<prompt> Screening test used in first trimester for aneuploidy -PAPP-A estradiolPAPP-A AFPPAPP-A beta HCGBeta HCG inhibin  <response>: Ans. isci.e., PAPP-A beta HCG1st trimester aneuploidy screening:Human chorionic gonadotropin either intact or free b-hCG.Pregnancy-associated plasma protein A PAPP-A.Fetal Down syndrome in 1st trimester:Higher serum free beta-hCG level.Lower PAPP-A levels.Trisomy 18 13:Lowered levels of both HCG PAPPP-A.2nd trimester analytes:Serum integrated screening.Accuracy of aneuploidy detection:Greater on combination with,Sonographic NT measurement. 