Biparietal diameter (BPD) is measured from ourter cortex of the near parietal bone to the innter cortex of the far parietal bone on a symmetric image at the level of the thalami. Cerebellar hemispheres should not be seen in this plane. The biparietal plane is near-parallel to the ultrasound beam.
Head circumference (HC) is measured in this case by an elliptical tool on the same imaging plane.
Abdominal circumference (AC) is measured at the level of liver, preferentially at the confluence of the right and left portal vein and with stomach on view from outer margin of skin.
Femur length (FL) measurement should be obtained with the femur perpendicular or near perpendicular to the ultrasound beam. Only diaphysis is measured.