Predictive Value and Optimal Threshold of Follicle Size in IVF: Systematic Review and Multiple‐Threshold Meta‐Analysis

ABSTRACT Background Follicle size was generally monitored during controlled ovarian stimulation, yet its predictive value for oocyte developmental potential and the discriminating threshold is debated. Objectives To explore the predictive value of follicle size for oocyte developmental competency and establish the corresponding optimal threshold. Search Strategy We searched PubMed, Web of Science, EMBASE and Cochrane Library up to February 29th, 2024. Selection Criteria Included studies investigated the association between follicle size and oocyte developmental competency in IVF treatments. Data Collection and Analysis Data extraction followed the Cochrane Handbook. A multiple‐threshold meta‐analysis and standard bivariate meta‐analysis were used. Main Results This meta‐analysis included 14 studies comprising 25 528 follicles. Results showed follicle size is predictive for oocyte developmental competence, including oocyte maturity (area under the receiver operation characteristic curve [AUC]: 0.72, 95% confidence interval 0.66–0.77; n = 24 116; follicle size ≥ 15 mm), normal fertilisation (0.62, 0.55–0.69; n = 25 321; follicle size ≥ 16 mm), blastocyst formation (0.61, 0.53–0.69; n = 12 859; follicle size ≥ 15 mm) and good‐quality embryo (0.64, 0.54–0.71; n = 16 631; follicle size ≥ 16 mm) per oocyte. Based on per mature oocyte or two‐pronuclei zygote, follicle size showed little predictive capacity for embryological parameters. Conclusions Follicle size could predict oocyte developmental competence with corresponding optimal thresholds identified. However, the benefits for embryological fate may plateau at follicle sizes ≥ 15–16 mm once the oocytes achieve maturation or fertilisation.