Reliable individual risk calculation for trisomy (T) 13, 18, and 21 in first-trimester screening depends on good estimates of the medians for fetal nuchal translucency thickness (NT), free ß-subunit of human chorionic gonadotropin (hCGß), and pregnancy-associated plasma protein-A (PAPP-A) in maternal plasma from unaffected pregnancies. Means and SDs of these parameters in unaffected and affected pregnancies are used in the risk calculation program. Unfortunately, our commercial program for risk calculation (Astraia) did not allow use of local medians. We developed 2 alternative risk calculation programs to assess whether the screening efficacies for T13, T18, and T21 could be improved by using our locally estimated medians.