Noninvasive Prenatal Testing: A New Genetic Screening Tool for Use by Pregnant Women
During the past six years, advances in genetic technology completely have changed the way women and their health-care providers approach genetic testing during pregnancy.
Noninvasive prenatal testing (NIPT), one of the newest additions in genomic testing, is a simple blood test that can tell a lot about a baby’s likelihood of having certain genetic conditions.
During pregnancy, the placenta sheds cells into the mother’s bloodstream. Eventually, these cells die, and the DNA contained in those placental cells – DNA very similar to that from the fetus – is released into the mother’s blood and mixes with maternal DNA. NIPT, also known as noninvasive prenatal screening (NIPS) or prenatal cell-free DNA screening, is a new prenatal screening technique that uses high-throughput DNA sequencing to analyze this small fraction of the baby’s DNA present in the mother’s blood sample.
“Noninvasive prenatal testing is a great screening tool that can be performed earlier than other screening or diagnostic tools and is less invasive than other tests used to diagnose prenatal genetic conditions,” says Leslie Benson, MS, CGC, prenatal genetic counselor in the Department of Obstetrics and Gynecology at Banner – University Medical Center Tucson and a member of the UA’s Center for Applied Genetics and Genomic Medicine.
Since 2012, NIPT has been used to screen for certain chromosomal conditions in a developing baby. These conditions, called aneuploidies, occur when a baby has an incorrect number of chromosomes. NIPT typically screens for Down syndrome, trisomies 18 and 13, and also can flag cases in which the baby may have an incorrect number of sex chromosomes. In addition, NIPT can reveal the sex of the baby.
While there are numerous benefits to this type of testing, including lowering the number of invasive tests performed on low-risk pregnancies, the test does have some limitations. “While NIPT has really expanded the use of genetic testing in prenatal care, it’s important to remember that it can’t tell us everything,” says Ms. Benson. “No test can guarantee a perfectly healthy baby.”
NIPT is a screening test, not a diagnostic. It can be used to flag women who may have a higher risk of having a baby with one or more of the chromosomal abnormalities for which it tests. It cannot be used alone to tell whether a baby definitively has a certain condition. If you have received a normal result through NIPT, it is important to continue with standard prenatal care, including scheduled ultrasound exams and doctor visits. If you have received a positive result on NIPT, you can discuss options for diagnostic testing with your physician or with a genetic counselor.
Researchers continue to expand this technology to tackle other health-care problems. For example, ongoing research is identifying ways that high-throughput DNA sequencing can be applied to liquid biopsies, in which DNA from a simple blood or urine sample is analyzed to detect, monitor and identify cancers or help improve the precision of targeted therapies. Just as NIPT has revolutionized prenatal genetic testing, and may become the standard of care, researchers in this field are confident that continued advances in DNA sequence analysis will continue to transform other areas of medicine.