Tags: Clinical Utility / Clinical Experience, 2022, Turkey, RAAs, CNVs

• “Out of 593 screen-positive results, 504 (85%) were for common aneuploidies, 40 (6.7%) for rare autosomal trisomies (RATs), and 49 (8.3%) for structural chromosome anomalies (SAs). Of the screen-positives for RATs, 20 cases were evaluated only in fetal tissue, and confined placental mosaicism (CPM) could not be excluded. Among cases with definitive results (n = 20), the rates of true positives, placental mosaics, and false positives were 35%, 45%, and 10%, respectively. Among screen-positives for SAs, 32.7% were true positives. The confirmation rate was higher for duplications than deletions (58.3% vs. 29.4%). The rate of chromosomal abnormality was 10.9% in the group of 256 screen-negatives with pathological ultrasound findings.”
• Fetal growth restriction and adverse pregnancy outcomes were seen in four CPM cases (T4, T7, T16, and T22).
• “We suggest that if cfDNA testing uncovers CPM, this does not mean cfDNA testing is ‘false positive.’ The detection of CPM needs adequate laboratory work and specific genetic counseling, including backup risk for low-level true fetal mosaicism and a higher risk for poor pregnancy outcomes.”

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