Prenatal diagnosis of fetal chromosomal abnormalities is the most common indication for invasive prenatal testing. The prevalence of chromosomal abnormalities in clinically recognized early pregnancy loss is greater than 50%(1). Fetuses with aneuploidy account for 6-11% of all still births and neonatal deaths(2). Chromosomal abnormalities that are compatible with life but cause considerable morbidity occur in 0.65% of newborns, and structural chromosomal rearrangements that will eventually affect reproduction occur in 0.2% of newborns(3). Consequently, screening and diagnostic programs to detect the most common autosomal trisomies in liveborn infants, including Down syndrome, are well established. The purpose of this document is to provide clinical management guidelines for the prenatal diagnosis of these aneuploidies.