Predictive Performance of Oocyte Count for Clinical Pregnancy in GnRH Antagonist IVF Cycles: A Multivariable Analysis...

Background and Objectives: The optimal oocyte yield in gonadotropin-releasing hormone (GnRH) antagonist in vitro fertilization (IVF) cycles remains debated, and data specific to antagonist protocols are limited. This study evaluated the discriminative and independent predictive performance of oocyte count for clinical pregnancy in GnRH antagonist IVF cycles. Materials and Methods: This retrospective cohort included 1171 women undergoing their first GnRH antagonist IVF cycle with fresh embryo transfer at a single tertiary center (September 2007-December 2021). The primary outcome was an institutional composite pregnancy outcome (sustained β-hCG positivity with subsequent ongoing intrauterine pregnancy or live birth; biochemical and ectopic pregnancies were negative). Patients were grouped by oocytes retrieved (1-5, 6-10, 11-15, ≥16). Performance was assessed with logistic regression, ROC with 2000-iteration bootstrap, integrated discrimination improvement (IDI), continuous net reclassification improvement (NRI), and restricted cubic spline. Predefined subgroup analyses by age, regimen, and antral follicle count tertile were performed. Results: A positive outcome occurred in 430 patients (36.7%). After adjustment, oocyte count was not an independent predictor (adjusted odds ratio 0.999, 95% CI 0.979-1.020; p = 0.96). The full model (AUC 0.564, 95% CI 0.529-0.598) did not outperform oocyte count alone (AUC 0.532; bootstrap p = 0.11). IDI (0.011) and NRI (0.135) were statistically detectable but clinically trivial. Spline regression showed no non-linearity (p = 0.47). Findings were consistent across subgroups, and the narrow confidence interval excluded per-oocyte effects ≥1.10. Conclusions: In GnRH antagonist IVF cycles, oocyte count showed weak discriminatory performance and was not independently associated with fresh-cycle pregnancy. Oocyte yield should be interpreted alongside-rather than as a substitute for-established parameters such as age and ovarian reserve. The principal clinical value of a higher oocyte response may lie in cumulative rather than fresh-cycle success. Live-birth outcomes were not available, and the source institution was permanently closed in 2025; these limitations define the boundary of inference.