Frontomaxillary facial angle at 11 + 0 to 13 + 6 weeks: effect of plane of acquisition.
OBJECTIVE
To determine the range of positions of the fetal head in which a three-dimensional (3D) volume is acquired for subsequent successful assessment of the frontomaxillary facial (FMF) angle.


METHODS
We obtained 3D volumes of the fetal head at 11 + 0 to 13 + 6 weeks. The volumes were acquired with the head in different positions and reconstructed to obtain a mid-sagittal section and demonstrate the maxilla, palate and frontal bone, which constitute the landmarks for the assessment of the FMF angle.


RESULTS
In the reconstructed mid-sagittal sections, it was possible to demonstrate the landmarks that define the FMF angle in most of the cases when the 3D volume acquisition plane was: (a) mid-sagittal, with the angle between the face of the transducer and the direction of the fetal nose being about 0-99 degrees, 150-199 degrees and 330-359 degrees; (b) transverse at the level of the biparietal diameter when the angle between the transducer and the midline echo of the brain was 0-29 degrees; and (c) oblique around the crown-rump axis when the angle from the mid-sagittal plane was 0-49 degrees. However, the measurement of the FMF angle was artificially increased when in the mid-sagittal plane the angle was 40-99 degrees and 150-199 degrees.


CONCLUSIONS
Successful assessment of the FMF angle by 3D ultrasound is dependent on the plane and angle of the volume acquisition.
Plasencia
W
W
Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, London, UK.
Dagklis
T
T
Pachoumi
C
C
Kolitsi
E
E
Nicolaides
K H
KH
D004314:Down Syndrome / Q000000981:diagnostic imaging* / Q000196:embryology; D005260:Female; D005624:Frontal Bone / Q000000981:diagnostic imaging* / Q000196:embryology; D005865:Gestational Age; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008437:Maxilla / Q000000981:diagnostic imaging* / Q000196:embryology; D011247:Pregnancy; D011446:Prospective Studies; D015203:Reproducibility of Results; D016216:Ultrasonography, Prenatal / Q000379:methods*