First-trimester crown-rump length and embryonic volume of aneuploid fetuses measured in virtual reality.

OBJECTIVES

To examine whether embryonic volume (EV), as measured using three-dimensional (3D) ultrasound and a virtual reality approach, is a better measure of growth restriction than is crown-rump length (CRL) in aneuploid fetuses.

METHODS

We retrospectively measured CRL and EV in prospectively collected 3D ultrasound volumes of 55 aneuploid fetuses using the Barco I-Space VR system. The gestational age ranged from 11 + 2 to 14 + 4 weeks. We compared our measured data with previously published reference curves for euploid fetuses. Delta-values were calculated by subtracting the expected mean for euploid fetuses of the same gestational age from observed values. The one-sample t-test was used to test the significance of differences observed.

RESULTS

The CRL measurements of fetuses with trisomy 21 (n = 26), trisomy 13 (n = 5) and monosomy X (n = 5) were comparable with those of euploid fetuses, but in fetuses with trisomy 18 (n = 19) the CRL was 14.5% smaller (P < 0.001). The EV in fetuses with trisomies 21, 18 and 13 and monosomy X was smaller than in euploid fetuses (-27.8%, P < 0.001; -39.4%, P < 0.001; -40.9%, P = 0.004; and -27.3%, P = 0.055, respectively).

CONCLUSIONS

When relying on CRL measurements alone, first-trimester growth restriction is especially manifest in trisomy 18. Using EV, growth restriction is also evident in trisomies 21 and 13 and monosomy X. EV seems to be a more effective measurement for the assessment of first-trimester growth restriction in aneuploid fetuses.