A Novel Technique for the Semi-Automated Measurement of Embryo Volume: An Intraobserver Reliability Study

The aim was to assess intraobserver reliability of a new semi-automated technique of embryo volumetry. Power calculations suggested 46 subjects with viable, singleton pregnancies were required for reliability analysis. Crown rump length (CRL) of each embryo was analyzed using 2-D and a 3-D dataset acquired using transvaginal ultrasound. Virtual organ computer-aided analysis (VOCAL) was used to calculate volume of gestation sac (GSV) and yolk sac (YSV) and SonoAVC (sonography-based automated volume count) was used to quantify fluid volume (FV). Embryo volume was calculated by subtracting FV and YSV from GSV. Each dataset was measured twice. Reliability was assessed using Bland-Altman plots and intraclass correlation coefficients (ICCs). Fifty-two datasets were analyzed. Median embryo volume was 1.8cm3 (0.1 to 8.1 cm3); median gestational age 7 + 4 weeks; median CRL 13 mm (2 to 29 mm). Mean difference of embryo volume measurements was 0.1cm3 (limits of agreement [LOA] -0.3 to 0.4 cm3); multiples of mean (MoM) 0.38; mean difference of CRL measurements 0.3 mm (LOA -1.4 to 2.0 mm), MoM = 0.26. ICC for embryo volume was 0.999 (95%CI 0.998 to 0.999), confirming excellent intraobserver agreement. ICC for CRL was 0.996 (95%CI 0.991 to 0.998). Regression analysis showed good correlation between embryo volume and CRL (R2 = 0.60). The new semi-automated 3-D technique provides reliable measures of embryo volume. Further work is required to assess the validity of this technique. (E-mail: shyamaly@doctors.org.uk)