Assessment of the fetal nasal bone at 11-14 weeks of gestation by three-dimensional ultrasound

Abstract

Objective: To evaluate the benefit of three-dimensional (3D) ultrasound in the examination of the fetal nasal bone at 11-14 weeks of gestation. Method: We examined the fetal nasal bone in 120 stored volumes acquired transabdominally with a 3D scanner from singleton pregnancies at 11-14 weeks of gestation. The volume acquisition had been performed following conventional ultrasound examination that had demonstrated presence of the fetal nasal bone. The volumes were obtained with two-dimensional (2D) start images in transverse, coronal mid-sagittal, parasagittal and oblique longitudinal sections of the fetal head. Results: In the transverse and coronal sections, a satisfactory image demonstrating presence of the nasal bone was achieved in only three and one, respectively, of the 20 volumes that we obtained. In mid-sagittal sections, the nasal bone was always visible when the angle was within a range of 30-60°, without the need for sectional image analysis. None of the images with an angle > 60° or < 30° was satisfactory. In the parasagittal sections with the fetal profile at 45°, a good-quality image of the nasal bone was possible in all cases that were examined, irrespective of the distance from the mid-sagittal plane. In the oblique longitudinal sections with the fetal profile at 45°, there were 10 volumes where the 2D start section was at 0-25° from the midline and in all these cases the nasal bone was successfully visualized. In contrast, only 5/20 cases where the 2D start section was at 25-90° from the midline provided a satisfactory image demonstrating the nasal bone. In 5/10 volumes obtained with the fetus facing downwards the nasal bone was visible in both the 2D and 3D images. Conclusion: In a 3D volume the extent to which the nasal bone can be demonstrated to be present in a given reconstructed section is entirely dependent on obtaining a good initial 2D view. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.