Chorionic villus sampling (CVS) is a test done early in a woman’s pregnancy. CVS checks for genetic problems in your baby. During CVS, your healthcare provider takes a small piece of tissue from the placenta for testing. The placenta is an organ that grows in the uterus during pregnancy. This tissue has the same genetic material as your baby. It can show if your baby is developing problems as it grows.
Women who have a higher risk or a family history of genetic problems may want to consider CVS testing. Your healthcare provider may recommend CVS if:
You are age 35 or older
You have a family history of a genetic disorder such as Down syndrome, Tay Sachs disease, or cystic fibrosis
You and your husband are carriers for genetic disorders
Blood tests or ultrasounds during pregnancy show that your unborn baby is at increased risk of having a genetic disorder
The results of CVS are usually available earlier in pregnancy, compared with some other genetic tests, such as amniocentesis. Amniocentesis uses a needle to get samples of amniotic fluid. But CVS is not as accurate as amniocentesis. Other first trimester screening tests provide similar information to CVS, and may be used instead of CVS.
Talk about the risks and benefits of CVS with your healthcare provider. The risks of CVS include:
Infection from the procedure, or passed from mother to baby
Another risk is fetal blood mixing with the mother’s blood. This may result in the mother's immune system destroying fetal blood. This problem is called Rh factor incompatibility. Mothers are given a medicine called Rh immunoglobulin after the procedure to prevent this from happening.
Some women may not be able to have CVS. For example, if you have a vaginal infection such as herpes or gonorrhea.
CVS is usually done during the first trimester, after 10 weeks of pregnancy. Your healthcare provider will give you instructions. You will likely need a full bladder for the test. Drink plenty of water and don’t urinate before the test. You will also have an ultrasound before the test. This is a procedure that uses sound waves and a computer to make images on a screen.
The test can be done through your belly (transabdominal). Or it may be done through your cervix (transcervical). It is common to feel some cramping during and after the CVS procedure.
The healthcare provider moves a small tube (catheter) through your vagina and cervix to the uterus.
The provider uses ultrasound to guide the catheter into place near the placenta.
The provider takes a tissue sample using a tiny syringe at the end of the catheter.
The healthcare provider puts a needle through your belly (abdomen) and into the uterus.
The provider uses ultrasound to guide the needle into place near the placenta.
The provider takes a small amount of tissue with the syringe.
Women who are pregnant with several babies may need to have tissue taken from each placenta. But CVS is not always successful in women with more than one baby. This is because the position of the babies in the uterus can make it hard to get a tissue sample.
The tissue samples are sent to a lab to be checked. Early results may be available in 48 hours. Final results are usually ready in about 7 to 10 days.
After the procedure, call your healthcare provider if:
You have bleeding
You have fluid leaking from your vagina
You have cramps that are getting worse
You have a fever of 100.4°F (38°C) or higher, or as directed by your provider
Before you agree to the test or the procedure make sure you know:
The name of the test or procedure
The reason you are having the test or procedure
What results to expect and what they mean
The risks and benefits of the test or procedure
What the possible side effects or complications are
When and where you are to have the test or procedure
Who will do the test or procedure and what that person’s qualifications are
What would happen if you did not have the test or procedure
Any alternative tests or procedures to think about
When and how will you get the results
Who to call after the test or procedure if you have questions or problems
How much will you have to pay for the test or procedure. Talk to your doctor to see if you need prior authorization before getting certain prenatal genetic tests.
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