**1.1. Sagittal planes**

In order to assess the normality of the fetus profile, sagittal planes of the face are used (**Figure 1**).

One of the US parameters used to obtain an exact measurement of the position of the anterior end of the maxilla to the forehead is the angle between the surface of the palate and the frontal bone examined in a mid-sagittal view of the fetal face, called the frontomaxillary facial angle [2]. This angle is increased in fetuses with trisomy 21, and it is believed that the reason for this is the hypoplasia or posterior displacement of the palate [2, 3].

**Figure 2.** Axial scan passing through the orbits of a normal second trimester fetus.

inside the orbit.

**Figure 3.** The interocular distance (IOD) and binocular distance (BOD) are demonstrated in this scan. The lens is visible

Congenital Abnormalities of the Fetal Face http://dx.doi.org/10.5772/intechopen.73072 93

Ears are well visualized in parasagittal scans tangential to the calvarium. In late gestation, significant details of the anatomy of the external ear can be seen.
