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.

Method: 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.