Abstract
PURPOSE: To evaluate how the timing of oocyte denudation (DN) and intracytoplasmic sperm injection (ICSI) affects embryological and clinical outcomes in highly standardized oocyte donation cycles. METHODS: This retrospective cohort study included 1538 donor stimulation cycles from a single IVF center between January 2019 and July 2023. Timing intervals between human chorionic gonadotropin (hCG) administration, oocyte pick-up (OPU), DN, and ICSI were recorded. Outcomes included oocyte maturation (MII rate), fertilization, embryo quality, and clinical results. Statistical analyses included linear and logistic regression models, and chi-square tests, adjusting for donor and recipient age and BMI. RESULTS: Longer hCG-DN intervals (> 39 h) were significantly associated with increased MII rates and decreased proportions of MI and discarded oocytes (P < 0.05). However, hCG-DN timing had no effect on fertilization rates, embryo quality, or pregnancy outcomes. Shorter DN-ICSI intervals (< 90 min) were associated with a higher proportion of top-quality blastocysts and fewer medium-quality embryos (P < 0.05). DN-ICSI timing did not influence clinical outcomes. Recipient BMI was the strongest predictor of pregnancy, clinical pregnancy, and live birth (P < 0.001). CONCLUSIONS: Extended incubation prior to denudation improves oocyte maturation but does not affect fertilization or pregnancy. Short DN-ICSI intervals favor top-quality blastocyst formation without altering clinical results. Recipient BMI significantly impacts reproductive success. These findings support timing optimization in ART and highlight the influence of patient-specific factors.