Use of Amniocentesis in Pregnancy
Amniocentesis is Used to Detect Birth Defects Early in Pregnancy
Oct 21, 2009
An amniocentesis is the most common prenatal test that a doctor may recommend to identify any birth defects or genetic problems. Fetal cells in the amniotic fluid can provide a wide range information on the genetic make-up of the fetus, including any abnormalities.
There is another prenatal test that can be performed earlier than an amniocentesis, which is called chorionic villus sampling (CVS). However, CVS does not identify as many abnormalities as an amniocentesis detects, such as neural tube defects.
How is an Amniocentesis Performed?
The mother's pregnant belly is first cleaned with an iodine solution. With the guidance of an ultrasound, a long, hollow needle is inserted into the uterus to extract some of the amniotic fluid. The mother and baby are closely monitored during and after the procedure to make sure neither one of them is under distress.
The sample of amniotic fluid is then taken to a lab to be analyzed for abnormalities. This should take approximately 24 to 35 days for results to come back.
This procedure is usually performed between weeks 16 and 18 of a pregnancy. It can sometimes be performed as early as the 14th week, and as late as the 20th week. Sometimes an amniocentesis is performed in late pregnancy to assess the development of the baby's lungs if necessary.
Who is an Amniocentesis Recommended For?
This prenatal test is generally recommended for women who:
- are over the age of 35 - about 80%-90% of amniocentesis procedures are performed solely because of the mother's age;
- already have a child with a chromosomal abnormality, such as Down Syndrome;
- already have a child with a neural tube defect, such as spina bifida;
- are carriers of an x-linked genetic disorder, such as hemophilia. The mother has about a 50-50 chance of passing this genetic disorder along;
- have conditions that may be passed on to the baby;
- previously had a an abnormal screening test. An amniocentesis will follow the first the test to determine if there is actually anything wrong with the baby.
Risks Associated With Amniocentesis
Side-effects of an amniocentesis may include cramping, vaginal bleeding or amniotic fluid leakage. There is a 1/1000 chance of developing an infection, and a 1/400 chance of a miscarriage as a result of an amniocentesis. For this reason, this procedure should only be performed if the benefits outweigh the risks.
For more pregnancy-related information, please visit: www.complete-pregnancy-guide.com
References:
1. Cherry, Sheldon H., Understanding Pregnancy & Childbirth, 1992
2. Eisenberg et al, What to Expect When You're Expecting, 1991
3. American Pregnancy Association
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