Compare karyotype and CMA in prenatal testing: what does each detect?

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In prenatal testing, the two methods differ in what kinds of chromosome changes they can reveal. Karyotype analyzes chromosomes under a microscope to look at their number and structure, so it can detect aneuploidies (extra or missing chromosomes) and balanced rearrangements (such as translocations or inversions where there is no net gain or loss of genetic material). Chromosomal microarray (CMA), on the other hand, examines DNA to find copy-number variants across the genome, identifying smaller deletions or duplications that karyotype would miss. Because balanced rearrangements do not involve a change in copy number, CMA cannot detect them.