First-Trimester Crown-Rump Length and Embryonic Volume of Fetuses with Structural Congenital Abnormalities Measured in Virtual Reality: An Observational Study

markdownabstractBackground With the introduction of three-dimensional (3D) ultrasound it has become possible to measure volumes. The relative increase in embryonic volume (EV) is much larger than that of the crown-rump length (CRL) over the same time period. We examined whether EV is a better parameter to determine growth restriction in fetuses with structural congenital abnormalities. Study Design, Subjects, and Outcome Measures CRL and EV were measured using a Virtual Reality (VR) system in prospectively collected 3D ultrasound volumes of 56 fetuses diagnosed with structural congenital abnormalities in the first trimester of pregnancy (gestational age 7+5 to 14+5 weeks). Measured CRL and EV were converted to z-scores and to percentages of the expected mean using previously published reference curves of euploid fetuses. The one-sample t-test was performed to test significance. Results The EV was smaller than expected for GA in fetuses with structural congenital abnormalities (-35% p<0.001, z-score -1.44 p