Chorionic Villus Sampling (CVS)

WHAT IS CHORIONIC VILLUS SAMPLING?

Chorionic villus sampling (CVS) is a test performed during the prenatal stage of a pregnancy in which a sample is taken from the placenta. The samples consisting of cells called the chorionic villi are taken from the abdominal wall or the cervix region attached to the walls of the uterus. 

The chorionic villi are little parts in the placenta which is formed from the egg which has been fertilized as they have the same genes as the baby. They have flexible strand structural projection in the placental tissue and they have the same genetic make-up as the child.

It can also be used for the detection of birth defects, diseases acquainted with the gene, or other problems that may be encountered during pregnancy. Chromosomal problems like Down’s syndrome, cystic fibrosis, sickle cell anemia, or Tay-Sachs disease.  The placenta is said to provide nutrients and oxygen to the unborn baby and extract waste products from the unborn baby’s blood. 

The chorionic villus sampling test is done as early as 10 weeks into the pregnancy and the CVS is recommended in the case of risk factors involved for early detection as it is said to have an accuracy of over 98% while diagnosing for chromosomal defects. 

One of the chorionic villus sampling advantages is that it can also detect the sex of the unborn baby.

WHEN IS CHORIONIC VILLUS SAMPLING DONE?

Chorionic villus sampling can give information about the unborn baby’s gene and it is proffered when solutions are needed based on the management of the pregnancy or necessity to go on with the pregnancy. Other tests can be used also like amniocentesis.

When a prenatal test is conducted and the result is positive especially during the first trimester the chorionic villus sampling may be recommended to deduct a diagnosis. 

The CVS can be done due to the following:

1. History of a chromosomal condition in a previous pregnancy.
2. A previous case of Down syndrome ky.
3. Age range as women within the age of 35 years and older have high risks of the chromosomal condition.
4. A previous case of a specific genetic condition or carrier of a genetic condition.
5. Diagnosis of a condition like Cystic fibrosis.
6. Identifying a genetic condition known as the Tay-Sachs disorder.

The chorionic villus sampling is limited as it cab does not detect some basic birth defects like the neural tube defects whereby if the defect is somehow noticeable, ultrasound or genetic amniocentesis will be recommended instead.

ELIGIBILITY FOR CHORIONIC VILLUS SAMPLING

Some women are restricted from undergoing the transcervical chorionic villus sampling for reasons such as:

1. Bleeding or spotting through the vagina in the previous weeks.
2. Acute infection in the cervix region of the vagina such as herpes.
3. Placenta with little or no access due to the projection in the lower part of the uterus or a noncancerous growth in the cervix region.

Women other than the ones stated above are allowed to undergo the CVS test.

CHORIONIC VILLUS SAMPLING PROCEDURE

Chorionic villus sampling is categorized into the procedure before, during, and after the test is done. These are explained briefly below:

1. Before the Procedure,

One of the recommendations before the procedure is that the patient may need to have a full bladder before undergoing the CVS. Therefore, the amount of fluid to be taken into the system by the patient will be related as well as other tests to be taken just before the test.

Also, the doctor is to explain the process, possible complications, and risks involved before a consent form is signed.

• During the Procedure,

The test is done in the doctor’s office where the doctor will utilize ultrasound to determine the position of the placenta and the gestational age of the baby. 

The patient will lay down on the examination table with the abdomen wide exposed then a gel will be applied to the abdomen after which a small device called the ultrasound transducer is used to indicate the position of the baby which is clearly shown on the monitor.

Afterward, the ultrasound image is used as a guide to extract the samples from the placenta through the abdominal wall or cervix.

For the transabdominal chorionic villus sampling, the abdomen is cleansed with an antiseptic before the chorionic villus sampling needle which is long and thin is inserted through the abdominal walls to the uterus where a sting is felt and possible cramp when the needle enters the uterus. Then, the sample is extracted from the placenta where the tissue will be withdrawn through the syringe and the needle will be removed.

For the second case which is the transcervical chorionic villus sampling, the vagina will be properly cleansed with antiseptic alongside the cervix which will then be opened with a speculum, and a thin, hollow tube bill be inserted through the cervix until the catheter gets to the placenta and a soft suction will be made before finally extracting the small tissue to be used aa a sample.

• After the Procedure,

A little vaginal bleeding might occur after the procedure but the patient can return to usual activities of the day, though overstressing should be avoided alongside any sexual activity for at least a day. The results might take few days or a week all depending on the complexity of the laboratory analysis.

CHORIONIC VILLUS SAMPLING RESULT

Most times the chorionic villus sampling might not clearly show diagnosis so amniocentesis is used to clarify the diagnosis.

Indications of a genetic or chromosomal disorder by the chorionic villus sampling not being treatable might lead to termination of the baby or not depending on counseling given by the doctor.

CHORIONIC VILLUS SAMPLING RISKS

Risks of chorionic villus sampling involve heavy bleeding, uterine contractions, fever, and fluid leaking from the vagina. 

Other chorionic villus sampling disadvantages involved are:

• Miscarriage

During the process of chorionic villus sampling, a miscarriage can occur though the possibility of occurrence is placed at 0.22%.

• Rh Sensitization

Due to the procedure, the baby’s blood cells might migrate into the patient’s bloodstream, though, if the Rh blood indicates negative and no antibodies are present for Rh-positive, the Rh immune globulin will be administered to the patient immediately after the chorionic villus sampling. 

Therefore, halting the production of Rh antibodies and preventing them from crossing the placenta of the patient, and damaging the red blood cells of the baby.

• Infection

This rarely occurs through the CVS test may ignite an infection.

CHORIONIC VILLUS SAMPLING COST

The cost of a chorionic villus sampling test varies depending on the country, hospital, etc. In the U.S, chorionic villus sampling price ranges from $1300 to $4800 US Dollars.

FAQs

• Is CVS safer than amniocentesis?

The safety of the procedure is dependent on the timeline for the pregnancy, the amniocentesis is safe when the pregnancy is in the second trimester, also the same case applies for the transcervical CVS while the transabdominal is done before the first 15 weeks of the pregnancy.

• Is a CVS test painful?

Chorionic villus sampling is accompanied by just a stinging sensation, though for some cases, local anesthesia is administered to the patient to numb the area in which the needle will be injected.

• Can chorionic villus sampling tell the gender?

The chorionic villus sampling can be used to determine the sex of a baby as the female fetus tends to have a wild-type genotype, though further analysis for the guy is recommended.

• Is chorionic villus sampling accurate?

Chorionic villus sampling is said to have an accuracy of about 98% relative to the diagnosis of chromosomal defects.

• Which prenatal diagnostic method is safest?

Ultrasonography and blood tests are identified to be the safest diagnostic method, though it is mostly done to determine the need for further tests like chorionic villus sampling and amniocentesis.