Chorionic villus sampling (CVS)

What is chorionic villus sampling (CVS)?

Chorionic villus sampling (CVS) is a diagnostic test that can be done during pregnancy. It can be done after 11 weeks of pregnancy .To do the test, a doctor will need to take a sample of cells from your placenta.

This test is used to find out if your baby has a genetic disorder or chromosomal disorder, such as Down syndrome.

CVS is a special diagnostic test. It is not offered to all pregnant women as part of routine antenatal care during pregnancy.

CVS may help you with important decisions about continuing your pregnancy. While some women are advised to have this procedure, the final choice to do so is yours.

Why might I be offered CVS?

Your doctor may recommend CVS if:

• you have had a high risk prenatal screening test result
• you already have a child with a genetic or chromosomal condition
• you will be over 35 years of age when your baby is due
• both parents are carriers of a genetic condition
• you would like certainty about a diagnosis of Down syndrome or another genetic or chromosomal condition

Ask your doctor to explain why they are offering CVS.

There is a small chance that any baby can be born with a genetic or chromosomal condition. Having a diagnostic test early in your pregnancy will give you time to consider what it means.

You may also decide to talk to a genetic counsellor.

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When is CVS done?

CVS can be done from 11 weeks of pregnancy onwards.

Who performs the CVS procedure?

CVS is performed by a specialist doctor.

Your doctor or midwife will refer you to a specialist obstetrician or women’s ultrasound service.

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How should I prepare for the CVS procedure?

Before you have the test it’s a good idea to think about why you are choosing to do it, and how you will feel once you get the results.

Talk about your options with your doctor or midwife or a genetic counsellor.

Consider who you want to discuss any important decisions with — your partner, a friend or family member. Give yourself some time to consider what the CVS results might mean.

Are there any other tests needed before having the CVS?

Your doctor will order some blood tests before you go for the CVS procedure. They will want to make sure:

• you are at least 11 weeks pregnant
• your blood group is recorded
• whether you have any infections such as hepatitis B or HIV

On the day

Ask your doctor or midwife if you need to do anything on the day to get ready for the CVS procedure.

You may need to arrive with a full bladder. You should be able eat and drink normally.

How is the CVS performed?

The procedure involves inserting a very thin needle into your placenta. This is done through your abdomen (known as a ‘transabdominal’ procedure). The needle takes a very small sample of cells from your placenta.

Your doctor will use an ultrasound scan to guide the needle, avoiding contact with your baby. The procedure itself takes only a few minutes.

You will be given local anaesthetic to numb your skin before the needle is inserted. You will be awake for the procedure.

Sometimes, if your placenta cannot be reached by inserting a needle through the abdomen, your doctor will use an alternative method. CVS can also be done by inserting a needle through your vagina and cervix (known as a ‘transcervical’ procedure).

Can having CVS harm my baby?

There is a small risk of miscarriage with every pregnancy. Having a CVS can slightly increase that overall risk.

The risk of miscarriage associated with CVS is estimated to be between 1 in 100 pregnancies.

Only a very small sample of your placenta is removed.

How will I feel after the procedure?

You will probably feel some minor discomfort. You could have cramping and period-like pain during and after CVS.

The procedure itself takes a few minutes but you may need to sit and rest for around 30 minutes before you can go home.

If you have a negative blood group, an Anti-D injection will be given after the procedure.

You might also experience some mild period-like pain on the first night after the procedure. It is safe to use regular paracetamol if you need it.

Go to your nearest hospital emergency department if after the procedure you have:

• vaginal bleeding
• severe abdominal (tummy) pain
• a high fever
• unusual discharge from your vagina

When do I get the results of my CVS?

Ask your doctor how long it will take to get your results.

You may have initial results after 1 to 2 working days. The full report can take up to 3 weeks.

What do the CVS results mean?

Prenatal diagnostic testing provides information about the health of your baby.

If CVS shows that your baby has a genetic or chromosomal condition, your doctor will probably refer you to a genetic counselling service. You can talk through how you feel about your results. Take some time to work out what it might mean for you and your family.

Testing and counselling can allow you and your family to make informed decisions such as:

• opting to end your pregnancy
• having extra monitoring during your pregnancy
• planning for how you will care for your baby

Early diagnosis of Down syndrome can help you and your doctor to check your baby for complications and to act early if needed.

How much does CVS cost?

Medicare will cover a proportion of the cost of the CVS procedure, but there may be some other costs involved. For example, if you have a private obstetrician, there may be consultation fees for the procedure.

Ask your doctor for more information about the costs involved.

Are there any alternatives to CVS?

Depending on your individual circumstances, your doctor may ask to delay diagnostic testing until you are 15 weeks pregnant. At 15 weeks you can have an amniocentesis procedure instead.

You and your doctor and midwife can decide together which tests you will have.

You will be given information about each test so that you can make an informed decision.

Questions you might want to ask your doctor

Here are some questions you might want to ask your midwife or doctor:

• Why are you offering me this test?
• What does the procedure involve, do I need to do anything on the day?
• When will I get the results?
• Who will contact me to give me the results?
• Do I need to do anything to care for myself after the procedure?

Can my partner come along too?

It’s a good idea bring your partner, or a family member or friend to your antenatal appointments. It can be useful to have someone with you for support and to chat about any information that was provided.

Check with the clinic if you can have someone with you during the CVS procedure.

Resources and support

Your GP, obstetrician or midwife can answer your questions and give you more information on CVS.

They may also refer you to a genetic counsellor who can guide you through your results. The best way to contact a genetic counsellor is to ask your doctor.

The Human Genetics Society of Australasia also has a Find a Genetic Counsellor service. It can help you find a registered counsellor in your area.