Amniocentesis is a prenatal test that takes a small sample of amniotic fluid (the fluid that surrounds the fetus during pregnancy).
This fluid contains cells shed by the fetus. The cells contain genetic information that can be tested for chromosomal disorders and open neural tube defects. Your doctor may recommend amniocentesis for any of the following reasons:
- Family history or previous child with a genetic disease or chromosomal or metabolic disorder
- Abnormal findings on prenatal ultrasound
- Risk of open neural tube defects like spina bifida or myelomeningocele
- Maternal age over 35 by the pregnancy due date
- Abnormal maternal screening test results
Complications from amniocentesis are rare, but do occur. There is a one in 300 or less risk of losing your pregnancy from the procedure, primarily due to the chance of rupturing membrane. Later in pregnancy, ruptured membranes can lead to preterm birth. There is also a small risk of infection inside the uterus.
Amniocentesis testing usually occurs during the second trimester, but can also be done in the third trimester. Before having an amniocentesis procedure, let your doctor know if you have a history of bleeding disorders or if you are taking blood-thinning medicine, as these may affect the procedure.
In rare cases, amniocentesis can cause some of the baby’s blood cells to enter the mother’s bloodstream. Let your doctor know if you are Rh negative. If this is the case and your baby is Rh positive, your body’s immune system may produce antibodies against your baby’s blood.
What to Expect
What to Expect
During amniocentesis, an ultrasound of the abdomen helps your doctor locate the uterus and the amniotic sac. Your abdomen is cleansed with antiseptic, and you should not touch the sterilized area during the procedure.
Using the ultrasound, the doctor guides a long, hollow needle into the abdomen, through the uterus and into the amniotic sac. You may feel a slight sting as the needle is inserted, and you may feel some cramping as it enters the uterus. The doctor withdraws a small amount of the amniotic fluid into a syringe, which may feel like a tugging sensation.
A sample of amniotic fluid is sent to a lab where specialists evaluate it for genetic or chromosomal abnormalities. The fluid can also be checked for a protein that is present when there is an open neural tube defect.
Returning Home
Returning Home
Do not do any strenuous activities for at least 24 hours afterward. Some cramping is normal, but let your doctor know if you experience any of the following symptoms:
- Bleeding or leaking of fluid
- A fever or chills
- Severe abdominal pain
- Changes in the activity level of the fetus if you are past 20-24 weeks
- Flu-like symptoms
It may take a week to 10 days to receive results. Our office will call you with the results when they are available. During the call, we can arrange further follow-up that may be needed.
Key Points to Remember
Key Points to Remember
- An amniocentesis is a prenatal test that draws amniotic fluid from the uterus by inserting a long, hollow needle.
- Amniotic fluid provides genetic information, drawn from cells shed by an unborn baby.
- When amniocentesis is performed, it is usually done in the second trimester of pregnancy.
- After amniocentesis is performed, you should not do any strenuous activity for at least 24 hours.
- Some cramping is normal afterward. If you notice other symptoms, you should report them to your doctor immediately.
Support Services & Resources
Support Services & Resources
These valuable resources can help expectant parents become more informed about prenatal tests such as amniocentesis.
Riley at IU Health offers a broad range of supportive services to make life better for families who choose us for their children's care.
This organization for physicians has information for patients about screening and diagnostic tests that may be performed during pregnancy.
This U.S. government website publishes information about many types of health conditions, tests and treatments, and includes a description of prenatal testing.
Visit this National Library of Medicine website to get information about genetic conditions and learn about various types of genetic tests.