Predictors of Ovarian Sensitivity Index in Controlled Ovarian Stimulation: A Retrospective Cohort Study

Background: This study evaluated the ovarian sensitivity index (OSI) among women undergoing controlled ovarian stimulation (COS) and identified the key predictors, including age, anti-Müllerian hormone (AMH), and antral follicle count (AFC). Materials and Methods: A retrospective analysis of 135 women who met the eligibility criteria undergoing COS was conducted in a fertility clinic in South West Nigeria over 4 years, September 2021 to August 2025. Socio-demographic data, ovarian reserve markers, number of oocytes retrieved (germinal vesicle, M1, and M2), and OSI values were assessed. Multiple regression and receiver operating characteristic (ROC) analysis were used to identify predictors of OSI. Results: The mean age was 36.9 ± 4.5 years, with most women aged 35–39 years (44%). Normal AFC values were observed in 57.8%, whereas 36.3% demonstrated low ovarian reserve. The mean OSI was 46.0 ± 33.5. Regression analysis showed that age ( P = 0.032) and AFC ( P < 0.001) were significant predictors of OSI, whereas AMH was not significant. ROC analysis revealed that higher AMH values were associated with greater ovarian response. Conclusion: AFC and age remained strong predictors of ovarian sensitivity during COS, whereas AMH showed limited predictive value in this cohort. These findings may guide individualised stimulation strategies in in vitro fertilization cycles.