Evaluation of Clinical and Oocyte Morphological Parameters Associated With Fertilization Failure in Young Poor Ovarian Response Patients: A Retrospective Case-Control Study

Background: Infertility is a global healthcare problem affecting over 110 million women worldwide, with prevalence continuing to increase. Assisted reproductive technologies (ART) have contributed to improved treatment effectiveness. However, fertilization failure remains a significant concern among women with poor ovarian response. This study aimed to evaluate clinical, hormonal, and oocyte-related factors associated with fertilization failure in young patients with poor ovarian response (POR). Methods: We conducted a retrospective case-control study of 217 women <38 years of age meeting the criteria for POR, divided into two groups. This study was performed at an in vitro fertilization (IVF) center, Kayseri System Hospital, over a 2-year period (January 2022 to December 2023). Data were collected and analyzed using Statistical Package for the Social Sciences (SPSS). Continuous variables (age, body mass index (BMI), hormone levels, and oocyte count) were expressed as mean ± standard deviation (SD) and were compared between groups using independent-samples t-tests. Categorical data (oocyte morphological abnormalities) were reported as frequencies and percentages and were compared using chi-square tests. All patients underwent intracytoplasmic sperm injection (ICSI) cycles. Results: The study found no significant differences in age, BMI, or baseline hormone levels between groups. However, women with fertilization failure had significantly lower levels of estradiol (E2) upon human chorionic gonadotropin (hCG) trigger (631.0 ± 582.6 vs. 798.9 ± 535.3 pg/mL, p = 0.03), fewer cumulus–oocyte complexes (2.1 ± 2.1 vs. 3.5 ± 2.1, p < 0.001), and fewer mature (metaphase II) oocytes (1.2 ± 0.5 vs. 2.3 ± 0.7, p < 0.001). Morphological analysis revealed that smooth endoplasmic reticulum (SER) clusters were more frequent in the fertilization failure group (21% vs. 5%, p = 0.0003). Multivariable logistic regression analysis demonstrated that lower anti-Müllerian hormone (AMH) levels, higher baseline follicle-stimulating hormone (FSH) levels, higher total gonadotropin dose, and longer infertility duration were independently associated with fertilization failure after adjustment for potential confounding factors. Conclusions: Fertilization failure was positively associated with lower E2 levels on the day of hCG trigger, reduced oocyte yield, and a greater prevalence of SER clusters. Among young POR patients, SER clusters may represent the most frequently observed oocyte morphological abnormality associated with fertilization failure.