The triple screen finds abnormalities caused by aneuploidy by testing for human chorionic gonadotropin, unconjugated estriol and alpha-fetoprotein, three chemicals found in the maternal serum. The quadruple screen tests for the same chemicals with the addition of inhibin A (Farrell). These tests are examples of maternal serum alpha-fetoprotein screening that can be done on “all pregnant women, regardless of their risk of having a baby with Down syndrome or neural tube defects, serious malformations of the brain and spine” with the exception of women experiencing multiple pregnancy (Press 75, Brody). Maternal serum alpha-fetoprotein screening uses a sample of the pregnant woman’s blood for the testing, but does not make use of the cfDNA found in the blood (Press, Rothaus).
Noninvasive prenatal testing using maternal serum has developed since the triple and quadruple screening tests were established in the late 1980s and early 1990s. “First trimester aneuploidy screening is a new screening approach consisting of an assessment of maternal serum markers in conjunction with the sonographic measurement of the back of the fetal neck” (Farrell 5). This procedure can be done “as early as eleven weeks into gestation,” and gives information that is similar to that given by the triple and quadruple screening tests, which cannot be completed until after fifteen weeks of gestation (Farrell 5).
New technology in noninvasive prenatal genetic screening tests has proven quite successful in determining the likelihood of a genetic malformation. These highly accurate tests “work by using a sample of cell-free fetal DNA circulating in the mother’s blood,” which can be collected as early as five to seven weeks into gestation “to detect chromosomal conditions” (Darnovsky and Stern, Norwitz and Levy).
The number of noninvasive prenatal genetic tests available continues to grow as science advances. Commercial noninvasive prenatal testing is done in the United States by multiple companies, including the Sequenom Center for Molecular Medicine and Verinata Health, which both use targeted sequencing of cfDNA to look at areas of interest, such as chromosomes “13, 18, 21, X and Y” (Norwitz and Levy). Some other brands of commercial tests utilize massively parallel signature sequencing, known as MPSS, to rapidly sequence a high volume of DNA to create a picture of the entire genome (Norwitz and Levy, "Massively Parallel Signature Sequencing (MPSS)").
The benefits of noninvasive prenatal testing include the availability of test results early in pregnancy, a procedure to collect maternal blood for testing that features no risk of miscarriage, and highly accurate results. Over ninety-nine percent of positive results from noninvasive prenatal testing of cfDNA are true positives. A study conducted in the United Kingdom found no false positives or false negatives, and all genders were correctly determined when results from noninvasive testing of cfDNA were compared...