A combination of maternal age and history, fetal nuchal translucency thickness, and levels of maternal serum pregnancy-associated plasma protein A (PAPP-A) and free beta-human chorionic gonadotropin (β-hCG) in the first trimester has been shown to be able to detect about 90% of cases of trisomy 21 (5). This evidence concerns the gene PAPPA and trisomy 21.