Second trimester Down syndrome markers in affected and unaffected pregnancies
Second trimester Down syndrome markers in affected and unaffected pregnancies
The quadruple test for Down syndrome screening is performed in the early second trimester (optimally at 15 to 18 weeks of gestation) and consists of AFP, uE3, total/intact hCG or free beta hCG, and inhibin A measurements. Graphs show the overlapping distributions between affected and unaffected pregnancies.
AFP: alpha-fetoprotein; uE3: unconjugated estriol; hCG: human chorionic gonadotropin.