<prompt> MSAFP levels should generally be done at what gestational age?9 weeks11 weeks15 weeks20 weeks  <response>: Ans. C. 15 weeks. Ref. Textbook of Obstetrics D.C. Dutta 7th Ed pg. 106; 493MSAFP: AFP is a oncofetal Molecular wt 70,000. it is produced by yolk sac and fetal liver. Highest level in fetal serum and amniotic fluid is reached around 13 weeks and thereafter it decreases. Maternal serum levels peak around 32 weeks of gastation. MSAFP level is elevated in:- Wrong gestational age- Open neural tube defects- Multiple pregnancy- Rh iso- IUD- Anterior abdominal wall defects- Renal anomalies Low levels are found in:- Trisomies Downs syndromeGTD Test is done between 15-20 weeks. Triple test is also performed at 15-18 weeks. In Downs levels of MSAFP and UE3 tend to be low and while that of hCG high. MSAFP value of 2.5 multiples of medians is taken as cut-off point. Elevated MSAFP detects 85 of all neural tube defects.Prenatal diagnostic tests. MSAFPMSAFP, hCG, UE3 Triple testBeta-hCG PAPP-A NTSoft tissue marker Nuchal translucency1.Time weeks14-2014-1811-1411-142.ObservationMSAFP yMSAFP ss, hCG y, UE3 sshCG y,PAPP-A ssNT 3 mm3.Anomaly to detectOpen NTDDowns syndromeDowns syndromeDowns syndrome, Turners syndrome and others4.CommentCut off level of 2.5 MOM can detect 90 of anencephaly, 80 open spina bifida.A cut off value of 1 in 200, is screen positive.A cut off value 1 in 300 is screen positive.Detection of Downs syndrome is high 92, when NT and NB are combined.5.Detection rate657385-8970-806.False positive rate3-5555-6 