Limitations
A small percentage (1-2%) of pregnancies have confined placental mosaicism, where some but not all of the placental cells tested in the CVS are abnormal, even though the pregnancy is unaffected. Cells from the mother can be mixed with the placental cells obtained from the CVS procedure. Occasionally if these maternal cells are not completely separated from the placental sample, this can lead to discrepancies with the results. This phenomenon is called Maternal Cell Contamination (MCC). CVS cannot detect all birth defects. It is used for testing chromosomal abnormalities or other specific genetic disorders only if there is family history or other reason to test.
Read more about this topic: Chorionic Villus Sampling
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