RESUMEN
Ultrasound has become an integral component of obstetric care, with the vast majority of patients having at least one ultrasound examination during pregnancy. Recent advances in obstetric ultrasonography (USG) have increased its importance in managing pregnancies at risk for aneuploidy and structural abnormality. Antenatal screening of aneuploidy, particularly Down syndrome includes biochemical markers, USG and invasive tests like chorionic villus sampling (CVS) and amniocentesis. In this article, we review and compare these screening modalities with emphasis on USG. In light of current literature, we will discuss first trimester sonographic markers associated with aneuploidy viz. nuchal translucency (NT), fetal nasal bone and ductus venosus flow and their statistical as well as clinical significance in the detection of aneuploidy. We will review the current data and status of first trimester screening for aneuploidy.