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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