Chorionic Villus Sampling (CVS)

October 6, 2011 by  
Filed under Chorionic Villus Sampling (CVS)



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What is a Chorionic villus sampling?

Chorionic villus sampling (CVS) is a procedure that is similar to amniocentesis. Instead of taking a sample of amniotic fluid, CVS takes a sample of tissue from the placenta.

The placenta has a layer of membrane called the chorion. The chorion has tiny little projections like hair that are on the membrane. These are called villi. The chorionic villi have fetal cells in them. Your doctor will take a sample of these by inserting a thin tube through your cervix or a needle through your abdomen.

When is it performed?

CVS is generally done between the 9th and 14th weeks of gestation.

CVS is generally performed in a hospital.

What Can the Results Tell You?

CVS can tell you if there are any chromosomal abnormalities such as Down syndrome or genetic disorders such as Tay Sachs and cystic fibrosis. The benefit that CVS has over an amniocentesis is that it can be done earlier in pregnancy. It can detect certain very rare genetic problems that cannot be detected with an amniocentesis.

CVS cannot detect neural tube defects such as spina bifida.

What are the Risks?

CVS is considered to be a safe procedure. CVS requires more skill than an amniocentesis, and has a slightly greater risk than amniocentesis, but this is primarily associated with inexperience of the technician.

CVS has a risk of miscarriage of 1 in 100, or 1 percent.

Vaginal bleeding occurs in 7-10 percent of patients who receive transcervical CVS. Cramping frequently occurs.

In rare cases, and infection may develop.

If you are Rh negative, it is possible for Rh sensitization to occur. To prevent this, your health care provider may give you an injection of RhIg following the procedure.

It was thought in the past that CVS could increase the chance of limb defects. Based on current research, it has been concluded that there is not an association between limb defects and CVS procedures done after 10 weeks of gestation.

How Accurate is CVS?

CVS yields a false positive in less than 1 percent of cases. A false positive indicates an abnormality when there isn’t one present.




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