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Cell-free Fetal DNA testing

What is cell-free fetal DNA testing?

Cell-free fetal DNA testing is a new screening test that indicates if a woman is at increased risk of having a fetus with Down syndrome (trisomy 21), Edward syndrome (trisomy 18), and Pateau syndrome (trisomy 13).

With this test, a sample of the woman's blood is taken after 10 weeks of pregnancy. The test measures the relative amount of free fetal DNA in the mother's blood. The test determines the chance that the fetus has Down syndrome, Edward syndrome, or Pateau syndrome based on the relative amount of DNA from chromosomes 21, 18, and 13.

The results are usually available within two weeks of the blood draw.

Does the test detect all pregnancies with Down syndrome and trisomies 18 & 13?

No. Cell-free fetal DNA testing is thought to detect greater than 99% of all Down syndrome pregnancies and greater than 98% of all trisomy 18 pregnancies. It detects about 65% of all trisomy 13 pregnancies.

What if cell-free fetal DNA testing indicates a high risk?

Women who are found to be at increased risk can have definitive testing with chorionic villus sampling (CVS) or amniocentesis.

Who can get cell-free fetal DNA testing?

At UCSF, we are currently offering the test to women who will be at least 35 years old at the time of delivery and to women who are found to be at increased risk for Down syndrome or trisomy 18 with standard screening tests.

The accuracy of the test has not been studied in low-risk women and is not designed for use in women with multiple pregnancies (such as twins), or in women with egg donor pregnancies.

Is cell-free fetal DNA testing covered by insurance?

This test is not standard of care and is considered investigational by some insurance companies. Since coverage varies based on individual plans, it may not be


For more information:

If you have additional questions about cell-free fetal DNA testing, please feel free to contact one of our genetic counselors at the UCSF Prenatal Diagnostic Center. To talk with a genetic counselor or to schedule an appointment, please call (415) 476-4080.

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