Abstract
ObjectiveThe aim of this study is to understand the diagnostic utility of comparative genomic hybridization (CGH)-based microarrays for pregnancies with abnormal ultrasound findings.MethodsWe performed a retrospective analysis of 2858 pregnancies with abnormal ultrasounds and normal karyotypes (when performed) tested in our laboratory using CGH microarrays targeted to known chromosomal syndromes with later versions providing backbone coverage of the entire genome. Abnormalities were stratified according to organ system involvement. Detection rates for clinically significant findings among these categories were calculated.ResultsClinically significant genomic alterations were identified in cases with a single ultrasound anomaly (n = 99/1773, 5.6%), anomalies in two or more organ systems (n = 77/808, 9.5%), isolated growth abnormalities (n = 2/76, 2.6%), and soft markers (n = 2/77, 2.6%). The following anomalies in isolation or with additional anomalies had particularly high detection rates: holoprosencephaly (n = 9/85, 10.6%), posterior fossa defects (n = 21/144, 14.6%), skeletal anomalies (n = 15/140, 10.7%), ventricular septal defect (n = 14/132, 10.6%), hypoplastic left heart (n = 11/68, 16.2%), and cleft lip/palate (n = 14/136, 10.3%).ConclusionsMicroarray analysis identified clinically significant genomic alterations in 6.5% of cases with one or more abnormal ultrasound findings; the majority were below the resolution of karyotyping. Larger data sets such as this allow for sub-stratification by specific anomalies to determine risks for genomic alterations detectable by microarray analysis. © 2012 John Wiley & Sons, Ltd.
Highlights
Invasive prenatal testing is used mainly to identify chromosome abnormalities in the fetus
The chance of finding a cytogenetic aberration depends on many factors, including family history of a chromosome abnormality, the age of the mother, and whether fetal anomalies are identified by ultrasound
The recent utilization of microarray analysis in prenatal testing allows for estimates of the frequency of identifying clinically significant copy number alterations (CNAs) by microarray analysis that are not detected by routine fetal karyotyping
Summary
Invasive prenatal testing is used mainly to identify chromosome abnormalities in the fetus. Several studies have attempted to stratify the risk of a chromosome abnormality based on the specific fetal anomalies identified.[1,2,3,4,5,6] Over all anomalies identified, the chance of finding an abnormal fetal karyotype ranged in these studies from ~9% to ~19%; the majority were aneuploidies and triploidies After excluding these classes, the remaining chromosome abnormalities identified in one study (~28% of the total abnormal karyotypes) were marker chromosomes, Prenatal Diagnosis 2012, 32, 986–995 large deletions, and unbalanced translocations.[1] In another study,3 19.2% of fetuses (412/2143) had chromosomal abnormalities identified by conventional chromosome analysis, with the total number of non-aneuploid, abnormal fetal karyotypes at 1.2% of all cases studied and 6% of all abnormal karyotypes found. The recent utilization of microarray analysis in prenatal testing allows for estimates of the frequency of identifying clinically significant copy number alterations (CNAs) by microarray analysis that are not detected by routine fetal karyotyping
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