What is amniocentesis?

http://www.babycenter.com/refcap/327.html

"Which birth defects can the test detect?
Amniocentesis can identify several hundred genetic disorders, including some of the most common:

• Nearly all chromosomal disorders, including Down syndrome and Edward's syndrome. The test is more than 99 percent accurate in diagnosing these conditions. An ultrasound, a combined first-trimester screening, or a multiple marker test may indicate whether your baby is likely to have these problems, but only amniocentesis can tell you for sure.

• Other genetic disorders such as cystic fibrosis, sickle cell disease, Tay-Sachs disease, and Huntington's disease. Neither the multiple marker test nor ultrasound will pick up these problems. Only amniocentesis can provide the information needed to diagnose them in the womb.

• Neural tube defects such as spina bifida and anencephaly.

More than 95 percent of the high-risk women who have amniocentesis receive good news from the results. Only about 5 percent will be found to have a baby with a problem. Amniocentesis doesn't detect every birth defect, however. A cleft lip or palate, for example, won't show up on the test."