In plain words
Chromosomal microarray, or CMA, is a genetic test that checks the baby's DNA for missing or extra pieces of chromosomes. It can find very small changes that a standard chromosome picture, called a , would miss. A sample can come from , , or, after birth, a blood test. Clinicians use CMA when there is a concern from an ultrasound, after a loss, or after a baby is born with a difference. Some results are clear, and some find a change whose meaning is not yet known. A genetic counselor helps families understand the result. The test does not check every gene.
The deeper version
Chromosomal microarray detects copy number variants at resolutions typically in the tens of kilobases, substantially more sensitive than karyotype for submicroscopic deletions and duplications. In prenatal diagnosis, the American College of Medical Genetics and Genomics recommends CMA as a first-tier test for fetuses with structural anomalies, and reports a diagnostic yield of roughly 6 percent beyond karyotype in anomaly-positive pregnancies (Wapner and colleagues, New England Journal of Medicine 2012). After , CMA is a recommended test in the evaluation of the cause of death. Variants of uncertain significance are reported in a notable minority of cases and require reanalysis. Exome sequencing is increasingly used as a second-tier or combined test.
Where it comes up
- Prenatal tests and ultrasounds: what each one isPregnancy: Your Body
- Termination for medical reasonsLoss and Complications
What mothers here say about chromosomal microarray
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Sources
- Wapner RJ et al. — Chromosomal microarray versus karyotyping for prenatal diagnosis. New England Journal of Medicine 2012
- American College of Medical Genetics and Genomics — Guideline: Chromosomal microarray analysis for prenatal and postnatal diagnosis, 2013