Effectiveness of calcium ionophore artificial oocyte activation in ART programs for patients with adverse reproductive history: embryological and clinical outcomes

Background. Oocyte competence is a determinant of successful fertilization and embryo development. Poor oocyte quality may lead to fertilization failure or in vitro embryo developmental arrest. Artificial oocyte activation (AOA) using calcium ionophores has been proposed to overcome oocyte activation deficiency in patients with fertilization failure and unsatisfactory embryo quality. The effectiveness of this technology is of interest to fundamental medicine specialists and ART clinics. Aim. To evaluate the effectiveness of calcium ionophore-mediated oocyte activation at the embryological stage of assisted reproductive technology (ART) programs in patients with previous unsuccessful infertility treatments. Materials and Methods. A retrospective cohort comparative study was conducted at the Clinical Hospital "Mother and Child" (Samara) from January to December 2024. Study group (n=35): cycles with AOA using calcium ionophore (A23187, Sigma) after ICSI by medical indications (low fertilization rate in history). Control group (n=61): cycles with standard ICSI procedure without activation. Inclusion criteria: age 18–43 years, partner sperm use, complete data on culture up to day 5. Vitrolife media (Sweden) were used for cell preparation and ICSI. Cells were obtained by transvaginal follicular aspiration 36–37 hours after ovulation trigger. After ICSI, cells were in-cubated in medium with Ca²⁺ ionophore (10 mM concentration) for 8–10 minutes at 6% CO₂, 5% O₂, and +37°C. Embryo quality was assessed using a scoring system based on Gardner et al. (1999) criteria, modified with additional morphological parameters. Results. Main parameters–fertilization rate, cleavage rate, and blastocyst formation rate–showed no significant differences between groups (p>0.05). A significant difference was observed only in mean embryo score at trans-fer (2.91±2.09 vs 3.98±1.41, p=0.008). Clinical pregnancy rate confirmed by ultrasound (36.0% vs 30.4%) and implantation rate (27.3% vs 23.8%) remained comparable (p>0.05). A clinically significant trend toward re-duced difference between positive hCG and clinical pregnancy rate (4% vs 10.7% in control) was revealed, sug-gesting higher embryo competence in the AOA group and reduced early reproductive loss. Conclusion. Calcium ionophore artificial oocyte activation does not lead to statistically significant improvement in main embryological parameters but demonstrates a trend toward reducing the gap between biochemical and clinical pregnancy, which may indicate improved embryo quality in patients with adverse reproductive history. Data accumulation and multicenter randomized studies with increased sample size are required for more reliable conclusions.