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 Patau 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 Patau 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.
No. Cell-free fetal DNA testing is thought to detect greater than 99 percent of all Down syndrome pregnancies and greater than 98 percent of all trisomy 18 pregnancies. It detects about 65 percent of all trisomy 13 pregnancies.
At UCSF, we currently offer 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 cell-free fetal DNA testing has not been validated in low-risk women. UCSF is participating in a study to establish the accuracy of the test in the general population.
Cell-free fetal DNA testing is not designed for use in women with multiple pregnancies such as twins, or in women with egg donor pregnancies.
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 covered.
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, call (415) 476-4080.
Reviewed by health care specialists at UCSF Medical Center.
This information is for educational purposes only and is not intended to replace the advice of your doctor or health care provider. We encourage you to discuss with your doctor any questions or concerns you may have.
Prenatal Diagnostic Center
1825 Fourth St., Third Floor
San Francisco, CA 94158
Phone: (415) 476-4080
Fax: (415) 353-4077