In the world of extensive innovative testing, prenatal exams to determine the development of the fetus are quite abundant.  Two of the most common methods to check the development are amniocentesis and CVS or formally called as chorionic villus sampling.  Both  tests are to determine the chromosomal developments of the fetus.  The amniocentesis works on extracting from the amnion or the amniotic sac fluids that will be checked and reviewed.  The CVS, meanwhile, works by gathering fluids from the chorionic villus or the placental tissue inside the womb.  The tests are conducted differently as well.  For one thing, the CVS can be conducted through two ways.  One would be through the cervix, and is known as the transcervical, and the other method is through the abdomen and is known as transabdominal.  The amniocentesis is only done through a transabdominal process.  The CVS procedure is both safe, although the cervix process has been noted to have some rates of miscarriage.

The process for both tests also differs from one another.  The CVS process requires that the patient be admitted in-patient at the hospital for at least 24 hours.  Both examinations require a full bladder to gather fully enough fluids from the concerned areas.  However, an additional step must be taken with the amniocentesis. This test is basically the blood type and the RH factor testing.  If the patient can  give results of Rh negative rating, then a medication called the Rhogam needs to be given to the patient.  The reasons why the tests are performed also vary.  For the amniocentesis, it is performed to detect chromosome problems such as anencephaly, Down syndrome, spin bifida and Rh incompatibility.  The CVS, on the other hand, is generally conducted to check the DNA, the chromosomes and the chemical markers of the fetus.

The time period of the tests also differs from one another.  The CVS can be conducted around 10 to 12 weeks after the last menstrual cycle of the woman.  Meanwhile, the amniocentesis is more perfect for being conducted around 16 to 20 weeks of the pregnancy.  When it comes to diagnosing some diseases, the CVS has also its limitations.   For one, it cannot determine neural tube defects like the spina bifida because the amniocentesis gets to test the fetus when it is already on a more advanced stage.  Lastly, the risks of taking CVS is slightly larger compared to the amniocentesis.  There have been cases wherein the mother encountered bleeding, infections, miscarriage and rupture of membranes.

Summary:
1. The CVS is known as tests that gather fluids from the placental tissue that is called the chorionic villus while the amniocentesis is gathered from the amniotic sacs.
2. The amniocentesis is only conducted through the abdomen while the CVS can be done through both ways, through the cervix and the abdomen.
3. The amniocentesis requires blood tests to check the Rh compatibility while the CVS does not.
4. The CVS can be done between ten to 12 weeks after the last menstrual cycle of the woman while the amniocentesis is conducted in the 16 to 20 weeks stage of pregnancy.