Many sonographically identified markers, associated with chromosomal disorders including amongst others, short femur, short humerus, increased nuchal fold thicken­ing, pyelectasis, echogenic bowel, echogenic cardiac foci, and choroids plexus cysts, have been described. In the first trimester of pregnancy, a common feature of many chro­mosomal defects is the increased nuchal translucency (NT) thickness, but in later stages of pregnancy each chromo­somal defect has its own syndromal pattern of abnormali­ties. Over the last 15 years, several studies have shown that genetic sonography may detect 70-80% of the fetuses with Down’s syndrome (DS), as well as a significant pro­portion of fetuses with other chromosomal abnormalities, and by evaluating the presence or absence of multiple aneuploidy markers. Genetic sonography has been pro­posed as a way of adjusting the risk for DS, and therefore, the need for amniocentesis, in high-risk for aneuploidy pregnant women.

Key words: Chromosomal abnormalities; Genetic sonogram; Prenatal diagnosis; Chromosomal markers; Down’s syndrome (DS); Trisomy 21; Aneuploidy.