prenatal testing (test 3)

NT scan

scan at 11-13 weeks

quad screen

scan at 15-18 weeks

triple screen

test at 9-13 weeks

AFP hCG Estriol Inhibin-A

what does the quad screen test?

AFP hCG Estriol

what does the triple screen test?

Triple screen

• Also Known as Triple Test, Multiple Marker Screening and AFP Plus • Tests three specific substances: AFP, hCG, and Estriol • Abnormal results doesn't diagnosis genetic defect, only points to increase risk

Sequential screening

• Assessment given after triple screen and NT scan, typically during first trimester. • If the result indicates increased risk of having a chromosomal abnormality, diagnostic testing like CVS is suggested. • If results indicates low risk, patient offered quad screen in second trimester and the risk assessment adjusted that incorporating results from both first and second trimesters.

Quad screen

• Essentially the same as the triple screen except pregnancies at risk for Down Syndrome have higher Inhibin-A levels. • Lower false positive rate than triple screen

Cordocentesis

• Fetal blood aspirated from umbilical cord • Fast chromosomal results • Helpful with confirmation of amniocentesis results or anomaly found later in gestation

Amniocentesis

• Indication-AMA, abnormal AFP levels, hx of previous chromosomal abnormalities • Timing between 14-20 weeks • Later in gestation to determine fetal lung maturity (lecithin/sphingomyelin ratio) • US used as guide

Cell Free Fetal DNA after 10 weeks

• MaterniT21™ PLUS, Harmony ™, Panorama™, Verifi ™ • Measures amount of free fetal DNA in maternal serum

CVS chorionic villus sampling

• Sample obtained of trophoblastic tissue • Done between 9-12 weeks • Provides earlier diagnosis • Decisions about pregnancy can be made in first trimester

AFP

• Serum protein produced by fetal liver, excreted into amniotic fluid • Amniotic fluid obstruction causes protein to accumulate • AFAFP or MSAFP • Decreased MSAFP with trisomies • Increase has multiple causes, page 1195

Integrated screening

• Uses results first-trimester triple screen, the NT measurement, and the second-trimester quadruple screen. • Gives single assessment of risk after all of these screening tests are completed. • 90 to 96 percent of Down syndrome cases.