Amniocentesis Test
Amniotic Fluid Test (AFT) During Pregnancy

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amniocentesis diagnostic test

Amniocentesis Test

Contents

What Is It and Why Was I Recommended It?
How Is An Amniocentesis Performed?
How Safe Is The Test?
Does It Hurt?
How Much Does It Cost?
Are There Alternatives?


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Prenatal Care Information

What Is An Amniocentesis Test and Why Was I Recommended It?

If you receive an abnormal result from a routine prenatal blood test, or a quad scan (see prenatal tests), an amniocentesis screening will be recommended by your healthcare provider. Also known as an amniotic fluid test or AFT, an amniocentesis is usually performed between weeks 16 and 18 of pregnancy, but occasionally as early as weeks 13 or 14 or as late as weeks 23 and 24. The fetal cells, micro-organisms and chemicals in the amniotic fluid surrounding the fetus offer a wide range of information about your growing baby, such as genetic makeup and level of maturity. This fluid will help to clarify results from earlier tests, and offer a more concrete diagnosis on chromosomal abnormalities, fetal infections and possible birth defects. The most common diagnoses resulting from an amniocentesis test are Down syndrome (trisomy 21), Spina Bifida, Edwards syndrome (trisomy 18), Turner syndrome (monosomy X) and Fragile X. Amniocentesis can also be used for a paternity test while pregnant, although most people wait until after birth and use a paternity test kit.

Pregnant women are likely to be offered this test when then fall into one of the following categories:

• Results from a regular prenatal screening or quad screen test turn out to be abnormal, and evaluation of the amniotic fluid is necessary to check if there are any fetal abnormalities or potential pregnancy problems.

• The mother is having a pregnancy after 35, and the AFT is used primarily for Down syndrome testing. If the initial prenatal screening does not highlight an issue, then in consultation with her OB/GYN, a woman may choose to skip the amniocentesis.

• The mother already had a child with Down syndrome or with an enzyme deficiency such as cystic fibrosis. Genetic counselors may have recommended the test - see also Genetic testing during pregnancy.

• The mother is a carrier of an X-linked genetic disorder such as hemophilia which has a 50 percent chance of being passing onto any boy she has.

• If toxoplasmosis, cytomegalovirus, fifth disease or any other fetal infection is suspected.

• Both parents are carriers of an autosomal recessive inherited disorder such as sickle cell anemia or Tays-Sachs, which has a 1 in 4 chance of being passed to the baby.

How Is It Performed?

While lying on your back, your baby and placenta are located using an ultrasound scan. The location is important as your doctor will want to stay clear of both during the procedure. Your doctor may choose to numb your abdomen with an injection of local anesthetic, but because the injection can be as painful as the procedure itself, many practitioners chose to avoid it. They may rub a topic anesthetic to the area instead. Then, a long hollow needle (usually 3.5 inches long) is inserted through your abdominal wall, into your uterus and a small amount of amniotic fluid is drawn from the sac surrounding your fetus. Don't worry, the fluid will naturally replace itself and although there is a slight risk that the fetus may accidentally be pricked by the needle, this risk is reduced by the use of a pregnancy ultrasound scan for guiding. The entire procedure, including preparation time takes about 30 minutes. Amniocentesis is nearly 99 percent accurate in diagnosing or ruling out conditions such as Down syndrome. It generally takes about 2 weeks for results to come back, although some new techniques which are not yet widely available require only 48 hours.

How Safe Is The Test?

It is a very safe procedure. The risk of miscarriage is as low as 1 in 200 to 400 (1-2 percent). In comparison, the risk of miscarriage from a chorionic villus sampling test (CVS) is twice as high, although CVS may be carried out up to four weeks earlier, and may be preferable if risk of genetic defects is thought to be higher. You might experience some cramping side effects after an amniocentesis which can last from a few minutes to a few hours. Occasionally slight vaginal bleeding or amniotic fluid leakage may be experienced. This usually subsides after a few days of rest.

Does It Hurt?

Reports vary considerably on this question. Some women report the pain is no greater than an average injection while others claim the pain was considerable. If the woman has the test later in her pregnancy and experiences contractions, this can make it more difficult to insert the needle which will make it more painful. A topical anesthetic is rubbed to the site where the needle is inserted, so this can help numb the area.

How Much Does It Cost?

Some insurance plans cover the cost of an amniocentesis, particularly if the mother is over 35 years of age. You may need to provide your insurance company a referral from your healthcare provider. If you do not have coverage, estimates (vary from State to State) are between $1,200 to $2,000. See also: Prenatal care costs.

Are There Alternatives?

In 2011 a new simple blood test was introduced to the market called MaterniT21. This test can be carried out as early as week 10 of pregnancy and can predict with 99 percent certainty the presence of Down syndrome. As the test is rolled out to the greater market it is predicted that it will greatly reduce the amount of amniocentesis undertaken. The blood test is not without controversy however, as some argue that making it easier to test for Down syndrome will lead to more terminations. Studies show that as many as 90 percent of pregnancies which test positive for Down syndrome are terminated.

  Related Articles on Preparing For A Baby

For more about diagnostic tests during pregnancy, see the following:

Pregnancy Tips - Do's and don'ts for expecting moms.
Ultrasound Scan Photos and Video Images - Memento
Pregnancy Symptoms - Morning sickness, cramps, hemorrhoids.
Third trimester ultrasound scan: Why it is done, and what it shows.
Doula - Services of a Childbirth Assistant.

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