Amniocentesis (also called amnio) is a
common prenatal test used to diagnose certain
birth defects and
genetic abnormalities. Genetic abnormalities are changes in genes that are passed down to a baby from mom and dad. They may cause health problems for a baby.
Amnio is different from another prenatal test called
chorionic villus sampling (CVS). Talk to your provider about having an amnio, CVS or other prenatal tests.
The American College of Obstetricians and Gynecologists (ACOG) recommends that all pregnant women should have the option of having prenatal tests like amniocentesis. They may recommend you have the test if you are at risk for having a baby with birth defects. Most women who have the test find out their baby is fine.
During the test, your health care provider takes a small sample of amniotic fluid (fluid that surrounds your baby). The sample is used to check your baby’s health.
It’s best to have an amnio in the second trimester between 15 and 20 weeks of pregnancy. Amniocentesis before 15 weeks is no longer recommended because it has a higher risk of
miscarriage and other complications. A third-trimester amniocentesis can find infections in your uterus (womb) or check to see if your baby’s lungs are developed enough for
early birth.
Your provider should offer you an amnio, and you can ask to have one. You may want to have an amnio if you’re at risk for having a baby with a birth defect. These risks include:
- Being 35 or older: The risk of having a baby with certain birth defects, such as Down syndrome, increases as you get older.
- Having a previous child or pregnancy with a birth defect: If you had a child or a pregnancy with a birth defect in the past, your provider should offer you testing.
- Abnormal screening test results: If you have abnormal results from a screening test, your provider should offer you amniocentesis. Most babies with abnormal screening test results are born healthy.
- Family history of a genetic condition: If you or your partner has a certain genetic disease (a health condition that gets passed down to a baby from mom or dad), or a close family member with a disease such as cystic fibrosis or sickle cell disease you may want to have the test.
Amniocentesis takes a few minutes.
First, your health care provider uses ultrasound to find your baby, the placenta and pockets of amniotic fluid. He then cleans your belly with an antibacterial liquid that destroys germs on your skin. He asks you to lie flat on your back.
Next, using ultrasound as a guide, your provider puts a thin needle through your belly and uterus into the amniotic sac. He uses the needle to remove about 1 to 2 tablespoons (1 ounce) of fluid.
Once the fluid sample is taken, your health provider uses the ultrasound to check that your baby’s heartbeat is healthy. Your baby’s amniotic fluid sample is sent to a lab, where it is examined and tested.
In the lab, cells shed by your baby are separated from the amniotic fluid. If your baby is being tested for genetic problems, the cells are grown for about 10 to 12 days at the lab so that there are enough cells to check for problems. These test results usually are available within 2 weeks.
The lab also may test your baby’s amniotic fluid for proteins like alpha-fetoprotein (AFP). Measuring the amount of AFP can check if your baby has neural tube defects (NTDs). The neural tube is the part of a developing baby that becomes the brain and spinal cord. AFP levels are often higher if your baby has an NTD. AFP test results usually are available in a few days.
Some women find that the test is painless. Others feel cramping when the needle enters the uterus, or pressure when the fluid is removed. One to 2 out of 100 women have cramping, spotting or leaking amniotic fluid after the test. Your provider may tell you to avoid intense activity and take it easy for the rest of the day.
Serious complications from amniocentesis are rare. However, the test does involve a small risk of
miscarriage. According to ACOG, less than 1 in 200 women have a miscarriage after amniocentesis.
In most cases, amnio test results show that a baby is healthy and without birth defects. If the test shows that your baby does have a birth defect, talk to your provider about your options. For example, your baby may be able to be treated with medicines or even surgery before birth. Or there may be treatments or surgery he can have after birth. Knowing about a birth defect before birth may help you get ready emotionally to care for your baby. You also can plan your baby’s birth with your health care provider. This way, your baby can get any special care she needs right after she is born.
Choosing to have an amniocentesis is a personal decision. Talking with
genetic counselors, your health care provider, and religious and spiritual leaders can help you make decisions about testing for birth defects during pregnancy.
Ask your provider about other prenatal test options and how you can find a doctor who is trained and experienced in offering specific tests. Learn as much as you can about any prenatal tests your provider recommends to make the right decisions for you and your baby.
How can you reduce risk of birth defects?
An amnio can diagnose certain birth defects during pregnancy. There are things you can do on your own before and during pregnancy to help reduce your risk for birth defects. Here’s what you can do to improve your chances of having a healthy pregnancy and a healthy baby:
May 2011