What you can expect

Prenatal cell-free DNA screening can be done as early as week 10 of pregnancy.

During the procedure

During prenatal cell-free DNA screening, a maternal blood sample is taken and sent to a lab. The lab analyzes the maternal and fetal DNA in the blood sample. A higher than expected ratio of chromosome 21 sequences indicates, for example, the likely presence of trisomy 21 in the fetus. Trisomy 21 is the most common cause of Down syndrome.

Typically, test results are available within two weeks.

April 12, 2017
  1. AskMayoExpert. Prenatal cell-free DNA screening. Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2016.
  2. American College of Obstetricians and Gynecologists Committee on Genetics and the Society for Maternal-Fetal Medicine. Committee Opinion No. 640: Cell-free DNA screening for fetal aneuploidy. Obstetrics & Gynecology. 2015;126:e31.
  3. Allyse M, et al. Non-invasive prenatal testing: A review of international implementation and challenges. International Journal of Women's Health. 2015;7:113.
  4. Society for Maternal-Fetal Medicine Publications Committee. #36: Prenatal aneuploidy screening using cell-free DNA. American Journal of Obstetrics and Gynecology. 2015;212:711.
  5. Prenatal cell-free DNA screening. National Society of Genetic Counselors. http://www.acog.org/Resources-And-Publications/Endorsed-Documents. Accessed Jan. 18, 2017.
  6. Palomaki GE, et al. Prenatal screening for common aneuploidies using cell-free DNA. http://www.uptodate.com/home. Accessed Jan. 17, 2017.
  7. Gregg AR, et al. Noninvasive prenatal screening for fetal aneuploidy, 2016 update: A position statement of the American College of Medical Genetics and Genomics. Genetics in Medicine. 2016;18:1056.

Prenatal cell-free DNA screening