These voluntary screening tests which are used to evaluate the risk of DS consist of measuring combinations of biomarkers in maternal serum, including alpha fetoprotein (AFP), total human chorionic gonadotropin (hCG), free beta subunit of hCG (β-hCG), unconjugated estriol (uE3), pregnancy-associated plasma protein A (PAPP-A), proform of eosinophil major basic protein (ProMBP), inhibin-A, and placental growth factor (PGF). Here, PGF is linked to Dravet syndrome.