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Intervention:
Chorionic villus sampling
Gray31.png
Model of human embryo 1.3 mm. long. (Villi of chorion labeled at lower right.)
ICD-10 code: 16603-00
ICD-9 code: 75.33
MeSH D015193
Other codes:

Chorionic villus sampling (CVS) is a form of prenatal diagnosis to determine chromosomal or genetic disorders in the fetus. It entails getting a sample of the chorionic villus (placental tissue) and testing it. CVS can be carried out 10-13 weeks after the last period, earlier than amniocentesis (which is carried out as early as 14-16 weeks). It is the preferred technique before 15 weeks.[1]

Use as early as 8 weeks in special circumstances has been described.[2]

It can be performed in a transcervical or transabdominal manner.[3]

Contents

Indications

Possible reasons for having a CVS can include:

Risks

CVS carries a higher risk of harming the fetus than amniocentesis (miscarriages occur in around 1 in 100 to 1 in 200 cases with CVS, versus around 1 in 1,600 with amniocentesis[4]). Apart from a risk of miscarriage, there is a risk of infection and amniotic fluid leakage. The resulting amniotic fluid leak can develop into a condition known as oligohydramnios which is low amniotic fluid level. If the resulting oligohydramnios is not treated and the amniotic fluid continues to leak it can result in the baby developing hypoplastic lungs (underdeveloped lungs). Additionally, there is a risk of CVS causing digit-reduction defects in the fetus if performed before 11 weeks (0.07%-0.10%).[5]

It is important after having a CVS that the OB/GYN follow the patient closely to ensure the patient does not develop infection.

Limitations

A small percentage (1-2%) of pregnancies will have confined placental mosaicism, where some but not all of the placental cells tested in the CVS will be abnormal, even though the pregnancy is unaffected.[6] 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).[6] CVS can not detect all birth defects. It's used for testing chromosomal abnormalities or other specific genetic disorders only if there is family history or other reason to test.

See also

References

External links

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