Prenatal aneuploidy testing comparison table


Select prenatal screening and diagnostic testing options for Trisomy 21 and other fetal aneuploidies


  Cell-free DNA screening First trimester screening Second trimester serum screening CVS and Amniocentesis
When 9-10 weeks and over 11-14 weeks 15-22 weeks CVS: 10-13 weeks
Amniocentesis: 15-16 weeks and over
How performed Maternal blood Maternal blood + ultrasound Maternal blood Invasive procedure
Risks None None None Risks of miscarriage
CVS 1/455
Amniocentesis 1/900
T21 detection rate >99% 85% 81% >99%
T21 False-positive rate <1% 5% 5% <1%
Other conditions included and detection rates T18 97%
T13 92%
Variable/optional inclusion:
Sex chromosome aneuploidy – 91%
Microdeletion/duplication conditions - uncertain
T18 84%
T13 84%
T18 80%
ONTD 90%
All aneuploidies >99%
OFD (Amniocentesis) >95%
Other genetic conditions if indicated – depends on condition
Unreportable/no call rate <1%-5% <1% <1% 1-3%
Results follow-up
Normal Screen for OFD in 2nd trimester Screen for OFD in 2nd trimester None Screen for OFD in 2nd trimester if CVS performed
Abnormal CVS/US/Amniocentesis CVS/US/Amniocentesis CVS/US/Amniocentesis None
Unreportable/no-call Repeat or CVS/amniocentesis Redraw Redraw Repeat or cfDNA

CVS=Chorionic villus sampling; OFD=Open fetal defect; T13=Trisomy 13; T18=Trisomy 18; T21=Trisomy 21; US = Ultrasound


ACOG and SMFM, Practice bulletin #162: Prenatal diagnostic testing for genetic disorders. 2016.

ACOG and SMFM, Practice bulletin #163: Screening for fetal aneuploidy. 2016.  

Driscoll, D.A., Second trimester maternal serum screening for fetal open neural tube defects and aneuploidy. Genet Med, 2004; 6(6): 540-1. 

Fairbrother, G., et al., Prenatal screening for fetal aneuploidies with cell-free DNA in the general pregnancy population: a cost-effectiveness analysis. J Matern Fetal Neonatal Med, 2016; 29(7): 1160-4. 

SMFM, Consult Series #36: Prenatal aneuploidy screening using cell-free DNA. Am J Obstet Gynecol, 2015; 212(6): 711-6. 

Wilson, K.L., et al., NSGC practice guideline: prenatal screening and diagnostic testing options for chromosome aneuploidy. J Genet Couns, 2013; 22(1): 4-15.

Updated May 2019