form, which is also an important measure to protect the interests of both doctors and patients. The signing of the ART informed consent form not only involves more ethical issues, but also requires the incorporation of a lot of specific considerations. This paper analyzes the development of ART informed consent, the ethical issues involved, and the considerations that need to be taken into account when signing the consent form, with the aim of promoting the further standardization and improvement of ART informed consent, and helping the development of ART.

Objective:To evaluate the effect of prolonged cryopreservation duration of high-quality embryos on clinical outcomes.Methods:A retrospective cohort study was conducted, analyzing 8 988 frozen-thawed embryo transfer cycles performed from January 2016 to December 2023 at the Center for Reproductive Medicine, Chongqing Maternal and Child Healthcare Hospital where patients underwent endometrial preparation with artificial cycles and subsequent transfer of high-quality embryos. Embryos were divided into four groups according to the length of time they had been cryopreserved: ≤3-month group ( n=3 030), 4-6-month group ( n=3 193), 7-12-month group ( n=1 465), and >12-month group ( n=1 300). High-quality cleavage-stage embryos and blastocysts were selected according to the Istanbul Consensus and Gardner grading system. High-quality cleavage-stage embryos were defined as those graded ≤2, while high-quality blastocysts were defined as those graded ≥4BB. Generalized estimating equations were employed for multivariate analysis. Primary outcome indicator was clinical pregnancy rate, with secondary outcome indicators comprising live birth rate, miscarriage rate and preterm birth rate. Results:Significant intergroup differences were observed in baseline characteristics, including age, body mass index, anti-Müllerian hormone levels, fertilization method, endometrial thickness on transfer day, infertility etiology, infertility type, number of embryos transferred, embryo culture duration, number of eggs obtained, and preimplantation genetic testing (all P<0.05). Clinical pregnancy rates for the ≤3-month, 4-6-month, 7-12-month, and >12-month groups were 69.04% (2 092/3 030), 70.15% (2 240/3 193), 61.16% (896/1 465), and 57.69% (750/1 300), respectively, and live birth rates were 58.58% (1 775/3 030), 60.04% (1 917/3 193), 51.40% (753/1 465), and 47.00% (611/1 300), with significantly differences (all P<0.001). After adjusting for confounders via multivariate analysis, the 4-6-month group showed no statistically significant difference in clinical pregnancy rate or live birth rate compared with the ≤3-month group (clinical pregnancy: OR=0.982, 95% CI: 0.874-1.103, P=0.754; live birth: OR=0.989, 95% CI: 0.887-1.102, P=0.835). However, both the 7-12-month group (clinical pregnancy: OR=0.772, 95% CI: 0.671-0.888, P<0.001; live birth: OR=0.805, 95% CI: 0.704-0.921, P=0.002) and >12-month group (clinical pregnancy: OR=0.765, 95% CI: 0.662-0.885, P<0.001; live birth: OR=0.772, 95% CI: 0.671-0.888, P<0.001) exhibited significant decreases in clinical pregnancy rate and live birth rate. No significant differences were observed in miscarriage rate and preterm birth rate among the four groups (all P>0.05). Stratified by age, the results were consistent with the total population. Conclusion:The duration of high-quality embryo vitrification freezing exceeding 6 months is negatively correlated with clinical pregnancy rate and live birth rate, and cryostorage time should be considered as a relevant factor in embryo selection.

BACKGROUND:In recent years,the demand for in vitro maturation of immature oocytes has increased.Oocyte maturation is affected by many factors,among which the selection of medium is particularly important,and there is currently no unified plan. OBJECTIVE:To compare the in vitro maturation of germinal vesicle stage oocytes with different maturation media and to investigate its effects on oocyte quality and developmental potential. METHODS:Germinal vesicle oocytes were matured in G-1TM PLUS medium,CZB medium and M16 medium,and mature oocytes in vivo were used as control group to compare in vitro fertilization and early embryo development among various groups.The immunofluorescence method was used to evaluate mitochondrial function in mature oocytes of each group.Calcium oscillation was detected by confocal microscopy real-time imaging system. RESULTS AND CONCLUSION:(1)There was no significant difference in the first polar body ejection rate among the three groups(P>0.05).(2)The rate of in vitro fertilization was higher in the G-1TM PLUS group(52.86±11.24)%than that in the M16 group(37.76±6.70)%and the CZB group(30.62±5.51)%.The blastocyst rate was lower in the CZB group(36.23±6.63)%than that in the control group(78.16±4.17)%,G-1TM PLUS group(55.75±7.63)%and M16 group(53.36±6.33)%.(3)Compared with the control group,the length-to-width ratio of the spindle in the CZB group increased(P<0.005).(4)The mitochondrial function of the CZB group was worse than that of the control group,G-1TM PLUS group and M16 group,and abnormal mitochondrial agglutination occurred in the CZB group.(5)The frequency of calcium oscillations in the CZB and M16 groups was significantly higher than that in the G1 and control groups.In conclusion,during in vitro maturation of mouse oocytes,in vitro maturation rate was not significantly different among G-1TM PLUS,CZB and M16 media,but the G-1TM PLUS medium had a higher rate of fertilization and blastocyst formation.

BACKGROUND:Superovulation is a common therapy in assisted reproductive technology.In clinical practice,some patients experience repeated superovulation to get pregnant. OBJECTIVE:To explore the effect of repeated superovulation on the developmental potential of oocytes in mice and humans. METHODS:Both animal experiments and retrospective clinical research were conducted.The animal study involved 90 SPF grade ICR 8-week-old female mice,who were randomly divided into three groups for 1,3,and 5 superovulations,respectively.The clinical study involved 306 patients who had undergone three consecutive in vitro fertilization cycles.The number of ovules obtained and embryonic development in different cycles were compared. RESULTS AND CONCLUSION:(1)The animal study indicated that repeated superovulation did not affect the embryonic development or developmental speed of mouse embryos.Similarly,there was no significant difference in the mouse blastocyst apoptosis,DNA damage,or the formation of inner cell mass and trophectoderm(P>0.05).(2)The clinical study also revealed no significant differences in the number of retrieved oocytes(8.60±5.04,8.58±4.87,and 8.38±4.63,P=0.81)and transferable embryos(2.42±1.99,2.40±1.92,and 2.64±2.00,P=0.26)over the three cycles.(3)In both the young group(<35 years)and the old group(≥35 years),the embryo quality was not affected by repeated superovulation(P>0.05).(4)These findings show that repeated superovulation does not affect the developmental potential of oocytes in mice and humans.

Objective:To explore the correlation between blastomere count variations “skip value” which extracted from by time-lapse technology (TLT) combined with artificial intelligence (AI) and morphological features of in vitro fertilization (IVF) embryo, and to test its feasibility in clinical applications.Methods:This study was a diagnostic experiment (AI reassessment of embryo transferred patients), a total of 6 545 embryos from 1 226 patients who underwent IVF at the Women and Children′s Hospital of Chongqing Medical University from December 2020 to December 2021 were retrospectively analyzed, of which 2 869 embryos were attempted to cultured to blastocyst stage by TLT. The embryo dynamic map (EDM) was drawn by Embryo Viewer, a TLT recording software, based on embryo developmental kinetics. The self-developed AI embryo evaluation software identified and recorded the number of cleavages in real time during embryonic development, and compared with the EDM, the correlation between the skip value formed by the change of cleavage sphere counts and the outcomes of the embryos was analyzed. The correlation among skip value, morphological score of embryo, implantation rate and live birth rate were performed by Spearman and step-up logistic regression. The receiver operating characteristic (ROC) curve was selected for reporting there relationship of skip value and morphology. Finally, predicting power of skip value for implantation and live birth rate were performed by ROC analysis.Results:The total skip values extracted from the blastomere count of embryos (72 hours post-fertilization) were negatively correlated with abnormal cleavage, blastocyst formation rate, day 3 (D3)-cell score, uneven size and fragmentation (the β values were -0.268, -0.116, -0.213, -0.159 and -0.222, respectively; all P<0.001); positively correlated with D3-cell number ( β=0.034; P<0.001); negatively correlated with blastocyst formation rate and implantation rate ( OR=0.97, 95% CI: 0.93-0.99, P=0.034; OR=0.96, 95% CI: 0.93-0.98, P=0.044). The power of predicting implantation were similar between the order selection of skip values and traditional morphology criteria [area under curve (AUC): 0.679 vs 0.620]. Live birth rate were negatively correlated with female age ( OR=0.91, 95% CI: 0.88-0.93; P<0.001), D3 general score ( OR=0.77, 95% CI: 0.59-0.99; P=0.045) and order selection of skip values ( OR=0.98, 95% CI: 0.96-0.99; P=0.038), while positively correlated with retrieved oocyte number and endometrial thickness in embryo transferred ( OR=1.08, 95% CI:1.05-1.11, P<0.001; OR=1.09, 95% CI:1.06-0.12, P<0.001, respectively) from multivariate regression analysis, and the power of predicting live birth was 0.666 for AUC. Conclusions:The skip value and its order form is a systematic quantification of embryo development, correlated with embryo developmental quality and clinical outcome. It could be an addition parameter for embryo culture and selection.