|Indications for use of US|
US is used in early pregnancy to confirm the presence of an embryo. In mid pregnancy, a "screening" ultrasound is performed to evaluate for fetal anomalies. The brain, heart, stomach bubble, kidneys, bladder, umbilical cord and other structures are carefully evaluated to determine if they are morphologically normal.
The image on the right shows the fetal head in the axial plan. The outer skull is not yet ossified, which is why we are able to US "through" it. The stars depict the right and left cerebellar hemispheres. The line demarcates the foramen magnum. The + symbols are located on the thalamus. Identifying these normal structures and confirming their normal size helps to exclude major congenital anomalies.