Offer genetic counseling, MFM consultation, and diagnostic testing a Offer screening (MSS or NIPT) and diagnostic testing if screening was previously performed, discuss risk in context of ultrasound finding and screening result Reports for MSS include posttest risks for each assessed condition.ĬfDNA (or NIPT) screening is contraindicated MSS is less expensive and is less likely than NIPT to produce inconclusive, incidental, or no results. NIPT reports usually include posttest risks based on positive predictive value (PPV), or the likelihood that a fetus truly has the condition assessed. NIPT tests for more aneuploidies than MSS and has higher detection rates for trisomies 21 and 18. NIPT is more comprehensive and accurate than MSS. , NIPT analyzes genomic cfDNA circulating in the maternal bloodstream.īoth tests have advantages and disadvantages to consider. Noninvasive prenatal screening (NIPS) or testing (NIPT), also referred to as cell-free DNA (cfDNA) testing, was introduced more recently and is more sensitive and specific than MSS for detecting traditionally screened aneuploidies (trisomies 21, 18, and 13).
MSS measures biochemical markers present in maternal blood serum to assess a pregnant woman’s risk of having a fetus with a fetal aneuploidy or an open neural tube defect (ONTD). Maternal serum screening (MSS) has long been the standard prenatal testing option for chromosomal abnormalities. No one prenatal genetic test is superior in all situations, and clinicians and patients should understand the risks, limitations, and benefits of available testing options so that an informed choice about testing can be made. The two most common forms of testing, karyotyping and cytogenomic single nucleotide polymorphism (SNP) microarray, are the most definitive forms of prenatal genetic testing available to assess the risk for chromosome abnormalities and copy number variants in the fetus. This testing is invasive and carries a small risk of miscarriage. Prenatal genetic diagnostic testing is used to confirm whether a fetus has certain genetic disorders before birth. This topic focuses on prenatal testing for fetal aneuploidy and neural tube defects for more information on the use of laboratory tests in carrier screening for genetic disorders, see the ARUP Consult Carrier Screening for Genetic Disorders topic. Abnormal results should be followed by confirmatory prenatal genetic diagnostic testing. Like other screens, NIPT can result in false positives and false negatives, and it is not considered diagnostic. Of the two tests, cfDNA, also referred to as noninvasive prenatal screening (NIPS) or noninvasive prenatal testing (NIPT), is more sensitive and specific. In addition, MSS assesses risk for ONTDs. Maternal serum screening (MSS) and cell-free DNA (cfDNA) screening estimate a patient’s risk of carrying a fetus with a chromosomal disorder.
SEQUENTIAL TESTING PREGNANCY PROFESSIONAL
Most professional guidelines define prenatal genetic testing as encompassing two categories of testing: screening and diagnosis.
Prenatal testing is offered to all pregnant women to identify pregnancies with a chromosomal disorder, such as trisomy 21 (Down syndrome), or an open neural tube defect (ONTD).
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