Current methods of non-invasive prenatal screening of trisomy 18 increase the detection rate by integration of nuchal translucency measurement and pregnancy-associated plasma protein-A in the first trimester and various maternal serum biochemical markers, including alpha fetoprotein, unconjugated estriol, human chorionic gonadotrophin and inhibin-A in the second trimester [2]. The gene discussed is AFP; the disease is trisomy 18.