12 Having specific measurement guidelines helps maintain the detection rate of Down syndrome. Measuring nuchal translucency requires specialized training and certification to learn the standardized technique. 11 The measurement is gestational-age dependent on average, it increases 15 to 20 percent per week. Nuchal translucency refers to an ultrasonographic sonolucency in the posterior fetal neck. Protein produced by the placenta and the fetal liver low levels associated with Down syndrome Nuchal translucency testing and measurement of PAPP-A and hCG are used to determine risk if at increased risk, proceed directly to invasive testing if not at increased risk, a second calculation with the addition of the quadruple screen produces another risk determination Zinc-binding protein that acts as an enzyme low levels associated with increased risk of Down syndrome Thickness of the fluid under the skin of the fetal neck, measured by ultrasonography Plasma protein found in mother’s blood that is produced by the fetal liver elevated levels associated with open neural tube defects, older than expected fetus (i.e., dating error), or multiple gestations low levels associated with Down syndrome Nuchal translucency testing and measurement of PAPP-A and hCG are integrated with the quadruple screen to produce a single risk result Hormone produced by the placenta high levels associated with increased risk of Down syndrome Hormone made from the fetal part of the placenta elevated levels associated with increased risk of Down syndrome Nuchal translucency, PAPP-A, and hCG measurements are used to determine risk no further testing is recommended in women at low risk of Down syndrome maternal serum AFP should be performed in the second trimester to assess risk of neural tube defects Nuchal translucency testing and serum screening can be performed in multiple gestations, but they are less sensitive than first-trimester screening in singleton gestations.Ĭombination of nuchal translucency testing, serum measurement of PAPP-A and free or total hCG, and maternal age Women who pursue first-trimester screening alone should be offered maternal serum AFP testing in the second trimester to screen for neural tube defects. Genetics counseling and chorionic villus sampling or amniocentesis should be offered to all women with elevated risk, as determined by serum screening. Women with isolated nuchal thickening or isolated maternal serum AFP (with normal ultrasonography and normal karyotype) should be followed closely because they are at increased risk of poor pregnancy outcomes.Ĭombined first- and second-trimester screening offers superior detection rates while maintaining low false-positive rates. Quadruple screening is recommended for second-trimester screening. Pregnant women should be offered screening and invasive diagnostic testing regardless of age.Ĭombined testing is recommended for first-trimester screening. Specific screening tests will depend on availability of the procedure and patient preference. Comprehensive counseling should be available to all pregnant women. For women who do not present until the second trimester, the quadruple screen is recommended. If nuchal translucency testing is unavailable, the maternal serum-integrated test is safest and most effective. An integrated test with nuchal translucency testing is the most effective method for women who present in the first trimester. These options include an analysis of pregnancy-associated plasma protein A, with or without nuchal translucency testing, in combination with quadruple screening. Patients may also choose a combination of first- and second-trimester screening in an integrated, stepwise sequential, or contingent sequential fashion. Screening options in the second trimester include serum screening using triple or quadruple screening, and ultrasonography. Nuchal translucency testing alone is not as effective. Screening options in the first trimester include nuchal translucency testing in combination with measurement of pregnancy-associated plasma protein A and human chorionic gonadotropin. Diagnostic options include chorionic villus sampling in the first trimester and amniocentesis in the second trimester. New developments in screening methods have increased the number of options for patients. Pregnant women of all ages should be offered screening and invasive diagnostic testing for chromosomal abnormalities before 20 weeks’ gestation.
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