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Chromosome Analysis, Chorionic Villus Sample

Test code(s) 14592X

This is an outdated version of this FAQ. It was effective 09/12/2012 to 05/20/2015.

The current version is available here.

Question 1. Multiple fetal anomalies were detected on ultrasound, but the chromosome analysis was normal. Are there further genetic studies that can be done to evaluate the fetal anomalies?

Yes, there are other studies that may be appropriate. There are many causes of fetal anomalies, some of which are genetic. In the absence of clinical suspicion for a specific genetic disorder, a microarray analysis may be performed on the chorionic villus sample to detect subtle deletions and duplications (test code 90927, Chromosomal Microarray, Prenatal, ClariSure® Oligo-SNP). If clinical suspicion exists for a specific disorder, there may be other genetic testing available. Please contact 1-866-GENE-INFO to discuss the case with a genetic counselor and for information on adding another test.

Question 2. My patient has a personal or family history of a chromosome abnormality. Prenatal chromosome analysis was reported as normal. Does this result guarantee the fetus doesn’t have the familial chromosome abnormality?

No, please call 1-866-GENE-INFO to discuss this case with a genetic counselor. Documentation of the specific genetic abnormality in the family will be necessary to determine the accuracy of the testing that was performed on the fetus.

Question 3. Which chromosome abnormalities does this assay rule out?

This assay rules out:

  • Trisomies such as Down syndrome, trisomy 18, and trisomy 13
  • Sex chromosome abnormalities such as Turner syndrome and Klinefelter syndrome
  • Most rearrangements, including Robertsonian translocations and inversions
  • Marker chromosomes
  • Mosaicism above 14% (at a 95% confidence level)

Question 4. Which disorders cannot be detected by this assay?

This assay cannot detect:

  • Most microdeletion syndromes, including DiGeorge, Prader-Willi, Angelman, Williams, and Smith-Magenis
  • Mosaicism below 14% (at a 95% confidence level)
  • Fragile X syndrome
  • Single gene disorders such as cystic fibrosis, Marfan syndrome, neurofibromatosis, etc.
  • Disorders associated with small cryptic (not microscopically visible) gains or losses or genetic material

Question 5. The report indicates that maternal cell contamination (MCC) cannot be ruled out. Is there a test that can be done to evaluate for MCC?

Yes. Maternal Cell Contamination Study, STR Analysis (test code 10262) can be used to test maternal blood samples. Ideally, the maternal sample should be submitted with the prenatal sample. If you are considering adding Maternal Cell Contamination Study, STR Analysis to a completed prenatal case, please call 1-866-GENE-INFO to speak with a genetic counselor.

This FAQ is provided for informational purposes only and is not intended as medical advice. A physician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.

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