JBRA Assist. Reprod. 2025;29(Suppl 1):6-6
ORAL PRESENTATION
doi: 10.5935/1518-0557.20250064
1Instituto Ideia Fértil
Objective: The optimization of in vitro embryo culture conditions is critical for improving assisted reproduction outcomes. While continuous culture systems simulate the in vivo environment more closely, the practice of renewing culture media remains common, aiming to reduce metabolic waste such as ammonia. However, there is debate regarding whether this intervention is beneficial in systems designed for uninterrupted culture. This study investigates the effects of media renewal in continuous culture on embryo development and quality.
Methods: This retrospective study included patients undergoing assisted reproduction treatments between April 2023 and February 2025. Oocytes from fresh or warmed cycles were fertilized via ICSI and maintained in continuous culture medium (Global®, LifeGlobal) within a tri-gas incubator set to 37°C, 7.5% CO₂, and pH 7.25-7.3. Only cases with >10 embryos on D3 were included. On D3, embryos from each patient were randomly allocated into two groups:
-Group 1: Embryos continued in uninterrupted culture.
-Group 2: Embryos had the culture medium renewed. Embryo development was monitored on D5, D6, and D7. The primary outcomes were the total number of blastocysts formed and the proportion of top-quality blastocysts. Data were analyzed using Jamovi 2.6. The Wilcoxon test was applied to assess statistical significance, with p = 0.05 considered significant.
Results: A total of 186 patients (mean age: 35 years) were included, yielding 3,066 oocytes and 2,076 embryos by D3. Of the resulting blastocysts, 58.1% belonged to Group 1, and 41.0% to Group 2 (p < 0.001). Median blastocyst formation rates per patient were also higher in Group 1 (25th percentile: 50.0 vs. 31.3; 75th percentile: 67.8 vs. 50.0). The average number of blastocysts per patient was 5.42 in Group 1 and 3.65 in Group 2 (p < 0.001). Group 1 also had a higher percentage of top-quality blastocysts: - D5: 58.1% vs. 41.9%- D6: 58.5% vs. 41.5%- D7: 90.5% vs. 9.5%.
Conclusion: Biggers & Racowsky (2002) demonstrated the potential of uninterrupted culture protocols in supporting human embryo development to the blastocyst stage. Reed et al. (2009) similarly reported superior outcomes with continuous media compared to sequential protocols. These findings support the concept that modern media are formulated to meet the metabolic needs of embryos throughout preimplantation development.Despite the rationale for media renewal to reduce toxic by-products like ammonia (Visek, 1968), our results indicate a detrimental effect of media exchange in continuous systems. Specifically, uninterrupted culture yielded 20% more blastocysts and significantly higher top-quality embryo rates on all assessed days, particularly D7, where the improvement reached 90%. Environmental factors such as temperature shifts, light exposure, and fluctuations in pH or osmolarity during manipulation may negatively affect embryo viability by increasing oxidative stress (Agarwal et al., 2022). Additionally, uninterrupted culture may allow for the accumulation of beneficial autocrine/paracrine factors, contributing to improved outcomes. Moreover, such protocols streamline lab workflow, reducing costs and handling (Biggers & Summers, 2008). These findings reinforce the advantages of minimizing disturbances to the embryo culture environment, particularly in systems designed for continuous use. Conclusion:Media renewal on D3 in continuous culture media negatively affected blastocyst development and embryo quality. Continuous, uninterrupted culture supports superior outcomes and may be considered the preferred approach in IVF laboratory protocols.
References
Agarwal et al. Antioxidants . 2022;11:477.
Biggers, Racowsky. Reprod Biomed Online. 2002;5:133-40.
Biggers, Summer. Fertil Steril. 2008;90:473-83.