Cells from your baby are looked at carefully for the proper number and arrangement of the genetic material (chromosomes) that show genetic diseases. Normally there are 46 chromosomes in each cell, arranged in 23 pairs. Chromosomes also tell the sex of your baby. It may take 1 to 2 weeks to get CVS results.
Chorionic villus sampling (CVS)
No abnormalities are found in the genetic material of the chorionic villus cells.
Abnormalities are found in the genetic material of the chorionic villus cells.
What Affects the Test
In rare cases, the chorionic villus cells may have abnormal genetic material even though the baby's cells are normal. This is called a false-positive result. An abnormal test result may need to be confirmed by amniocentesis.
What To Think About
Normal results from chorionic villus sampling (CVS) do not guarantee that your baby will be healthy. CVS can't find neural tube defects.
Amniocentesis (which is usually done later in the pregnancy than CVS) can also be used to find other diseases of the fetus, such as neural tube defects. If CVS does not show clear results, amniocentesis may need to be done.
CVS is done if you are at high risk for having a baby with a chromosomal birth defect (such as Down syndrome) or a family genetic disease (such as Tay-Sachs disease or hemophilia). The benefits of this test often outweigh the risks. Genetic diseases and birth defects can be found earlier in pregnancy by CVS than by amniocentesis. This allows you to make an earlier decision whether to continue or end the pregnancy.
The results of CVS may vary depending on how the sample was taken.
CVS causes bleeding that could lead to mixing of your blood and your baby's about half of the time. If you have Rh-negative blood, you will be given the Rh immunoglobulin vaccine (such as RhoGAM) to prevent Rh sensitization which could harm your baby if he or she has Rh-positive blood.