Amniocentesis is surely one of the most important advances in prenatal diagnosis. During the procedure fluid from around the fetus is extracted by a fine needle. Doctors then examine the fluid for genetic defects, infections, or for fetal maturity, if indicated.
Amniocentesis is usually performed around sixteen weeks of pregnancy. The test can also be performed anytime after. There is a risk of approximately 1 in 200 women having a miscarriage after an amniocentesis. Therefore, the benefits for the procedure should outweigh the risks before proceding.
Your doctor should explain his or her reasons to have, or not to have, the procedure done. An "amnio" is usually recommended if the mother is 35 years or older at the expected due date. If the couple has had a previous child with chromosomal defects, or if they are carriers of a particular genetic disorder, then the test is also suggested.
Indications do vary and you should be sure to ask your physician to discuss amniocentesis with you at the beginning of your pregnancy.