Characteristics and Outcomes of Donor Oocyte Cycles: Factors Associated with Success Short title: Donor Oocyte Cycles: Factors Associated with Success

Background & Objective: The use of donor oocytes has gained significant popularity worldwide. A primary indication for using donor oocytes is primary ovarian insufficiency. This research aimed to describe the characteristics of donor oocyte cycles and to assess factors that may influence clinical pregnancies and live birth outcomes. Materials & Methods: This retrospective study was conducted on 81 recipients who underwent embryo transfer following oocyte donation at Infertility Department, Da Nang Hospital for Women and Children from January 2021 to December 2024. These patients were indicated for oocyte donation due to primary ovarian insufficiency, diminished ovarian reserve, repeated IVF failures (attributable to poor oocyte quality), or genetic disorders (Noonan Syndrome, Kallmann Syndrome, Fragile X Syndrome…). Results: The mean age of recipients and donors was 37.98±5.09 years and 29.13±3.98 years, respectively. Diminished ovarian reserve was the primary reason for oocyte donation, accounting for 56.8% of cases. On average, 16.43±6.37 oocytes were retrieved per donor. The positive beta-hCG rate was 45.68%. Among the analyzed cycles, 39.51 % resulted in clinical pregnancies, and 32.10% culminated in live births. Recipients who attained gestation were significantly younger compared with those without pregnancy outcomes (37.1±5.3 years vs 41.2±5.2 years, P=0.037). There were no significant differences for other parameters, including BMI, endometrial lining, or the reason for oocyte donation. Conclusion: The patient’s age greatly contributes in achieving the best possible outcome in cycles using donor oocytes. Further research is needed to explore additional prognostic factors, including donor characteristics, male infertility parameters, and embryo quality, to refine treatment strategies and optimize outcomes in donor oocyte IVF programs.