Fig. 1From: Reference ranges for foetal nasal bone length, prenasal thickness, and interocular distance at 18 to 24 weeks’ gestation in low-risk pregnancies a Ultrasound image of a foetus showing the exact mid-sagittal plane of the face with its sonographic landmarks and measurement of nasal bone length and prenasal thickness. b The measurement of interocular distance in the axial plane. IOD: interocular distanceBack to article page