Cell Free Fetal DNA in Non-Invasive Prenatal Molecular Screening
thesisposted on 2020-05-01, 00:00 authored by Christopher K. Henry
Prenatal genetic diagnostic testing methods are commonly used for high-risk pregnancies in order to gain information about the embryo or fetus. There are many different technologies that can be used for prenatal testing, each which comes with its own advantages and disadvantages. One screening method that is becoming increasingly reliable is cell free fetal DNA (cffDNA) testing. The cffDNA screen analyzes fetal DNA that is present in the maternal bloodstream during a pregnancy. This cffDNA can be separated from other blood components and sequenced, which will then provide information about the likelihood of a fetus having a chromosomal abnormality or a single gene disorder. There are three main DNA sequencing methods: Massively Parallel Shotgun Sequencing (MPSS), Digital Analysis of Specific Regions (DANSR), and Single Nucleotide Polymorphism (SNP)-based sequencing. The cffDNA screening method has very high accuracy for detecting abnormal numbers of chromosomes (aneuploidies), specifically the three copies of chromosome 21 in Down syndrome, for which this screening method is the most accurate non-invasive prenatal test. Benefits of cffDNA screening include that it is non-invasive and has a zero chance of increasing the risk of spontaneous termination of a fetus, a risk that is more of a concern for invasive prenatal diagnostic procedures such as chorionic villus sampling and amniocentesis. The accuracy of the cffDNA screen will continue to improve as technologies progress; but until that time, it is best used as a preliminary screen with positive results followed by invasive testing procedures if desired.