Prevalence of selected genomic deletions and duplications in a French–Canadian population-based sample of newborns

Chromosomal microarray analysis has identified many novel microdeletions or microduplications that produce neurodevelopmental disorders with a recognizable clinical phenotype and that are not observed in normal individuals. However, imbalance of other genomic regions is associated with a variable phenotype with intellectual disability (ID) or autism in some individuals but are also observed in completely normal individuals. Several large studies have reported the prevalence of copy number (CN) variants in people with particular features (e.g., ID, autism, schizophrenia, or epilepsy); few studies have investigated the prevalence of genomic CN changes in the general population. We used a high-throughput method to screen 6813 consecutive cord blood samples from a predominantly French-Canadian population to assess genomic CN in five genomic regions: 1p36, 15q11-q13, 16p11.2, 16p11.2-p12.2, and 22q11.2. We identified one deletion and one duplication within 1p36, two deletions of 15q11-q13, eight deletions of 16p11.2-p12.2, two deletions and five duplications of 16p11.2, and six duplications of 22q11.2. This study provides estimates of the frequency of CN variants in an unselected population. Our findings have important implications for genetic counseling.