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Medical Video: Chorionic villus sampling offers couples peace of mind
Definition
What is choronic villus sampling?
Chorionic Villus Sampling (CVS) is a test carried out in early pregnancy to check if certain problems occur in the fetus. This is generally done when you or the father of the fetus have hereditary diseases in the family. This test can be done when you are pregnant at the age of 35 years - when you are over 35 years the risk of disability increases more. Genetic material in chorionic villus cells is the same as in baby cells. During CVS, chorionic villus cell samples are taken for examination. Chorionic villus cells are examined to find out the problem. This procedure is often carried out during the last 10th and 12th weeks.
The chorionic villus sample is taken using a flexible thin tube (catheter) which is inserted into the placenta. Samples can also be taken through long, thin needles that are inserted through the stomach into the placenta. Ultrasound is used to guide a catheter or needle to the right part to collect samples.
If your family has a history of certain diseases, CVS can be used to find genetic disorders. This test can also be used to determine the birth defects of chromosomes. CVS cannot be used to see the development and growth of a baby.
Chorionic villus sampling can be done early in pregnancy (at 10 to 12 weeks). This allows you to know the health of your baby and make a prior decision whether to continue or end the pregnancy. Results from CVS can be available faster than the results of amniocentesis.
When should I undergo choronic villus sampling?
CVS is not routinely recommended during pregnancy. This test is only used if the results of previous tests or your medical history state that your baby is at high risk of developing a genetic disorder. Some conditions that can be detected through CVS include:
- chromosome conditions, such as abnormalities that generally cause multiple levels of learning disabilities and various characteristics of physical features, or, abnormalities that can cause developmental disabilities
- genetic disorders, such as abnormalities that make thick and sticky body secretions, inhibit the function of certain organs
- disorders of the musculoskeletal system such as Duchenne, a genetic disorder that causes progressive muscle weakness and disability
- Blood disorders are like a condition that affects your body's ability to produce red blood cells, or, which affects how red blood cells carry oxygen throughout your body
- metabolic disorders such as antitrypsin deficiency, where your body cannot produce alpha-1 antitrypsin protein, or, where your body cannot produce the phenylalanine hydroxylase enzyme
- Mental health conditions such as fragile X syndrome, are conditions that can affect your appearance, intelligence and behavior
Like the conditions above, some other conditions that are less well known may also be detected by CVS. If there is a possibility that your fetus has a condition that can be detected by CVS, the specialist involved in the test will discuss it with you. You will be given risk-related advice from this procedure and information that can help you handle test results.
If the condition identified cannot be cured / treated, or if it causes severe disability in the baby, then the parent can decide to terminate. But if the parent decides to continue the pregnancy, CVS will provide early notification regarding the condition, so that it can provide time for both parents to prepare themselves for the challenges that will be faced in the future.
Prevention & warning
What should I know before undergoing choronic villus sampling?
CVS cannot detect neural tube defects. This is a birth defect that affects the brain and spinal cord. Normal results from chorionic villus sampling (CVS) do not guarantee that your baby will be healthy.
Amniocentesis (which is usually done at the end of pregnancy compared to CVS) can also be used to examine other diseases of the fetus, such as neural tube defects. If CVS does not show clear results, then amniocentesis may need to be done. Results from CVS can vary depending on the method of sampling.
If you have a vaginal infection, the stomach procedure will be used instead of the vaginal procedure. CVS causes bleeding that can cause mixing of your blood and your baby's. If you have Rh-negative blood, you will be given an Rh immunoglobulin vaccine (like RhoGAM) to prevent things that can harm your baby if he has Rh-positive blood.
Process
What should I do before undergoing choronic villus sampling?
A full bladder may be needed for chorionic villus sampling, so drink plenty of fluids before your CVS schedule. Depending on the position of the placenta, you may be asked to empty your bladder before the procedure. The doctor may ask you to sign the consent form before the procedure begins. Consider asking someone to accompany you on an examination day as emotional support or to take you home afterwards.
What is the choronic villus sampling process?
Chorionic villus sampling is usually performed by a perinatologist at a doctor's office or hospital. You do not need to stay overnight in a hospital unless a problem occurs during the procedure. There are two types of CVS that can be performed, transabdominal (through the stomach) chorionic villus sampling or transcervical (through the chorionic villus). The choice may depend on where the fetus and placenta are in the womb.
Through the stomach (transabdominal)
You will lie on your back on the examination table with your stomach naked. The gel will be applied to your stomach to be used with an ultrasound unit. An ultrasound (transducer) device that can give and capture sound waves will run on your stomach. Reflected sound waves will be sent to the computer to display photos of the uterus, fetus and placenta on the screen. Your doctor or ultrasound technician will look at the image to direct the needle used to collect chorionic villus samples. Your baby's heartbeat can also be checked during this procedure using ultrasound. For more detailed information, see the topic of Fetal Ultrasound.
The part of your skin that will be injected is cleaned with alcohol and anesthetized with medication. Your doctor then injects a long, thin needle through your abdomen and uterus into the placenta and collects chorionic villus cell samples.
After the sample is collected, your doctor will listen to your baby's heartbeat and check your blood pressure, pulse and breathing.
Through the cervix (transservary)
You will be asked to take off your clothes from the waist down and wrap the cloth around the waist. Then you will lie on your back on the examination table with your feet raised and assisted by a foot massage. This allows the doctor to see your genital area.
Your doctor will place a tool with a curved side (speculum) into your vagina. The speculum will carefully widen the vaginal wall separately, so that the inside of the vagina and cervix can be seen. The cervix will be cleansed with special soap.
Ultrasound will be used to help the doctor direct the catheter through your cervix to the placenta. An ultrasound (transducer) device that delivers and captures sound waves that will run on your stomach. Reflected sound waves are sent to the computer to display images of the uterus, your baby, and the placenta on the screen. Your baby's heartbeat can also be checked during the procedure using ultrasound. When the catheter is placed correctly, a sample of chorionic villus cells will be collected.
After the sample is collected, your doctor can listen to your baby's heartbeat and check your blood pressure, pulse and breathing.
What should I do after undergoing choronic villus sampling?
After the tissue sample is removed, the doctor will use ultrasound to monitor the baby's heartbeat. You may experience slight vaginal bleeding after the procedure. Tissue samples will be analyzed in the laboratory. Results can be taken several days or several weeks, depending on the complexity of laboratory analysis.
If you have questions relating to the process of this test, consult your doctor for a better understanding.
Explanation of Test Results
What do the test results mean?
Cells from your baby are carefully looked at by checking whether the number and arrangement of genetic material (chromosomes) is right and showing genetic disease. There are usually 46 chromosomes in each cell, arranged in 23 pairs. Chromosomes can also tell the sex of your baby. It takes 1 to 2 weeks before the CVS results come out.
Normal:
There are no abnormalities found in genetic material from chorionic villus cells.
Abnormal:
The finding of abnormalities in genetic material from chorionic villus cells.
Hello Health Group does not provide medical advice, diagnosis or treatment.
