The Estradiol-to-Oocyte ratio as a predictor of ART outcomes: evidence and implications in PCOS

INTRODUCTION: Polycystic ovary syndrome (PCOS) is an endocrine disease involving reproductive dysfunction, with anovulation and diminished oocyte quality, and is related to endometrial dysfunction. Estradiol-to-oocyte ratio (EOR) surfaced as a measure of success in reproductive effects in PCOS during assisted reproductive technical expertise. AREAS COVERED: This review provides a comprehensive summary of current evidence on EOR, its physiological significance, relationship with oocyte maturation, and impact on embryo viability in IVF. We will explore molecular mechanisms of EOR's action in follicular development, integrating data from imaging technologies and biomarker studies. It also discusses its clinical utility in optimizing individualized fertility treatment and improving reproductive prognoses for PCOS patients during IVF. EXPERT OPINION: EOR may empower IVF specialists by enabling more refined assessments, helping them make more personalized and confident treatment decisions for patients (embryo transfer and subsequent cycle protocol). It provides guidance for treatment adjustments in subsequent cycles, especially when prior responses were high in quantity but suboptimal in quality. Incorporating EOR into clinical practice complements clinical expertise and supports the balance between efficacy and safety in managing PCOS-related infertility.