Chorionic Sampling Villus

March 17 19:59 2019 Print This Article

Chorionic Sampling Villus is a method of obtaining foetal cells for chromosome and gene examination. Chorionic villus sampling (CVS) is done by passing a slender tube through cervical canal into the uterus and using gentle suction to withdraw a fragment of the outer membrane (chorion) of the amniotic sac, which contains the foetus and its surrounding fluid. A sample can also be obtained by passing a fine needle into the uterus through the abdominal and uterine walls. Both procedures are performed with ULTRASOUND guidance

Because more foetal cells are obtained via CVS than from AMNIOCENTESIS, they can be examined immediately or after a short period of culture. Results are usually available within 10 days or sooner. CVS can be performed from the ninth week of pregnancy. The earlier diagnosis of genetic abnormalities in CVS than in amniocentesis allows termination of pregnancy, if chosen, by suction aspiration abortion, which is safer than induced labour. The test is not suitable for diagnosis of spina bifida

The risk of miscarriage after CVS through the cervix is about 3 in 100 (slightly fewer if it is performed through the abdomen, as in amniocentesis), This is less than 1 per cent higher than the risk of miscarriage at 10 weeks among women who have not had CVS.

Chorionic villus sampling is done at, or after, ten weeks of pregnancy. Occasionally, it can be done earlier, but the risk of miscarriage is higher. There are two ways to perform chorionic villus sampling: through the cervix and through the abdomen. Chorionic villus sampling does not detect neural tube defects. If neural tube defects or Rh incompatibility are a concern, an amniocentesis will be performed. Chorionic villus sampling detects chromosome abnormalities and genetic disorders. Risks associated with CVS include miscarriage, birth defects, rupture of the amniotic sac, uterine infection, and bleeding. This test is different from amniocentesis in that it does not allow for testing for neural tube defects. The test might be offered if your baby has an increased risk of a specific chromosomal or genetic disorder. In other cases, chorionic villus sampling may be recommended if the results of a screening test in the first trimester cause concern. Chorionic villi are formed from the fertilized egg, so they have the same genes as the baby. Some women say CVS doesn’t hurt at all; others experience cramping or a pinch when the sample is taken.

How to prepare for the test?

  • Genetic counseling is recommended prior to the procedure. This will allow you to make an unhurried, informed decision regarding options for prenatal diagnosis.
  • You may be asked to drink a glass of fluid about an hour before the test so that your bladder is full. A full bladder makes it easier to do the test.
  • You will be asked to sign a consent form before this procedure, and you may be asked to wear a hospital gown.
  • Be sure to tell your doctor if you are allergic to any medicines, such as numbing medicines, before the procedure.

Why the test is performed?

  • This test is a way of detecting congenital (present from before birth) defects.
  • The sample is used to study the DNA, chromosomes, and enzymes of the fetus and can be done earlier than amniocentesis, about 10 to 12 weeks after your last menstrual period.
  • Fragile X syndrome, and other conditions causing mental health problems.
  • Chorionic villus sampling does not detect neural tube defects. If neural tube defects or Rh incompatibility are a concern, an amniocentesis will be performed.

What are the side effects to the mother or baby?

  • Excessive bleeding.
  • Spotting.
  • Cramping and pain at puncture point.
  • Chills.
  • Excessive discharge.
  • Leaking of amniotic fluid.

What the risks are?

Possible complications include the following:

  • Rh incompatibility in the mother.
  • Rupture of membranes (rupture of the amniotic membrane).
  • Infection.
  • Heavy cramping, or bleeding, after the CVS has been performed.
  • In very rare cases, your baby may be damaged during the CVS – clinical trials have made an association between CVS and a slightly increased risk for limb abnormalities in the foetus, however, these are not conclusive.
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