At which point during pregnancy can chorionic villus sampling first be performed quizlet?

Chorionic villus sampling (CVS) is a test you may be offered during pregnancy to check if your baby has a genetic or chromosomal condition, such as Down's syndrome, Edwards' syndrome or Patau's syndrome.

It involves removing and testing a small sample of cells from the placenta, the organ linking the mother's blood supply with the unborn baby's.

When CVS is offered

CVS is not routinely offered in pregnancy.

It's only offered if there's a high chance your baby could have a genetic or chromosomal condition.

This could be because:

an antenatal screening test has suggested your baby may be born with a condition, such as Down's syndrome, Edwards' syndrome or Patau's syndrome
you had a previous pregnancy affected by a genetic condition
you have a family history of a genetic condition, such as sickle cell disease, thalassaemia, cystic fibrosis or muscular dystrophy

It's important to remember that you do not have to have CVS if it's offered. It's up to you to decide whether you want it.

A midwife or doctor will speak to you about what the test involves, and let you know what the possible benefits are, to help you make a decision.

Find out more about why CVS is offered and deciding whether to have it

How CVS is performed

CVS is usually carried out between the 11th and 14th weeks of pregnancy, although it's sometimes performed later than this if necessary.

During the test, a small sample of cells is removed from the placenta using 1 of 2 methods:

transabdominal CVS – a needle is inserted through your tummy (this is the most common method used)
transcervical CVS – a tube or small forceps (smooth metal instruments that look like tongs) are inserted through the cervix (the neck of the womb)

The test itself takes about 10 minutes, although the whole consultation may take about 30 minutes.

The CVS procedure is usually described as being uncomfortable rather than painful, although you may experience some cramps that are similar to period pains for a few hours afterwards.

Find out more about what happens during CVS

Getting your results

The first results of the test should be available within 3 working days and this will tell you if Down's syndrome, Edwards' syndrome or Patau's syndrome has been discovered.

If rarer conditions are also being tested for, it can take 2 to 3 weeks or more for the results to come back.

A specialist doctor (obstetrician) or midwife will explain what the screening results mean and talk to you about your options.

There's no cure for most of the conditions found by CVS, so you'll need to consider your options carefully.

You may decide to continue with your pregnancy while gathering information about the condition so you're fully prepared.

Find out more about having a baby that might be born with a genetic condition

Or you may consider ending your pregnancy (having a termination).

Find out more about the results of CVS

Miscarriage and infections.

Before you decide to have CVS, the possible complications will be discussed with you.

CVS can cause miscarriage, the loss of the pregnancy in the first 23 weeks.

The chance of miscarrying after CVS is up to 1 in 100.

You might also get an infection, or need to have CVS again because it was not successful the first time.

Read more about the complications of CVS

What are the alternatives?

An alternative to CVS is a test called amniocentesis.

This is where a small sample of amniotic fluid, the fluid that surrounds the baby in the womb, is removed for testing.

It's usually carried out between the 15th and 18th week of pregnancy, although it can be performed later than this if necessary.

This test can also cause a miscarriage, but your pregnancy will be at a more advanced stage before you can get the results, so you'll have less time to consider your options.

If you're offered tests to look for a genetic or chromosomal condition in your baby, a specialist involved in carrying out the test will be able to discuss the different options with you and help you make a decision.

Page last reviewed: 20 July 2018
Next review due: 20 July 2021

What is a karyotype test?

A karyotype test looks at the size, shape, and number of your chromosomes. Chromosomes are the parts of your cells that contain your genes. Genes are parts of DNA passed down from your mother and father. They carry information that determines your unique traits, such as height and eye color.

People normally have 46 chromosomes, divided into 23 pairs, in each cell. One of each pair of chromosomes comes from your mother, and the other pair comes from your father.

If you have more or fewer chromosomes than 46, or if there is anything unusual about the size or shape of your chromosomes, it can mean you have a genetic disease. A karyotype test is often used to help find genetic defects in a developing baby.

Other names: genetic testing, chromosome testing, chromosome studies, cytogenetic analysis

What is it used for?

A karyotype test may be used to:

Check an unborn baby for genetic disorders
Diagnose a genetic disease in a baby or young child
Find out if a chromosomal defect is preventing a woman from getting pregnant or is causing miscarriages
Check a stillborn baby (a baby that died late in pregnancy or during birth) to see if a chromosomal defect was the cause of death
See if you have a genetic disorder that could be passed along to your children
Diagnose or make a treatment plan for certain types of cancer and blood disorders

Why do I need a karyotype test?

If you are pregnant, you may want to get a karyotype test for your unborn baby if you have certain risk factors. These include:

Your age. The overall risk of genetic birth defects is small, but the risk is higher for women who have babies at age 35 or older.
Family history. Your risk is increased if you, your partner, and/or another one of your children has a genetic disorder.

Your baby or young child may need a test if he or she has signs of a genetic disorder. There are many types of genetic disorders, each with different symptoms. You and your health care provider can talk about whether testing is recommended.

If you are a woman, you may need a karyotype test if you've had trouble getting pregnant or have had several miscarriages. While one miscarriage is not uncommon, if you have had several, it may be due to a chromosomal problem.

You may also need a karyotype test if you have symptoms of or have been diagnosed with leukemia, lymphoma, or myeloma, or a certain type of anemia. These disorders can cause chromosomal changes. Finding these changes can help your provider diagnose, monitor, and/or treat the disease.

What happens during a karyotype test?

For a karyotype test, your provider will need to take a sample of your cells. The most common ways to get a sample include:

A blood test. For this test, a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
Prenatal testing with amniocentesis or chorionic villus sampling (CVS). Chorionic villi are tiny growths found in the placenta.

For amniocentesis:

You'll lie on your back on an exam table.
Your provider will move an ultrasound device over your abdomen. Ultrasound uses sound waves to check the position of your uterus, placenta, and baby.
Your provider will insert a thin needle into your abdomen and withdraw a small amount of amniotic fluid.

Amniocentesis is usually done between week 15 and 20 of pregnancy.

For CVS:

You'll lie on your back on an exam table.
Your provider will move an ultrasound device over your abdomen to check the position of your uterus, placenta, and baby.
Your provider will collect cells from the placenta in one of two ways: either through your cervix with a thin tube called a catheter, or with a thin needle through your abdomen.

CVS is usually done between week 10 and 13 of pregnancy.

Bone Marrow Aspiration and Biopsy. If you are being tested for or treated for a certain type of cancer or blood disorder, your provider may need to take a sample of your bone marrow. For this test:

You'll lie on your side or your stomach, depending on which bone will be used for testing. Most bone marrow tests are taken from the hip bone.
The site will be cleaned with an antiseptic.
You will get an injection of a numbing solution.
Once the area is numb, the health care provider will take the sample.
For a bone marrow aspiration, which is usually performed first, the health care provider will insert a needle through the bone and pull out bone marrow fluid and cells. You may feel a sharp but brief pain when the needle is inserted.
For a bone marrow biopsy, the health care provider will use a special tool that twists into the bone to take out a sample of bone marrow tissue. You may feel some pressure on the site while the sample is being taken.

Will I need to do anything to prepare for the test?

You don't need any special preparation for karyotype testing.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

Amniocentesis and CVS tests are usually very safe procedures, but they do have a slight risk of causing a miscarriage. Talk to your health care provider about the risks and benefits of these tests.

After a bone marrow aspiration and biopsy test, you may feel stiff or sore at the injection site. This usually goes away in a few days. Your health care provider may recommend or prescribe a pain reliever to help.

What do the results mean?

If your results were abnormal (not normal,) it means you or your child has more or fewer than 46 chromosomes, or there is something abnormal about the size, shape, or structure of one or more of your chromosomes. Abnormal chromosomes can cause a variety of health problems. The symptoms and severity depend on which chromosomes have been affected.

Some disorders caused by chromosomal defects include:

Down syndrome, a disorder that causes intellectual disabilities and developmental delays
Edwards syndrome, a disorder that causes severe problems in the heart, lungs, and kidneys
Turner syndrome, a disorder in girls that affects the development of female characteristics

If you were tested because you have a certain type of cancer or blood disorder, your results can show whether or not your condition is caused by a chromosomal defect. These results can help your health care provider make the best treatment plan for you.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about a karyotype test?

If you are thinking about getting tested or have received abnormal results on your karyotype test, it may help to speak to a genetic counselor. A genetic counselor is a specially trained professional in genetics and genetic testing. He or she can explain what your results mean, direct you to support services, and help you make informed decisions about your health or the health of your child.

References

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How early in a pregnancy can CVS be performed quizlet?

The chorionic villi are wispy projections of placental tissue that share the baby's genetic makeup. The test can be done as early as 10 weeks of pregnancy.

At what gestational age can chorionic villus sampling?

Typically, CVS is done at 10-12 weeks' gestation, and amniocentesis is done at 15-18 weeks' gestation.

Can CVS be done after 13 weeks?

CVS is usually done between the 10th and 12th weeks of pregnancy. Unlike amniocentesis (another type of prenatal test), CVS does not provide information on neural tube defects, such as spina bifida.

When might a pregnant woman consider having CVS quizlet?

Chorionic villus sampling, or CVS testing, is done during pregnancy to find out if your baby has certain genetic problems. You do not have to get CVS testing. If you choose to do so, you'll undergo it when you're around 10 to 13 weeks pregnant. The test is safe, causes minimal discomfort and is very accurate.

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