Patients using progesterone and GnRH antagonists during ovarian stimulation comparison of differences between oocyte morphologies

Objective: The aim of this study is to retrospectively compare the effects of GnRH antagonists and dydrogesterone on oocyte morphology during ovarian stimulation. Materials and Methods: The study included a total of 106 patients aged 24-44 who applied to the Selçuk University Faculty of Medicine In Vitro Fertilization (IVF) Center between January 2021 and June 2023. Of these, 71 patients were treated with GnRH antagonists, and 35 patients were treated with dydrogesterone. Baseline FSH, LH, estradiol, and AMH levels were recorded, and oocyte morphological characteristics were evaluated based on embryologist reports following oocyte pick-up (OPU). Statistical analyses were performed using IBM SPSS 27 software. Independent samples t-test was used for normally distributed data, Mann-Whitney U test for non-normally distributed data, and Chi-square/Fisher's exact test for categorical data. Results were considered significant at p<0.05 and evaluated within a 95% confidence interval. Results: The rate of oocytes with normal morphology was significantly higher in the GnRH antagonist group (1.4±1.4) compared to the dydrogesterone group (0.5±1.2; p=0.002). In contrast, cytoplasmic granulation (2.3±1.8 vs. 1.0±1.4; p<0.001) and irregular perivitelline space (8.6% vs. 2.8%; p=0.189) were more frequently observed in the dydrogesterone group. There was no significant difference between the groups in terms of total oocyte count (7.2±4.5 vs. 8.6±6.9), germinal vesicle stage (0.8±1.0 vs. 0.9±1.6), or metaphase II stage (6.0±4.0 vs. 7.1±5.3). Zona pellucida thickness, empty zona, or fractured zona incidence were similar between the groups. The negative correlation between AMH and age (r=-0.404; p=0.003) confirmed that ovarian reserve decreases with age. Conclusion: The findings suggest that GnRH antagonists may be more advantageous than dydrogesterone in preserving oocyte morphology. The increased incidence of cytoplasmic granulation and irregular perivitelline space in the dydrogesterone group indicates that this protocol may affect cytoplasmic maturation processes. However, the similarities in total oocyte yield and maturity stages suggest that both protocols are acceptable in terms of stimulation efficacy. In clinical practice, GnRH antagonists may be an option, especially for patients with a history of recurrent implantation failure or cytoplasmic anomalies.