Screening for trisomy at 11-13 weeks' gestation: use of pregnancy-associated plasma protein-A, placental growth factor or both.

In first-trimester screening for trisomy, the preferred biochemical marker is PAPP-A rather than PlGF, especially when biochemical testing is carried out during the 11th week of gestation or earlier. However, if PlGF was to be used rather than PAPP-A, the same detection rate can be achieved but at a higher FPR. This may be an acceptable compromise to minimize cost and achieve effective screening for both trisomy and PE. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.