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| Cell-free DNA screening | First trimester screening | Second trimester serum screening | CVS and Amniocentesis | |
|---|---|---|---|---|
| When | 9-10 weeks until term | 10-14 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% | 2.5-5% | 5% | <1% |
| Other conditions included and detection rates | T18 98%
T13 99% Variable/optional inclusion: Sex chromosome aneuploidy, Trisomy 22 and 16, Microdeletion/duplication conditions - uncertain | 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 | CVS/amniocentesis or consider repeat cfDNA | 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 #226 Screening for Fetal Chromosome Abnormalities. 2020.
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.
Rose NC, Barrie ES, Malinowski J, Jenkins GP, McClain MR, LaGrave D, Leung ML; ACMG Professional Practice and Guidelines Committee. Systematic evidence-based review: The application of noninvasive prenatal screening using cell-free DNA in general-risk pregnancies. Genet Med. 2022 May 10:S1098-3600(22)00714-6.
SMFM, Consult Series #36: Prenatal aneuploidy screening using cell-free DNA. Am J Obstet Gynecol, 2015; 212(6): 711-6.
Updated October 2022