Noninvasive prenatal diagnosis using Cell free fetal DNA in maternal blood: Current efforts and future perspectives
Cell-free fetal DNA (cffDNA) is fetal DNA circulating freely in the maternal blood stream. cffDNA can first be observed as early as seven weeks gestation, and the amount of cffDNA increases as the pregnancy progresses. cffDNA originates from the trophoblast making up the placenta. Analysis of cffDNA provides a method of non-invasive prenatal diagnosis. Maternal blood sample is collected after 10 weeks of pregnancy but can be detected as early as the fifth week. The test measures the relative amount of free fetal DNA in the mother’s blood. A variety of methods have been used for mutation detection in fetal DNA. Millions of small fragments of cffDNA from maternal plasma are amplified and sequenced. After the fragments are mapped to the human genome and analyzed for frequency/density along each chromosome, fetal Down syndrome and a variety of other chromosomal abnormalities can be detected with a high degree of accuracy for families at high risk for inherited genetic disorders. In industrialized countries, cffDNA tests are now routinely being offered to RhD-negative patients at increased risk of isoimmunization. cffDNA concentration can also be used as a screening tool for preeclampsia. The high degree of accuracy of cffDNA as a method of noninvasive prenatal testing during pregnancy carries a number of socio-ethical implications when it is used for early detection fetal sex for suspected X-linked diseases. It is important for women to receive detailed pretest counseling that explains the benefits and limitations of the test.