Fig. 1

Measurements of different facial profile markers. A, frontomaxillary facial angle (FMF, 12^+ 5 weeks); B, maxilla-nasion-mandible angle (MNM, 12^+ 5 weeks); C, facial maxillary angle (FMA, 12^+ 5 weeks); D, inferior facial angle (IFA, 12^+ 5 weeks); E, frontal space distance (FSD, 13^+ 5 weeks); F, profile line distance (PL distance, 12^+ 5 weeks); G, palatine maxillary diameter (PMD, 12^+ 5 weeks); H, maxillary gap (MG, 12^+ 5 weeks). A, FMF angle: the angle between the extension line along the superior edge of the palate and the tangent line of the frontal bone on the mid-sagittal plane with the front end of the palate as the apex [14]. B, MNM angle: the angle between the maxilla–nasion line and the mandible–nasion line. The nasion was defined as the most anterior point at the intersection of the frontal and nasal bone [15]. C, FMA: the angle between the line overlying the maxilla and the line across the mentum tip and upper lip [16]. D, IFA: the angle between the line orthogonal to the vertical part of the forehead at the level of the synostosis of the nasal bones and a second line joining the tip of the mentum to the anterior point of the more protruding lip [17]. E, FSD: the maximum perpendicular distance from the mandibulo-maxillary line (MML) to the most prominent part of the fetal forehead. The MML was an extended line intersecting the most anterior portions of the mandible and the maxilla [18]. F, PL distance: the maximum perpendicular distance from the facial profile line (FPL) to the outer border of the forehead. The FPL was the line passing through the middle point of the anterior border of the mandible and the nasion [19]. G, PMD: the shortest hyperechoic distance from the ossified posterior palatine process to the anterior ossified part of the maxilla [20]. H, MG: if present, the size of the gap was measured [21]