Several maternal serum biomarkers used in routine fetal Down syndrome screening, such as free beta-human chorionic gonadotropin (β-hCG), inhibin-A, pregnancy-associated plasma protein-A (PAPP-A), alpha-fetoprotein (MAFP), and unconjugated estriol (uE3), are probably useful in predicting fetal Hb Bart’s disease. The gene discussed is AFP; the disease is Down syndrome.