Amniocentesis is a diagnostic procedure that involves withdrawing a small amount of fluid from the sac surrounding the fetus. A long, thin needle is inserted through the abdomen and into the uterus, and a small amount of fluid is taken from the sac. Before the procedure, the exact location of the fetus is determined by ultrasound.
Amniocentesis can be used to diagnose a large number of genetic and chromosomal abnormalities in the fetus. It is also helpful for diagnosing the severity of Rh incompatibility, lung maturity, and neural tube defects (such as spina bifida).
Amniocentesis is a procedure done during pregnancy to test a fetus for certain kinds of birth defects. It involves the withdrawal of a small amount of amniotic fluid (the fluid surrounding a developing fetus) from the uterus. This procedure is typically performed after 15 weeks gestation.
People with specific risks for chromosome abnormalities, inherited genetic diseases, open neural tube defects or other conditions for which tests are available should consider amniocentesis.
The test most commonly performed on amniotic fluid is a chromosome analysis, a test for disorders such as Down syndrome. Testing for individual genetic disorders such as cystic fibrosis, Tay-Sachs disease and sickle cell disease can be done on the same sample when indicated. Amniotic fluid can also be tested for the alpha fetoprotein level. This level helps determine the likelihood for open neural tube defects, such as spina bifida and anencephaly. Even identity testing to determine who the father is can be performed from an amniocentesis sample.
Every pregnancy has a risk — usually 3 percent to 5 percent — for birth defects that do not have a known cause. A few examples are cleft lip, non-specific mental retardation and most heart defects. Amniocentesis is not able to test for these types of conditions. Furthermore, tests for single-gene disorders are not typically done unless it is known there is a significant risk to the fetus at the time of the amniocentesis procedure.
You should read all the material we send you, including this brochure, the consent form and the precautions that we ask you to follow after the test. Please write down any questions you have for us and bring them with you to the clinic.
Your physician will explain the amniocentesis procedure and its risks. You will be then asked to sign the informed consent form. You may decide not to have the procedure up to the time that we perform it.
Before the procedure, the doctor will perform an ultrasound scan (sonogram) which shows a picture of the uterus, the placenta, the amniotic fluid and the fetus on a screen. After reviewing the image, the doctor will insert a very thin needle through the woman’s abdomen into the uterus and draw out about 1 ounce of amniotic fluid. This part of the procedure lasts only a few minutes. After the sample is taken, another ultrasound check will be done.
Some women say amniocentesis doesn’t hurt at all, while others say they feel pressure or cramping.
Often, people find that the waiting period for the test results is the most difficult part of the procedure.
Since it was developed in the late 1960s, genetic amniocentesis has been performed on hundreds of thousands of pregnant women. Though it is now a routine procedure, it does have some risks:
Some women experience soreness or mild cramping for a day or so after the procedure. Spotting or vaginal bleeding may also occur.
We recommend that you take it easy for the next 24 hours. If you are on your feet a lot, we encourage you to take off for two days or alter your home and/or work schedule to allow you to sit. We can provide documentation of these recommendations for your employer. If you have questions or symptoms that are of concern to you after your amniocentesis, please contact us. We particularly ask you to watch for severe cramping, increasing bleeding, leakage of clear fluid, increasing soreness or tenderness in the abdomen and/or fever.
If any of these symptoms occur, please call your obstetrician or the Maternal Fetal Care Center at 414-805-6624 and ask to speak to a nurse. If you are calling after hours, please call Labor and Delivery at 414-805-3939.
Testing for chromosomal abnormalities, such as Down syndrome, usually takes 10 to 14 days. Preliminary results may sometimes be available 24 to 48 hours after the procedure. Other specialized testing such as DNA testing or biochemical analysis may take longer.
We will call you and your physician or midwife with your results and will also send them a copy of your results.
If your results are abnormal, we will discuss them with you and additional testing that may be recommended.