Cell-free Fetal DNA for Fetal Chromosome Disorders
Also known as: Noninvasive prenatal testing (NIPT) or noninvasive prenatal diagnosis (NIPD)
Cell-free fetal DNA (cffDNA) testing is a non-invasive maternal blood test that can assess the risk of a pregnant woman's developing baby (fetus) having certain chromosome disorders early in pregnancy. The test requires only a blood draw from a pregnant woman's arm. The blood sample is evaluated for fetal cell-free genetic material that circulates in the mother's blood.
Currently, the test primarily screens for three disorders in a developing baby resulting from the presence of an extra chromosome (trisomies): Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Patau syndrome (trisomy 13). It may also be used to identify other rare conditions resulting from an extra chromosome or missing piece of chromosome (microdeletion).The cffDNA test can be done as early as the 10th week of pregnancy, with results available in about one week.
Studies of cffDNA have shown an ability to recognize 98% of cases of Down syndrome, with a false-positive rate of less than 0.5%, although these studies were among high-risk women only. The current first trimester screen only assesses risk of Down syndrome and Edwards syndrome, whereas cffDNA screens for three trisomy disorders with the potential for more.
The American College of Obstetricians and Gynecologists (ACOG) released a position statement in December 2012 calling the new test highly accurate for screening but not for diagnosis. For now, ACOG says cffDNA testing should be offered, after pre-test genetic counseling, only to pregnant women at increased risk. They include women age 35 and older, women with a history of a pregnancy with a child with a trisomy, and women carrying a fetus with ultrasound findings indicating increased risk. Women with positive cffDNA results should be referred for genetic counseling and be offered chorionic villi sampling (CVS) or amniocentesis to confirm the diagnosis.
ACOG says that the test should not be offered to low-risk women because it has not been sufficiently tested in this group. The International Society for Prenatal Diagnosis and the National Society of Genetics Counselors have released similar statements. Additional research may eventually provide evidence of the test's usefulness in low-risk pregnant women.