ABSTRACT
During pregnancy several congenital anomalies may occur and these result in structural, behaviour, functional, metabolic and neuromuscular defects (Sadler 2010, Lewis 2007, Ferraris & Muñoz 2007).
In the second trimester, ultrasound screening of aneuploidies and fetal malformations is done primarily with fetal morphological study, complemented by biochemical screening (Regateiro 2003, Geipel et al. 2010, Kagun et al. 2009, Benoit & Chaoui 2005). On the ultrasonographic evaluation, the presence or absence of nasal bone and nuchal fold thickness is considered to be an important marker (Geipel et al. 2010, Persico et al. 2008). The presence of hypoplasia of nasal bone happens in 0.4 to 6% of euploid fetuses. However, this is a characteristic often expressed on trisomies 13, 18, and 21 and on Apert, Cri-du-Chat and Lange syndromes. It is also detected in mesomelic dysplasia (Kagun et al. 2009, Benoit & Chaoui 2005, Chung et al. 2010, Persico et al. 2010, Guis et al. 1995, Teoh et al. 2009, Tuxer et al. 2003).
