Aminocentesis.

I heard some women talking about amniocentesis. Is this test for everyone?
No, not all pregnant women need amniocentesis. It is usually performed on women in the following circumstances:

women who will deliver after their 35th birthday
women who have had a previous baby with a birth defect
women who have a family history of birth defects
women who have a birth defect
women whose partners have a birth defect

When is the test done?
Amniocentesis is usually performed for prenatal evaluation between 16 and 20 weeks of pregnancy. Some doctors use amniocentesis at 11 or 12 weeks of pregnancy. However, risks are higher when it is done at this time; the test is still considered experimental when done this early.

How is amniocentesis performed?
Ultrasound is used to locate a pocket of fluid where the fetus and placenta are out of the way. Skin over the abdomen is cleaned and numbed with a local anesthetic. A long needle is then passed through the abdomen into the uterus, and fluid is withdrawn from the amniotic cavity with a syringe.

How much fluid is withdrawn?
About 1 ounce (30ml) of amniotic fluid is needed to perform tests.

What do they do with the amniotic fluid?
Fetal cells that float in the amniotic fluid can be grown in cultures. These cells are used to identify fetal abnormalities or to reassure you that your baby is healthy.

How many abnormalities can amniocentesis identify?
We know of more than 400 abnormalities a child can be born with. Amniocentesis can identify about 10% of them, or about 40 problems.

What kind of abnormalities can be found with amniocentesis?
The problems a physician can identify include the following:

chromosomal problems, particularly Down syndrome
skeletal diseases, such as osteogenesis imperfecta (fragility of the baby's bones)
fetal infections, such as herpes or rubella
central-nervous-system disease, such as anencephaly
blood diseases, such as erythroblastosis fetalis
chemical problems or deficiencies, such as cystinuria or maple-syrup-urine disease

Can't amniocentesis also determine the baby's sex?
Yes, but the test is not used for this purpose, except in cases in which the sex of the baby could predict a problem, such as hemophilia.

What are the risks of this test?
Risks are relatively low: Fetal loss from complications is estimated to be between 0.5 and 3%. Discuss it with your doctor before you have the test.

Who performs amniocentesis?
Only someone who has experience should perform the test, such as a physician at a medical center. Your doctor will be able to give you more information.

If I wouldn't end my pregnancy regardless of the baby's condition, why have amniocentesis?
If your doctor suggests it, you should seriously consider having the test. If a problem is detected, you and your family can prepare for it You can gather information about the problem. The test may also indicate the need for additional tests to determine if the fetus might have other problems. If any are found, you and your physician can take steps to ensure a smooth delivery and have any necessary procedures done as soon after the birth as possible. It is still a personal decision. Discuss it carefully with your doctor and your partner.