Nuchal translucency

The magnification of the image should be such that the fetal head and upper thorax occupy the whole screen.

• A mid sagittal section of the fetus must be obtained. In this section the echogenic nasal bone and rectangular palate are seen separately. Rotation of the head away from the midline results in non-visibility of the tip of the nose and the appearance of the maxillary bone as an echogenic structure between the nasal bone above and the anterior part of the palate below. With further rotation from the midline the nasal bone disappears and there is enlargement of the maxillary bone and coalescence with the palate.
• The fetus should be in a neutral position, with the head in line with the spine. When the fetal neck is hyperextended the measurement can be falsely increased and when the neck is flexed, the measurement can be falsely decreased.
• Care must be taken to distinguish between fetal skin and amnion.