Chorionic Villus Sampling Cvs

Overview

Chorionic villus sampling (CVS) is a test you can have in early pregnancy. It takes a tiny sample of cells from the placenta — the tissue that feeds your baby — and checks them for certain genetic and chromosomal conditions, such as Down's syndrome. Chromosomes are the packages of instructions inside our cells, and genes are the individual instructions within them. CVS is a diagnostic test, which means it can tell you with high accuracy whether your baby has a particular condition, rather than just how likely it is. It is not a routine test. You would only be offered it if there is a reason to think your baby has a higher chance of one of these conditions.

CVS is not a routine test. Most pregnancies don't need it. It is offered to a small number of people each year — those who have been told their baby has a higher chance of a chromosomal or genetic condition.

Anyone who is pregnant and has been told their baby has a higher chance of a genetic or chromosomal condition. That might be because a screening test showed a higher chance, because of a family history, because a scan showed something unusual, or because you or your partner are known to carry a gene for a condition.

Symptoms

Common symptoms

• Mild cramping, a bit like period pain, during the test and for a day or so afterwards.
• A small amount of light bleeding or spotting from the vagina — this is common in the first day or two.
• Some bruising or soreness where the needle went in, if the sample was taken through your tummy.
• Feeling tired or emotional afterwards — the waiting and the decisions can be draining.

Symptoms in children

• Not applicable — CVS is only done during pregnancy and is not a test for children.
• The sample comes from the placenta, not directly from your baby.

Symptoms in older adults

• Not applicable — CVS is only done during pregnancy.

Causes

Main causes

• CVS is a test, not a condition, so it doesn't have a cause. Here is why it might be offered:
• A pregnancy screening test (a blood test and/or scan) showed a higher chance of a chromosomal condition such as Down's, Edwards' or Patau's syndrome.
• A previous pregnancy or baby was affected by a genetic or chromosomal condition.
• You or your partner are known to carry a gene for a condition such as cystic fibrosis, sickle cell disease or thalassaemia.
• A scan has shown something that needs looking into further.
• You want earlier results than amniocentesis can give. Amniocentesis is a similar test that takes a sample of the fluid around the baby, but it is done a few weeks later.

Risk factors

• Getting older — the chance of chromosomal conditions rises with the pregnant person's age.
• A family history of a genetic condition.
• Being a known carrier of a genetic condition.
• A previous pregnancy affected by a chromosomal or genetic condition.
• Certain findings on an early ultrasound scan.

When to see a doctor

See a doctor urgently if:

• Heavy or increasing vaginal bleeding.
• A high temperature, shivering or chills.
• Fluid leaking from the vagina.
• Severe or worsening tummy or pelvic pain.
• Feeling very unwell, dizzy or faint.

Book a routine appointment if:

• You've been offered CVS and want to talk it through before deciding.
• You're unsure whether CVS or amniocentesis is the right choice for you.
• You want to know your own clinic's risk figures for miscarriage.
• You've had the test and your results haven't arrived when expected.
• You feel low, anxious or unable to cope while you wait.

Diagnosis

CVS is itself the test, so there's nothing to work out beforehand. Your doctor or midwife will talk with you about the benefits and risks, and you'll usually have time to ask questions and go away to think before you decide. You can normally take someone with you for support.

Tests that may be done

• An ultrasound scan first, to check how many weeks pregnant you are and where the placenta is.
• The sample itself: a thin needle through your tummy (transabdominal CVS), or a fine tube passed through your cervix (transcervical CVS). Your team will use whichever is safest for you.
• A rapid test that looks at a few specific chromosomes and gives results within a few days.
• A full chromosome analysis, which usually takes about two weeks.
• DNA testing for a specific inherited condition, if that is what's being checked — this can take longer.

What to expect at your appointment

You'll usually be in and out within about half an hour. You may be given a local anaesthetic to numb your tummy. Using the scan for guidance, the doctor guides a needle or fine tube to the placenta and draws off a tiny sample of tissue. It can feel strange or uncomfortable — a bit like a sharp period pain — for a short time. You'll be watched for a little while afterwards before you go home, and some clinics advise resting for the rest of the day.

Treatment

CVS isn't something you are treated for — it's a test. No treatment is needed afterwards, other than taking it easy for a day and watching for warning signs. The results may mean you are offered choices about your pregnancy: extra monitoring, planning the birth in a specialist unit, or — if a serious condition is found — the option to end the pregnancy. Those decisions are yours, and your team should support you either way.

Self-care at home

• Rest for the rest of the day, and avoid heavy lifting or strenuous exercise for a day or two.
• Ask your midwife or pharmacist what pain relief is safe to take in pregnancy before you take anything.
• Use a pad rather than a tampon for a few days, so you can see any bleeding clearly.
• Avoid sex for a few days if your clinic advises it.
• Keep your maternity unit's phone number somewhere easy to find.
• Eat and drink as normal — there's no special diet needed.

Medical treatments

No medical treatment is needed after CVS. If you have Rh-negative blood, you may be offered an injection to stop your body reacting to your baby's blood — your team will arrange this. If an infection is suspected, you'll be seen quickly and treated. If your results show a condition, your care team will explain what it means and talk through your options, which may include extra scans and monitoring, referral to a specialist or genetics team, and ongoing support.

When is surgery considered?

Surgery is not part of CVS.

Living with this condition

The hardest part is often the wait for results, which can feel very long. Try to keep your usual routines going where you can, lean on people you trust, and don't feel you have to keep the test or the results private if you'd rather not. Many people find it helps to have one or two people they can talk to openly.

Lifestyle tips

• Take it easy for a day or two, then get back to normal activity as you feel able.
• Keep your antenatal appointments, even if you feel anxious about them.
• Write down your questions as they come to you, so you don't forget them at appointments.
• Limit late-night online searching — it often makes anxiety worse. Ask your team instead.

Diet and exercise

There's nothing special you need to do. Eat and drink as normal, and go back to gentle exercise when you feel ready — usually within a day or two. Hold off on anything strenuous until any spotting has settled. Keep taking any pregnancy supplements your midwife has recommended.

Mental health and emotional wellbeing

It's completely normal to feel anxious, tearful or scared — waiting for results, and the decisions that may follow, can be very hard. Some people feel numb or detached; others feel overwhelmed. These are normal reactions, not a sign of weakness. If low mood or anxiety lasts or gets worse, please tell your midwife or doctor — support is available and you deserve it. If you ever feel you can't cope, or have thoughts of harming yourself, contact your local crisis line or your local emergency number straight away.

Prevention

CVS is a test, not an illness, so there's nothing to prevent. If you're deciding whether to have it, the useful question is whether the information would help you. Your midwife or doctor can talk this through with you without pushing you either way.

Screening programmes

Screening tests in pregnancy (blood tests and scans) are offered to everyone. They tell you the chance of certain conditions — they don't give a definite answer. If a screening result shows a higher chance, you'll be offered a diagnostic test such as CVS or amniocentesis. Screening is always your choice.

Complications

If left untreated

• CVS is a choice, not something that must be done. If you decide not to have it, nothing bad happens as a direct result — you simply won't have that early information. Other tests, such as the mid-pregnancy scan or amniocentesis later on, may still be offered.
• Miscarriage: a small risk, often quoted as around 1 in 100, though it may be lower. Ask your clinic for their own figures.
• An inconclusive result: occasionally the sample doesn't contain enough cells, and you may be offered a repeat test or amniocentesis.
• A small risk of infection, which is why fever or feeling unwell after the test needs checking the same day.
• Rarely, tests done very early (before 10 weeks) have been linked to problems with limb development — which is why CVS isn't done before then.
• CVS does not detect neural tube problems such as spina bifida — the mid-pregnancy scan checks for those.

Long-term outlook

For most people, CVS goes smoothly and gives clear answers. Whatever your results, you'll have a team around you to explain what they mean and help you plan the next steps. Many families find that clear information, even when it's hard news, helps them feel more in control. Support is available at every stage.

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