Inter- and intra-observer variation of fetal volume measurements with three-dimensional ultrasound in the first trimester of pregnancy

Objectives: To determine the inter- and intra-observer variation of volume calculations of human fetuses at a gestational age of 11 ⁺⁰-13 ⁺⁶ weeks by three-dimensional ultrasound (3DUS). Methods: 3DUS datasets were acquired during nuchal translucency measurements. The fetal volume (FV) was measured in 65 cases by two independent investigators. The Virtual Organ Computer aided AnaLysis (VOCAL™) imaging software was used to manually calculate the FV (rotational angle 9°). Inter- and intra-observer variation were assessed by Bland-Altman plots and intraclass correlation coefficients (ICC). Results: Both inter- and intraobserver reproducibility were highly reliable as shown by the Bland-Altman plots and an ICC of respectively 0.934 and 0.994. Conclusion: FV calculation by 3DUS with VOCAL and a rotational angle of 9° is feasible and has a high inter- and intraobserver reliability in the first trimester of pregnancy.