Editing Chorionic villus sampling (section)

==Limitations==
A small percentage (1-2%) of pregnancies have [[confined placental mosaicism]], where some but not all of the [[placenta]]l cells tested in the CVS are abnormal, even though the pregnancy is unaffected.<ref name="Wapner">{{Cite journal |last=Wapner |first=Ronald J. |year=2005 |title=Invasive Prenatal Diagnostic Techniques |journal=Seminars in Perinatology |volume=29 |issue=6 |pages=401–4 |doi=10.1053/j.semperi.2006.01.003 |pmid=16533654}}</ref> Cells from the mother can be mixed with the [[placenta]]l cells obtained from the CVS procedure. Occasionally if these maternal cells are not completely separated from the [[placenta]]l sample, this can lead to discrepancies with the results.  This phenomenon is called Maternal Cell Contamination (MCC).<ref name=Wapner/>  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.{{citation needed|date=August 2015}}