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Non-invasive prenatal testing for trisomies

ACOG and SMFM also jointly published a committee opinion stating that noninvasive prenatal screening using cfDNA from the plasma of pregnant women offers potential as a screening method for fetal aneuploidy. A number of laboratories have validated different techniques and all tests have a high sensitivity and specificity for trisomy 18 and trisomy 21, regardless of which molecular technique is used. Women whose results are not reported, indeterminate or uninterpretable should receive further genetic counseling and be offered comprehensive ultrasound evaluation and diagnostic testing because of an increased risk of aneuploidy. Patients should be counseled that cfDNA screening does not replace the precision obtained with diagnostic tests, such as CVS or amniocentesis and, therefore, is limited in its ability to identify all chromosome abnormalities. The cfDNA screening test should not be considered in isolation from other clinical findings and test results. Management decisions should not be based on the results of the cfDNA screening alone. Patients should be counseled that a negative cfDNA test result does not ensure an unaffected pregnancy. Given the performance of conventional screening methods and the limitations of cfDNA screening performance, conventional screening methods remain the most appropriate choice for first-line screening for most women in the general obstetric population. Screening for microdeletions has not been validated in clinical studies, and the true sensitivity and specificity of this screening test is uncertain. Routine cfDNA screening for microdeletion syndromes should not be performed. (ACOG, 2015)