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

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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.