For the detection of CNVs in fetal cells, it is desirable to have the highest resolution possible, so that also (de novo) microdeletions/duplications are detected, such as the 2 to 3 Mb 22q11.2 deletion causing DiGeorge syndrome, the 1.5‐Mb deletion causing Williams syndrome or the 1.5‐Mb CMT1A duplication. This evidence concerns the gene PMP22 and Williams syndrome.