Chorionic Villus Sampling (CVS)

What Is Chorionic Villus Sampling (CVS)?

Chorionic villus sampling, or CVS in short, is a prenatal diagnostic test done between 11 and 13 weeks of pregnancy to determine if the baby has any chromosomal abnormalities, such as Down syndrome or other genetic disorders. CVS helps in making crucial decisions about pregnancy.

The doctor takes a small sample of cells from the small, finger-like projections on the placenta called chorionic villi. These cells go to the lab to check if the baby’s genes are healthy. The cells can be collected through the abdominal or the cervical canal.

Although chorionic villus sampling can provide important information about the baby's health, it is vital to understand its risks and be prepared for the results. Chorionic villus sampling may be used for chromosome and genetic testing in the first trimester of pregnancy. The CVS procedure is conducted earlier than other diagnostic tests, such as amniocentesis.

Chorionic villus sampling cannot detect certain birth defects, such as neural tube defects; instead, a genetic amniocentesis or ultrasound might be recommended.

The following are a few reasons that a woman may undergo chorionic villi sampling:

• A family history of a genetic disease, a previously affected child, chromosomal abnormalities, or a metabolic disorder.

• Maternal age over 35 years.

• Risk of a sex-linked genetic disease.

• Previous ultrasound with questionable or abnormal findings.

• Abnormal cell-free DNA test.

• If the mother is carrying multiple fetuses.

What Are the Types of CVS Procedures?

There are two types:

1) Cervical approach (transcervical):

• The vagina and cervix will be cleansed with an antiseptic solution. A speculum will be gently inserted so that the cervix can be seen.

• This approach does not require an anesthetic injection.

• With the help of ultrasound, a thin tube or catheter will be passed through the cervix to the chorionic villi.

• Using a tube, the cells will be gently suctioned into the catheter.

• The patient may experience a slight twinge or cramping.

• In some cases, more than one sample may be collected to obtain sufficient tissue for testing.

• The tube will then be gently removed.

2) Abdominal approach (transabdominal):

• The doctor will clean the abdomen with an antiseptic and numb the area with a local anesthetic. This may cause a brief stinging sensation.

• With ultrasound guidance, the doctor gently puts a tiny, thin needle through the abdomen into the uterus where the baby is. This can cause slight pain and cramps while the needle enters the uterus, and the cells will be suctioned into a syringe.

• In some cases, more than one sample may be collected to obtain sufficient tissue for testing.

• The needle will then be gently removed. A bandage will be placed over the site of the abdominal needle insertion.

• According to many sources, this is the most common method.

How to Prepare for CVS?

Before preparing for the procedure, the following steps are carried out:

• The doctor may ask if the patient is sensitive to or allergic to medications, latex, iodine, and anesthetic agents.

• The doctor may also ask about the patient's history of bleeding disorders or if they are taking any anticoagulants or other medications that could affect blood clotting. If so, the doctor may recommend discontinuing these medications before the procedure.

• The doctor might check if the mother’s blood is Rh-negative. Because during the test, the mother’s blood and the baby’s blood can sometimes mix. If this happens, Rh immunoglobulin is given.

• Usually, there is no particular diet restriction or activity before the chorionic villus sampling procedure.

• The patient may or may not be asked to have a full bladder right before the procedure, because it depends on the position of the placenta and uterus.

• Based on the medical condition, the doctor may request other specific preparation.

• You may also need to sign the consent form after discussing the risks with the doctor.

• Always bring a partner, a family member, or a friend for support.

What to Expect During the CVS Procedure?

Here’s what can be expected during the CVS procedure:

• The patient will be asked to lie down on an examination table with the abdomen exposed and place their hands behind their head.

• Vital signs, such as blood pressure, heart rate, and breathing rate, will be checked and followed by an ultrasound to check the fetal heart rate, gestational age, and the position of the placenta, fetus, and umbilical cord.

• The healthcare providers will apply a gel to the abdomen and then use a device known as an ultrasound transducer to show the baby's position on a monitor.

• Based on the placenta location, the procedure will be performed through the cervix or the abdominal wall.

• Local anesthesia is used to numb the area where the needle will be used (transabdominal approach).

• The procedure may take about 10 minutes. But the entire visit may take up to 30 minutes to an hour.

What Are the Risks and Benefits of CVS?

Some possible risks and complications caused by CVS may include:

• Infection.

• Miscarriage (small risk, about 1 in 100).

• Bleeding.

• Cramping.

• Leaking of amniotic fluid (water breaking).

• Preterm labor.

• Limb defects in infants, especially if CVS procedures are done before nine weeks (rarely).

• Rh sensitization (a type of immune response where the Rh-negative mother’s blood gets mixed with the Rh-positive blood of the fetus).

The benefits of CVS include:

• Early diagnosis: CVS is performed between 10 and 13 weeks of pregnancy, which is earlier than other diagnostic tests, such as amniocentesis. Early diagnosis can provide more time for parents to prepare for the birth of a child with a genetic or chromosomal abnormality and make informed decisions about their pregnancy.

• Accurate diagnosis: CVS is a highly accurate diagnostic test, with a reported accuracy rate of over 99 %.

• Reduced anxiety: Some women might feel scared if their baby could have a health problem. These tests can help them feel better by indicating whether the baby is healthy or if there’s something that requires extra care.

• Faster results: Results are usually available within a few days (much before amniocentesis).

• Opportunity for early treatment: In some cases, early diagnosis of a genetic or chromosomal abnormality may enable early treatment or intervention, thereby improving the baby's outcome.

What Is the Aftercare and Recovery Process for CVS?

After the procedure:

• Monitoring for both the patient and the baby will continue for a period.

• Slight cramping and light spotting might occur for a few hours or a day following this procedure.

• Immediately, lying down and resting for a few hours is recommended. Resting at home is also required.

• Strenuous activities and heavy lifting should be limited to a minimum of 48 hours.

• Douching or sexual activity should be avoided for two weeks or until directed by a healthcare provider.

• Avoid swimming, using a hot tub, or bathing till the spotting has completely stopped.

• The CVS tissue will be forwarded to a genetics lab for analysis.

• If you notice bleeding, water leaking from where the needle went in or from the vagina, or if you get a fever, chills, lots of bleeding, or bad tummy pain or cramps, tell your doctor right away!

• After a CVS procedure, it is recommended that you rest for at least one day.

How Do I Understand My CVS Results?

Your CVS reports may have different outcomes, like

• Normal (or negative): This means that no genetic or chromosomal conditions tested for were found in the sample.

• Abnormal (or positive): This indicates that a chromosomal or genetic condition has been detected.

• Unclear or ambiguous: This means the results are inconclusive. This may happen if the sample was too small or, in rare situations, due to a condition called placental mosaicism, where there is an abnormality in the placenta but not the fetus. In such cases, further testing may be recommended, such as amniocentesis.

Conclusion:

Chorionic villi sampling is a test that provides information about the fetus’s genetic and chromosomal condition. It has two approaches. Depending on the patient's condition, a suitable method will be selected. It is a simple test with minimal pain; the procedure is usually quick, and the results are faster than other tests.

Key Takeaways From iCliniq:

• Chorionic villi sampling is a prenatal genetic test done when the mother is about 11 to 13 weeks pregnant. It gives accurate and quick results.

• The procedure is quick and usually takes 10 to 20 minutes, depending on the type. It has a diagnostic accuracy of up to 99.6% and may have a 1-2% chance of unclear results.

• If you are planning to have a baby, have a family history of certain health problems, or are carrying more than one baby, your doctor may recommend a special test called a CVS test. And if you ever need help or have questions about this, you can always talk to our iCliniq obstetrician and gynecologist for guidance.