Chorionic Villus Sampling (CVS) is a procedure in which a sample of tissue is collected from the placenta for laboratory analysis.

Placental tissue contains the same genetic material as the fetus, so it can be used to detect fetal chromosomal abnormalities and certain genetic disorders.

Examples of abnormalities that can be detected include:

• Abnormalities in the number of chromosomes (Aneuploidy) such as:
  • Downsyndrome
  • Single-gene abnormality such as Thalassemia disease
  • Structural chromosomal abnormalities, such as the presence of extra or missing segments in certain parts of a chromosome
  • Genetic disorders that are inherited within a family

CVS is a diagnostic test, which differs from screening tests such as NIPT that are used only to assess risk.
 

CVS can be used to diagnose various genetic abnormalities, such as:

1. Abnormal number of chromosomes, such as Down syndrome (Trisomy 21, Trisomy 18, Trisomy 13)
2. Inherited genetic disorders, such as Thalassemia disease
3. Structural chromosomal abnormalities
4. Certain genetic conditions that can be detected using Chromosome Microarray Analysis (CMA), a high-resolution molecular genetic testing technique

CVS cannot detect all genetic abnormalities. Doctors will determine the suitability of the test based on each patient’s individual factors.
 

There are several methods for diagnosing fetal abnormalities. Two commonly used procedures are Chorionic Villus Sampling (CVS) and amniocentesis, which differ in several aspects as follows:
 

Topic	Chorionic Villus Sampling (CVS)	Amniocentesis
Gestational age	About 10-13 weeks of gestation	About 15-20 weeks of gestation
Sample collected	Placental tissue	Amniotic fluid
Purpose	Diagnose genetic abnormalities	Diagnose genetic abnormalities
Time to get results	Depends on the type of test performed	Depends on the type of text performed

Doctors will determine the most appropriate test based on gestational age, risk level, and each patient’s individual factors.
 

CVS offers several advantages, including:

• It can be conducted as early as around 10–13 weeks of pregnancy
• It helps diagnose genetic abnormalities at an early stage of pregnancy
• If an abnormality is detected, the mother and family can consult with doctors to plan appropriate prenatal care early on
• It has high accuracy in diagnosing chromosomal abnormalities, generally around 98–99%

However, doctors will determine the suitability of the test on an individual basis for each patient.

Doctors may recommend CVS in the following cases:

• Mothers who have screening results, such as NIPT or other tests, indicating a high risk of genetic disorders occurring
• Couples who are carriers of genetic disorders, such as thalassemia trait.
• A history of having a child with genetic or chromosomal abnormalities
• A family history of certain genetic disorders

Doctors will assess the results to determine whether each patient is suitable for CVS before making any decisions.
 

Before undergoing CVS, doctors will carefully assess the health of both the mother and the fetus to ensure that the procedure is appropriate and as safe as possible.

In some cases, doctors may recommend certain preparations prior to the procedure, such as an ultrasound to evaluate the position of the placenta, gestational age, and the condition of the fetus. They will also review the mother’s medical history, including underlying conditions, medications, and previous pregnancies.

Providing complete and accurate health information to the doctor helps the medical team plan the procedure appropriately and reduce potential risks during the procedure.
 

The CVS procedure generally involves the following steps:

1. Ultrasound examination
    The doctor performs an ultrasound to determine the position of the fetus, placenta, and amniotic sac.
2. Local anesthesia
   A local anesthetic is administered to numb the skin.
3. Collection of placental tissue sample
   The doctor may use one of the following methods to collect the sample:
   • Using a thin needle inserted through the abdominal wall into the placenta
   • Using a small instrument inserted through the cervix to collect the tissue sample
4. Laboratory analysis
   The tissue sample is sent for genetic analysis in the laboratory.

The entire procedure typically takes about 15–20 minutes, and patients can usually go home afterward.

 

Although CVS is a widely used procedure, it may carry some risks, including:

• Light vaginal bleeding or leakage of amniotic fluid, which occurs in about 1% of cases
• Mild abdominal pain after the procedure
• A risk of miscarriage, occurring in approximately 2–3% of cases

Doctors will explain the risks and benefits of the procedure before deciding whether to proceed.

 

After undergoing Chorionic Villus Sampling (CVS), patients can usually return home on the same day. However, during the first 1–2 days after the procedure, it is important to prioritize rest and closely monitor any symptoms to allow the body to recover properly.

Doctors typically recommend avoiding strenuous activities for about one week, such as heavy lifting, sexual intercourse, vigorous exercise, or any activity that may increase pressure on the abdomen. Less strenuous daily activities can be carried out as usual if there are no abnormal symptoms.

Some patients may experience mild symptoms after the procedure, such as a feeling of heaviness or discomfort in the lower abdomen. These symptoms are common and usually resolve on their own within a short time. Pain relief medication may also be taken on the first day if needed.

Patients should contact their doctor or seek medical attention immediately if any of the following symptoms occur:

• Severe or persistent abdominal pain
• Vaginal bleeding
• Fever or chills
• Unusual fluid leakage from the vagina

Following the doctor’s instructions carefully and attending scheduled follow-up appointments will help ensure safe prenatal care after the procedure.
 

• Q: Is CVS painful?
  A: You may experience some discomfort, but a local anesthetic is given before the procedure to help reduce pain.
• Q: Is CVS safe?
  A: There are small risks, such as leakage of amniotic fluid (about 1%) and a risk of miscarriage (approximately 2–3%).
• Q: How long does the CVS procedure take?
  A: The entire procedure takes about 20 minutes.
• Q: Is recovery needed after CVS?
  A: Patients can usually return home on the same day. However, during the first 1–2 days after the procedure, it is important to rest and closely monitor any symptoms to allow proper recovery.
• Q: What conditions can CVS detect?
  A:
  • Abnormalities in the number of chromosomes, such as Down syndrome (Trisomy 21, Trisomy 18, Trisomy 13)
  • Inherited genetic disorders, such as Thalassemia disease
  • Structural chromosomal abnormalities
  • Certain genetic conditions detectable by Chromosome Microarray Analysis (CMA), a high-resolution molecular genetic testing technique
• Q: How long does it take to get CVS results?
  A: The turnaround time depends on the type of test. For example, standard chromosomal analysis takes about 2–3 weeks, Chromosome Microarray Analysis (CMA) takes about 5–7 days, and Rapid Aneuploidy Testing takes about 3–5 days.
• Q: At what stage of pregnancy can CVS be performed?
  A: CVS can be performed between 10–13 weeks of pregnancy.

Chorionic Villus Sampling (CVS) at Bumrungrad Hospital

Bumrungrad Hospital provides prenatal diagnostic services by a team of specialists in Maternal-Fetal Medicine, supported by standardized genetic testing technologies.
Treatment is tailored to each individual patient. Doctors provide guidance on diagnostic options, associated risks, and appropriate prenatal care plans based on each patient’s specific needs.