The relationship between oocyte maturation and follicle size: A comparative analysis of 2D and 3D ultrasound

To compare the ability of three-dimensional (3D) and conventional two-dimensional (2D) ultrasound to predict oocyte maturity during in vitro fertilization cycles, and to evaluate their contribution to trigger timing and to the determination of optimal cut-off values for maximizing metaphase II (MII) oocyte yield using automated volume-calculation software.

Forty-three infertile women who had ≤5 follicles, were younger than 40 years, had a body mass index <30, and had no previous oocyte maturation problems were included in this retrospective study. Follicle diameter was measured using 2D ultrasound, while follicle volume was measured using 3D ultrasound with SonoAVC software. The obtained values were compared with those from MII oocytes, and receiver operating characteristic (ROC) analysis and logistic regression were performed.

A total of 203 oocytes were analyzed; 70% of them were in the MII stage. In the ROC analysis, the optimal cut-off for 2D measurement was determined to be 17.05 mm [area under curve (AUC)=0.737], and for 3D measurement, it was 1.83 cm³ (AUC=0.709). 2D measurements showed specificity, while 3D measurements showed sensitivity. In logistic regression analysis, both 2D diameter and 3D volume were found to be independent predictors of MII oocyte development.

Our findings suggest that 3D ultrasound measurements may provide greater sensitivity for predicting oocyte maturity. However, falsepositive results may occur in the presence of multiple or nested follicles, and observer dependence cannot be completely eliminated. Therefore, optimization and large-scale validation studies are needed to improve the accuracy of the method.