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Table 1-7

Summary of Parental Genetic Screening Testsa

TestComponentsTesting Time FrameCommentsDetection Rate for Trisomy 21
First trimester screen

  • Maternal age

  • Maternal serum:

    • hCG

    • PAPP-A

  • Fetal ultrasound:

    • Nuchal translucency

    • ±Nasal bone

10-13 6/7 wkProvides risk for trisomy 21 and 13/18; improved detection when fetal nasal bone is assessed82%-87%95% (including nasal bone assessment)
Quad screenMaternal serum:

  • hCG

  • MSAFP

  • uE3

  • DIA

15-22 6/7 wkProvides risk for trisomy 21, 18, and open NTDs81%
Combined screening (integrated)

  • Fetal nuchal translucency

  • Maternal serum:

    • PAPP-A

    • hCG

    • MSAFP

    • uE3

    • DIA

First and second trimester (as noted above)Detection rate for trisomy 21 equivalent to first trimester screen when nasal bone is included94%-96%
Combined screening (sequential)Patient given results of first trimester screen and then decide whether to undergo invasive testing (if positive) or quad screen (if negative).First and second trimester (as noted above)Allows patients to decide the extent of testing they wish to pursue95%
MSAFPMSAFPSecond trimesterProvides risk for open NTDsNA
Cell-free fetal DNA analysisMaternal blood draw with analysis of fetal DNA10 wk and laterOnly recommended for patients at higher risk of aneuploidy>98%

Abbreviations: β-hCG, β-human chorionic gonadotropin; DIA, dimeric inhibin A; MSAFP, maternal serum α-fetoprotein; NTDs, neural tube defects; PAPP-A, pregnancy-associated plasma protein-A; uE3, unconjugated estriol.


aData from American College of Obstetricians and Gynecologists Committee on Practice Bulletins—Obstetrics, Committee on Genetics, Society for Maternal-Fetal Medicine. ACOG Practice Bulletin No. 163: screening for fetal aneuploidy. Obstet Gynecol. 2016;127:e123-e137.