The key difference between amniocentesis and chorionic villus sampling is that in amniocentesis, a small amount of amniotic fluid is taken for testing while in chorionic villus sampling, a small sample of the placenta is taken for testing.
Amniocentesis and Chorionic Villus Sampling are two prenatal diagnostic procedures that determine certain fetal genetic abnormalities. These tests reveal the genetic defects during the pregnancy. When there is a higher risk for genetic defects, doctors will order the chorionic villus sampling while when there is relatively a low risk, they order to perform an amniocentesis. Both tests are safe but, chorionic villus test has a slightly higher risk of miscarriage than amniocentesis. Furthermore, chorionic villus test can be performed little earlier than amniocentesis. A pregnant woman may consider either chorionic villus sampling or amniocentesis during the occasions such as having a high risk screening test for Down syndrome, having an experience of genetic defects during the previous pregnancy, having one or more relatives affected with a genetic disorder, having a scan showing certain abnormal ultrasound features or to make sure her baby has genetic defects, etc.
CONTENTS
1. Overview and Key Difference
2. What is Amniocentesis
3. What is Chorionic Villus Sampling
4. Similarities Between Amniocentesis and Chorionic Villus Sampling
5. Side by Side Comparison – Amniocentesis vs Chorionic Villus Sampling in Tabular Form
6. Summary
What is Amniocentesis?
Amniocentesis is a prenatal diagnostic test that performs to determine chromosomal abnormalities in the fetus. When there is a relatively low risk of genetic defects, doctors may order to perform this test since it has a small risk for mother and the baby.
Figure 01: Amniocentesis
Therefore, through a fine needle inserted into the uterus through the abdomen, under ultrasound guidance, a sample from the amniotic fluid that surrounds the fetus in the uterus is extracted for this test. It is a quick test with a little discomfort. It can be performed after the 15 weeks of pregnancy. In contrast to chorionic villus sampling, this test has a low risk for both the mother and the baby. Therefore, using this test, doctors can identify certain genetic defects such as Down syndrome, chromosomal abnormalities.
What is Chorionic Villus Sampling?
Chorionic villus sampling is a prenatal diagnostic test performs at a higher risk of some genetic defects of the fetus. These risk factors can be conceiving at an age over 35, having a family history of problems, having unusual results after the first-trimester screening etc. Thus, this test is an alternative to amniocentesis but can be performed little earlier than it during the 10 to 13 weeks of pregnancy.
Figure 02: Chorionic Villus Sampling
The doctor takes a small sample from the placenta or the chorionic villus and performs a lab test to analyze the babies’ chromosomes. Sample extraction may be either through the cervix or through the abdomen. It produces more accurate results regarding the birth defects, Down syndrome, cystic fibrosis, sickle cell anaemia, Tay-Sachs disease, etc. Lab tests that use for chorionic villus sampling are karyotype tests, FISH tests and microarray analysis.
Though this test is a safe test, it has a slightly higher risk of miscarriage than amniocentesis. Furthermore, it can produce complications for your baby including transverse limb deficiencies, etc.
What are the Similarities Between Amniocentesis and Chorionic Villus Sampling?
- Amniocentesis and Chorionic Villus Sampling are two prenatal diagnostic tests.
- Both tests can diagnose genetic disorders.
- They are carried out during the pregnancy.
- Chorionic Villus Sampling is an alternative to amniocentesis.
- Both tests are relatively safe.
- These tests can determine the development of the fetus.
- Amniocentesis and Chorionic Villus Sampling check the chromosomal abnormalities.
- Both tests are informative for patient counselling and establishing widespread prenatal diagnostic and screening programs.
What is the Difference Between Amniocentesis and Chorionic Villus Sampling?
Prenatal diagnostic tests can detect the birth defects. Amniocentesis and chorionic villus sampling are two such methods that determine genetic defects of the fetus. Further, the amniocentesis can be performed after 15 weeks of pregnancy while chorionic villus sampling can be done at 10-13 weeks of pregnancy.
The below infographic presents more details on the difference between amniocentesis and chorionic villus sampling in tabular form.
Summary – Amniocentesis vs Chorionic Villus Sampling
Amniocentesis and chorionic villus sampling are two prenatal diagnostic tests that determine genetic defects in the fetus. A sample of amniotic fluid takes for the amniocentesis and performs a lab test to find out chromosomal abnormalities, fetal infections and sex determination, etc. On the other hand, a sample from the placenta is taken for the chorionic villus sampling. Amniocentesis can be performed in a transabdominal manner while chorionic villus sampling can be performed in both transcervical or transabdominal manner. The risk of miscarriage is slightly higher in chorionic villus sampling than amniocentesis. This is the difference between amniocentesis and chorionic villus sampling.
Reference:
1.“Chorionic Villus Sampling and Amniocentesis: Recommendations for Prenatal Counseling.”Centers for Disease Control and Prevention, Centers for Disease Control and Prevention. Available here
2.“Amniocentesis.” Wikipedia, Wikimedia Foundation, 22 Aug. 2018. Available here
Image Courtesy:
1.”Amniocentesis”By BruceBlaus – Own work, (CC BY-SA 4.0) via Commons Wikimedia
2.”Chorionic villi – high mag” By Nephron – Own work, (CC BY-SA 3.0) via Commons Wikimedia