The use of chromosome microarray analysis as a first-line test in low risk pregnancies

OBJECTIVE: To assess the feasibility of offering array-based comparative genomic hybridizationtesting for prenatal diagnosisas a first-line test, a prospective study was performed, comparing the results achieved from array comparative genomic hybridization(aCGH) with those obtained from conventional karyotype. METHOD: Women undergoing amniocentesisor chorionic villus samplingwere offered aCGH analysis. A total of 1037 prenatal samples were processed in parallel using both aCGH and G-bandingfor standard karyotyping. Specimen types included amniotic fluid (89.0%), chorionic villus sampling(9.5%) and cultured amniocytes(1.5%). RESULTS: Chromosomal abnormalitieswere identified in 34 (3.3%) samples; in 9 out of 34 cases (26.5%) aCGH detected pathogenic copy number variationsthat would not have been found if only a standard karyotypehad been performed. aCGH was also able to detect chromosomal mosaicism at as low as a 10% level. There was complete concordance between the conventional karyotypingand aCGH results, except for 2 cases that were only correctly diagnosed by aCGH. CONCLUSIONS: This study demonstrates that aCGH represents an improved diagnostic tool for prenatal detection of chromosomal abnormalities. Although larger studies are needed, our results provide further evidence on the feasibility of introducing aCGH as a first-line diagnostic test in routine prenatal diagnosispractice.