Start with a "BPD view", and observe the general shape of the head. This transverse view of a fetal head shows the appropriate oval shape. A head that is too elongated is "dolichocephalic", a finding that is often associated with anhydramnios or breech presentation. A round head- termed "brachycephalic"- suggests the presence of a genetic abnormality. A lemon shaped head is usually a sign of spina bifida, as shown in this 16 week fetus.
Also visible in the "BPD view" are the thalamus and the cavum septum pellucidum. In a slightly higher view the anterior horns of the lateral ventricles are seen, as is the midline falx cerebri
When the transducer is rotated slightly, bringing into view structures that are lower in the brain posteriorly, the atria and posterior horns of the lateral ventricles are seen. The choroid plexus should fill the ventricle from side to side. The choroid plexus appears quite large in the early second trimester compared to its appearance at term.
By rotating the transducer slightly further in a posterior direction the cerebellar hemispheres and cysterna magna are seen.
Rotating the transducer the other direction from the "BPD view", the orbits are visualized. Continuing the rotation in the same direction, a coronal view of the fetal face in obtained, and the nose, chin and both lips can be seen.
