This Chromosomal Microarray (CMA) assay detects copy number changes in genomic DNA. The American College of Medical Genetics (ACMG) recommends chromosomal microarray (CMA) as the first-line genetic test for all children with autism spectrum disorders and other developmental / intellectual disabilities or birth defects (Manning et al. Gene Med 12(11):742-745, 2010). By using CMA testing, a patient’s genomic DNA is examined for gains or losses that are too small to be detected by standard G-banded chromosome studies. The increased resolution of CMA technology over conventional cytogenetic analysis allows for identification of chromosomal imbalances with greater precision, accuracy, and technical sensitivity. Therefore, this CMA assay is a more cost effective alternative to sequential or multiplex FISH for subtelomeric deletions. This CMA assay is used to detect various types and sizes of structural genomic variation in the human genome including deletions, duplications, regions of SNP homozygosity, Uniparental Disomy (UPD), and mosaicism. This CMA analysis is recommended to test patients with Mendelian conditions or syndromes, developmental delays, cognitive impairments, autism spectrum disorders, dysmorphic features, birth defects, congenital anomalies, genomic disorders and germline cancers.