Are the first trimester volumetric measurements with two dimensional ultrasonography satisfactory?

Abstract

Objectives: Aim was to examine volumetric measurement of first trimester structures with two-dimensional ultrasonography (2D US) and evaluate necessity of three-dimensional (3D) volume measurements instead of 2D during first trimester. Methods: Using 2D transvaginal ultrasound imaging, the crown rump length (CRL), yolk sac (YS) and gestational sac (GS) diameters were recorded in 176 women with gestational age <11 weeks. Volume measurements were done by using a simplified formula for the volume of a prolate ellipsoid: V = 0.523 × length × height × width. Results: The mean CRL value was 19.6 ± 8.8 mm. The mean YS, GS and embrionic volume (EV) varied from 0.02–0.13, 5.5–37.72, 0.024–3.31 cm3 between 6+6 and 10+6 weeks, respectively. There was moderate positive correlation between EV versus GS volume and YS volume versus EV.Conclusions: 2D US still can provide adequate information in volumetric examination of regular shaped objects. But 3D US is useful in volumetric measurements of irregular shaped structures and for screening of fetal abnormalities.