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Poster Session I Thursday, January 26 • 10:30 AM - 12:00 PM • Octavius Ballroom| Volume 216, ISSUE 1, SUPPLEMENT , S128, January 01, 2017

199: ACOG and SMFM recommendations for prenatal diagnosis: is karyotyping really sufficient?

      Objective

      ACOG and SMFM recommend the use of chromosomal microarray analysis (CMA) in prenatal diagnosis for cases with one or more structural abnormality detected by ultrasound. For patients with a structurally normal fetus, invasive testing by either microarray or karyotype is recommended. We evaluated CMA results for cases that could be clinically grouped into the two recommended categories and aimed to specifically determine how many clinically significant chromosome abnormalities would not have been detected if evaluated solely by karyotype analysis following the recommendations.

      Study Design

      A total of 3225 prenatal samples evaluated over a three year period by single nucleotide polymorphism (SNP) array were analyzed. Cases were categorized into two groups: those that met ACOG guidelines for array testing versus those that met ACOG guidelines for karyotype or array. CMA results for each group were classified as: normal, abnormal or VOUS.

      Results

      Of the 3225 cases analyzed, 1476 (45.8%) met ACOG recommendations for CMA and 1749 (54.2%) for either CMA or karyotype. For the CMA group, 258 (17.5%) had abnormal results, 1149 (77.8%) normal results and 69 (4.7%) VOUS results. Notably, of the 258 with abnormal results, 78 (5.28% of the total cases) would not been detected by karyotype. In the CMA or karyotype group, 156 (8.9%) had abnormal results, 1498 (85.7%) normal results and 95 (5.4%) VOUS results. Of the 156 abnormal CMA cases, 45 (2.6% of the total cases) would not have been detected solely by karyotype analysis.

      Conclusion

      This study suggests that at least 2.6% of cases with abnormal CMA results including microduplications/deletions, uniparental isodisomy and mosaic abnormalities would have been missed by karyotype analysis following ACOG recommendations. This is significant and reinforces the profound value and diagnostic utility in performing microarray in place of karyotype for pregnancies undergoing invasive testing regardless of the presence of a structural fetal abnormality.