First‐trimester screening for trisomy 21 by free beta‐human chorionic gonadotropin and pregnancy‐associated plasma protein‐A: impact of maternal and pregnancy characteristics

Abstract Objectives To use multiple regression analysis to define the contribution of maternal variables that influence the measured concentration of free beta‐human chorionic gonadotropin (β‐hCG) and pregnancy‐associated plasma protein‐A (PAPP‐A), and the interaction between these covariates, in fi... View More