Cell-free DNA screening
for trisomy 13, 18 and 21

Healthcare Professional Space

The Cell‐free DNA screening for trisomy 13,18 and 21may be proposed to every woman in the following situations:

1. Primary detection (serum markers not performed)

2. After maternal serum screening:

Screening strategy:

  • 1st trimester maternal combined screening
  • 2nd trimester maternal integrated screening
  • 2nd trimester (serum markers only)

Risk:

  • High (>1/250)
  • Intermediary (1/250-1/1000)
  • Weak (< 1/1000)
  • Serum markers out of range (MoM PAPP-A <0,25 or >2,5 and/or MoM hCG <0,25 or >5)

3. Patient with prior medical history of fetal aneuploidy

4. Parental robertsonian translocation involving a chromosome 13 or 21

5. Maternal age 35 years or older (or according to local recommendations)

6. Twin pregnancy, without increased nuchal translucency or other abnormalities at ultrasound scan

However, this test must not be proposed to date.

  •  This test should not be proposed in case of signs at ultrasound scan (including nuchal translucency equal or above 95th percentile) due to a risk around 2,5 % of unbalanced abnormalities other than the ones detected by this assay ;
  • This test is not recommended for other chromosomal abnormalities(microdeletion syndrome, sexual chromosome abnormalities, other unbalanced chromosomal abnormalities)

 

Recommandations

This test must not be performed prior to 10 weeks of amenorrhea.

It does not exempt nor replace the ultrasound scan at first trimester that must be performed prior to the test for confirming the evolution of the pregnancy, precisely dating the pregnancy, measuring the nuchal translucency and identifying multiple pregnancies.


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