P-702 Prediction of oocyte maturity via automated volumetric follicle measurements on the day of triggering final oocyte maturation. An observational cohort study
Authors: Makris A , Lainas G , Lainas T , Xenariou M , Petsas G , Zorzovilis I , Kolibianakis E 
Published: June 2022

Abstract

Study question
Can automated measurements of follicular volume by three-dimensional (3D) ultrasound predict the number of mature oocytes retrieved better than two-dimensional (2D) measurements of follicles?

Summary answer
Automated measurements of follicular volume by 3D ultrasound have similar predictive ability of the number of mature oocytes retrieved as manual 2D measurements of follicles.

What is known already
Accurate assessment of the size and number of follicles during ovarian stimulation is important to determine the day of triggering final oocyte maturation and subsequent oocyte retrieval, in order to achieve the optimal number of mature oocytes. Follicles with a diameter ≥11mm on the day of triggering are often considered to contribute the most towards the final number of mature oocytes. It has also been shown that 3D follicle volumes offer a more physiological measurement and may be a more objective than 2D follicle diameters. However, to date, the correlation between diameters and volumes has not been properly evaluated.

Study design, size, duration
Prospective observational cohort study of 75 women undergoing ICSI between 01/2021 and 09/2021 in a private ART centre. In each patient, two dimensional-2D and three dimensional-3D transvaginal ultrasound (SonoAVC; GE Medical Systems), was used to assess differences in the number and size of follicles on the day of triggering final oocyte maturation. SonoAVC automatically calculates the volume of the follicle while manual-2D value is calculated as the mean of the maximal follicular dimensions x-y.

Participants/materials, setting, methods
Patients underwent ovarian stimulation with recombinant-FSH and GnRH antagonists. Statistical analysis involved robust linear regression with dependent variable the number MIIs retrieved and independent variables the number of follicles ≥11mm (via 2D) and the number of follicles with volume ≥0.7ml (via SonoAVC). 0.7ml was used as it is a close approximation to the volume of a sphere with diameter 11mm. This was confirmed by identifying the actual volume of aspirated follicles 11mm (unpublished data).

Main results and the role of chance
A high correlation of R = 0.922 was observed between manual-2D and automated-3D assessment in the number of follicles with volume ≥0.7ml and those with mean diameter ≥11mm. In addition, no differences were found in the number of follicles with volume ≥0.7ml vs the number of follicles with diameter of ≥ 11mm (median 9.0, IQR: 5.0 – 14.5 vs. median 10.0, IQR: 6.75 – 18, respectively) on the day of triggering final oocyte maturation. The median number of MIIs collected was 9.0 (IQR: 5.0 – 13.25).
The predictive capability of follicles with volume ≥0.7ml in regards to the number of MII collected was found to be R2=0.736, which is higher than the predictive capability of follicles ≥11mm (R2=0.629). These findings suggest that the number of follicles with a volume ≥0.7ml offers at least a similar predictive capability as the traditionally used number of follicles ≥11mm.

Limitations, reasons for caution
While the volume of 0.7ml was found to be closely correlated with the size of 11mm, the predictive capability of other follicular volumes needs to also be compared, since follicles are rarely spheres, especially in hyperstimulated ovaries and therefore even better prediction of oocyte maturation may arise from another volume.

Wider implications of the findings
Manual-2D ultrasound and automated-3D volumetric assessment of follicles provide similar predictive value of the number of mature oocytes retrieved. Therefore volumetric measurements can possibly be used during assessment of ovarian stimulation, instead of mean diameter. However, their clinical effectiveness needs to be tested in a robust clinical trial.

Trial registration number
N/A