Chorionic villus sampling or CVS is a prenatal test, one done during pregnancy, to diagnose any type of chromosomal abnormality in a fetus or an unborn baby. Genetic disorders and conditions like Down syndrome can be detected with the help of this test. There is another test, which is usually considered a substitute, called amniocentesis test. CVS or chorionic villus sampling test is more common.
Procedure of Chorionic Villus Sampling Test
Chorionic villi, which are cells in the fingerlike projections of the placenta, are obtained from pregnant woman. The chorionic villi are studied and extensive genetic analysis is conducted to understand any existing and even preempt any possible chromosomal abnormality or genetic disorder. The CVS test is usually carried out when there is a risk or chance of genetic disorders. Families that have genetic ailments and in case firstborns have had chromosomal abnormalities or birth defects would call for a CVS test. Otherwise, it would be advised only if there is some sign of such anomalies in the fetus or depending on the prevailing health and genetics of the mother. CVS is not an imperative procedure. It is not common either. The procedure is in fact avoided because it is invasive. It is also deemed risky because there is a minor risk of miscarriage.
CVS test is carried out in the tenth week or till the thirteenth week of pregnancy. The test should not be carried out before the tenth week and it should never be carried out after thirteen weeks. In contrast, amniocentesis test is carried out in the sixteenth week. It can be conducted anytime between the fifteenth and twentieth week, no sooner and no later. Amniocentesis test is hence classified as the less desirable test since it is carried out at a more advanced stage of pregnancy. CVS test is neither done too soon in the pregnancy nor too late.
List of Pros of Chorionic Villus Sampling Test
1. Detecting Genetic Defects and Chromosomal Anomalies
CVS can detect almost every chromosomal abnormality known to man. It can detect Down syndrome, Turner syndrome and other sex chromosome anomalies, trisomy 13 and trisomy 18 among others. Hundreds of genetic defects can also be identified using CVS. The test can detect Tay-Sachs disease, sickle cell disease and cystic fibrosis.
2. Complementing Other Tests
CVS test can be used in conjunction with ultrasound and blood tests to identify other disorders, notably neural defects. The other tests are relatively noninvasive and painless. Both parents can be subjected to the additional tests, especially blood test, so the collective testing can facilitate better and more inclusive testing. Genetic analyses of the mother and the father can be used while studying the findings of the CVS test for more accurate diagnoses.
3. Accurate Analyses
Compared to amniocentesis test, chorionic villus sampling is less painful. It is an uncomfortable test as reported by pregnant women but it is not painful as is the case with amniocentesis test. The test findings can be accurate or there can be some uncertainty. However, genetic analyses and medical histories of the parents, associated tests such as blood tests and ultrasound tests can be used for accurate diagnoses of existing or preexisting and possible chromosomal anomalies and genetic defects in the fetus.
List of Cons of Chorionic Villus Sampling Test
1. Limited Application
The chorionic villus sampling test is not recommended to any pregnant woman unless there is a substantial risk of a newborn having genetic defects or chromosomal anomalies. This can only happen if there are genetic disorders in the family of the mother or the father, either or both parents. Alternatively, there should be some signs that the fetus is not developing normally and there is undisputed evidence that the newborn may have some preexisting condition or birth defect.
2. Invasive & Uncomfortable
The extraction of the cells is a painful procedure. A tube or a needle has to be inserted into the cervix of the pregnant woman to reach the placenta wherefrom the cells or chorionic villi must be extracted. The insertion of the tube or needle is invasive. It is uncomfortable and can be painful if there is even the slightest of error.
3. Side Effects
Cramps are common side effects of the invasive procedure. The insertion will always have some physical discomfort and it could be severe in some cases. The cramps can be just as severe as menstrual cramps and they can be quite unnerving during pregnancy.
The side effects may still be endured by a pregnant woman, especially knowing or in the hope that the baby doesn’t have any genetic or chromosomal abnormality. However, there is a small chance of miscarriage. It is also possible that the test itself will cause some damage to the fetus, which otherwise may not have any chromosomal or genetic anomaly. The risks are the reason why CVS is not a common test.