Objective:To investigate the effects of individual versus connected microdroplet culture modes in time-lapse (TL) incubators on embryo development parameters and pregnancy outcomes in patients undergoing whole embryo culture to blastocyst stage.Methods:Using a retrospective cohort study, clinical data from 3 507 fresh blastocyst transfer cycles were analyzed. These cycles involved patients who underwent assisted reproductive technology treatment with whole embryo culture to blastocyst stage at the Reproductive Medical Center of Northwest Women's and Children's Hospital between January 2019 and December 2023. Based on different culture modes, patients were divided into two groups, connected group ( n=2 446, using connected microdroplet culture) and individual group ( n=1 061, using individual microdroplet culture). Baseline characteristics, embryo development parameters, pregnancy outcomes, and neonatal outcomes were compared between the two groups. Generalized linear models (GLM) were used to adjust for confounding factors and analyze the effect of culture mode. Results:Embryo development assessment showed the day 3 (D3) high-quality embryo rate in the connected group [60.12% (12 136/20 187)] was significantly lower than that in the individual group [63.62% (4 705/7 395), P<0.001], whereas the high-quality blastocyst formation rate [34.93% (7 052/20 187)] and the available blastocyst formation rate [56.07% (11 319/20 187)] were both significantly higher than those in the individual group [33.08% (2 446/7 395), P=0.004; 51.45% (3 805/7 395), P<0.001], with statistically significant differences. The implantation rate [67.40% (1 774/2 632)], the clinical pregnancy rate [70.20% (1 717/2 446)], and the live birth rate [60.66% (1 469/2 446)] in the connected group were all significantly higher than those in the individual group [63.40% (724/1 142), P=0.017; 66.73% (708/1 061), P=0.041; 55.89% (593/1 061), P=0.021], with statistically significant differences. Neonatal outcomes showed no statistically significant difference between the two groups (all P>0.05). After adjusting for confounding factors using GLM, connected culture was an independent influencing factor for D3 high-quality embryo rate (a MD=-0.017, 95% CI: -0.034-0.000, P=0.046), high-quality blastocyst formation rate (a MD=-0.020, 95% CI: 0.002-0.037, P=0.026), available blastocyst formation rate (a MD=0.032, 95% CI: 0.015-0.048, P<0.001), live birth rate (a OR=1.182, 95% CI: 1.006-1.388, P=0.042). However, it had no effect on D3 available embryo rate, clinical pregnancy rate, or early miscarriage rate (all P>0.05). Conclusion:In TL incubator systems, individual and connected microdroplet culture modes exert different effects at various stages of embryo development. Individual microdroplet culture can significantly enhance cleavage-stage embryo quality, whereas the connected microdroplet culture was more beneficial for enhancing the blastocyst formation rate and quality, ultimately improving the live birth rate without increasing neonatal risks.

Objective:To investigate the effects of individual versus connected microdroplet culture modes in time-lapse (TL) incubators on embryo development parameters and pregnancy outcomes in patients undergoing whole embryo culture to blastocyst stage.Methods:Using a retrospective cohort study, clinical data from 3 507 fresh blastocyst transfer cycles were analyzed. These cycles involved patients who underwent assisted reproductive technology treatment with whole embryo culture to blastocyst stage at the Reproductive Medical Center of Northwest Women's and Children's Hospital between January 2019 and December 2023. Based on different culture modes, patients were divided into two groups, connected group ( n=2 446, using connected microdroplet culture) and individual group ( n=1 061, using individual microdroplet culture). Baseline characteristics, embryo development parameters, pregnancy outcomes, and neonatal outcomes were compared between the two groups. Generalized linear models (GLM) were used to adjust for confounding factors and analyze the effect of culture mode. Results:Embryo development assessment showed the day 3 (D3) high-quality embryo rate in the connected group [60.12% (12 136/20 187)] was significantly lower than that in the individual group [63.62% (4 705/7 395), P<0.001], whereas the high-quality blastocyst formation rate [34.93% (7 052/20 187)] and the available blastocyst formation rate [56.07% (11 319/20 187)] were both significantly higher than those in the individual group [33.08% (2 446/7 395), P=0.004; 51.45% (3 805/7 395), P<0.001], with statistically significant differences. The implantation rate [67.40% (1 774/2 632)], the clinical pregnancy rate [70.20% (1 717/2 446)], and the live birth rate [60.66% (1 469/2 446)] in the connected group were all significantly higher than those in the individual group [63.40% (724/1 142), P=0.017; 66.73% (708/1 061), P=0.041; 55.89% (593/1 061), P=0.021], with statistically significant differences. Neonatal outcomes showed no statistically significant difference between the two groups (all P>0.05). After adjusting for confounding factors using GLM, connected culture was an independent influencing factor for D3 high-quality embryo rate (a MD=-0.017, 95% CI: -0.034-0.000, P=0.046), high-quality blastocyst formation rate (a MD=-0.020, 95% CI: 0.002-0.037, P=0.026), available blastocyst formation rate (a MD=0.032, 95% CI: 0.015-0.048, P<0.001), live birth rate (a OR=1.182, 95% CI: 1.006-1.388, P=0.042). However, it had no effect on D3 available embryo rate, clinical pregnancy rate, or early miscarriage rate (all P>0.05). Conclusion:In TL incubator systems, individual and connected microdroplet culture modes exert different effects at various stages of embryo development. Individual microdroplet culture can significantly enhance cleavage-stage embryo quality, whereas the connected microdroplet culture was more beneficial for enhancing the blastocyst formation rate and quality, ultimately improving the live birth rate without increasing neonatal risks.