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Amniocentesis is a prenatal test that doctors recommend for some pregnant women before they give birth. Also known as amnio, amniocentesis checks your baby for birth defects and genetic conditions.
If you decide to have amniocentesis, you can count on UPMC for safe, accurate testing during your pregnancy.
Amniocentesis is the most common invasive test doctors perform on pregnant women. The main reason doctors use amniocentesis is to diagnose birth defects and genetic conditions.
These include:
During this test, a doctor inserts a very thin needle into your belly (abdomen) and uterus (womb). They use an ultrasound to guide the needle to the sac surrounding your baby in your uterus. The needle withdraws a very small amount of amniotic fluid, which the doctor sends to a lab for testing.
Amniotic fluid contains cells that the fetus has shed as it grows. These cells can tell doctors if your baby has missing, damaged, or extra chromosomes (a group of DNA that contains genetic material), or has genetic mutations.
Though it's rare, doctors also use amniocentesis to check fetuses for infections as well as to treat a condition called polyhydramnios. With polyhydramnios, there’s too much amniotic fluid in the uterus, doctors use amniocentesis to take out some of the extra fluid.
Amniocentesis is optional — it’s your choice whether to have it or not. Your ob-gyn will talk to you about your risk factors, such as your age and a family history of certain conditions. They’ll also talk to you about the different conditions you might want to check for.
In most cases, you’ll get amniocentesis test results back in a few weeks. They're usually accurate, but your baby could be born with a condition that amniocentesis doesn’t check for.
Your doctor or a genetic counselor will talk to you about your test results and what they could mean for your baby. If your amniocentesis was positive for a certain condition, your doctor will also talk to you about your and your baby’s needs and care plans.
Doctors usually recommend amniocentesis between 15 and 20 weeks of pregnancy. But you can have the test any time between 15 weeks and right before you give birth.
Your doctor may recommend amniocentesis if you:
Some people choose not to have this optional test even if their doctors recommend it. If you have concerns about amniocentesis, share them with your doctor. They can answer any questions you have and tell you if other screening tests might be helpful.
Before you have amniocentesis, it's often helpful to consider what you might do if you receive a positive test result. For example, some parents want to make medical plans for their baby in advance.
Some people choose to have chorionic villus sampling (CVS) instead of amniocentesis. You can have CVS testing earlier in your pregnancy than amniocentesis. Doctors usually perform it between 10 and 13 weeks of pregnancy.
Your doctors may recommend you consider CVS if you:
With CVS, doctors take a sample of tissue from your placenta. Like amniocentesis, they use the sample to test for chromosome issues and birth defects.
CVS comes with a higher risk of miscarriage compared to amniocentesis.
Amniocentesis is a safe procedure. But it does come with some risks.
These include:
Your doctor will talk to you about the risks of amniocentesis. In some cases, they may recommend you receive testing for blood infections like HIV before amniocentesis.
If you decide to have amniocentesis, your doctor or another specialist will perform it. Amniocentesis is an outpatient procedure, and you’ll likely have the procedure at a doctor’s office or medical center.
In most cases, you don’t have to do anything to prepare to have an amnio. You can eat and drink as usual, but your doctor may ask you not to pee before the procedure. It can sometimes be easier to have amniocentesis when your bladder is full.
Amniocentesis might be a little uncomfortable, and it’s normal to feel emotional during the procedure. It can help to bring a partner or trusted friend or family member with you to your amniocentesis appointment. You’ll also need someone to drive you home after the procedure.
Amniocentesis doesn’t take long — the actual procedure usually lasts about 10 minutes. But your doctor may do an ultrasound before the procedure.
They may also watch you for up to an hour afterward, especially if you’re experiencing symptoms like cramping or bleeding. Ask your doctor’s office what to expect and how long your appointment will take.
Amniocentesis is an outpatient procedure. Doctors don’t use anesthesia, so you’ll be awake during the procedure.
Before your amnio, a nurse or doctor will clean your belly (abdomen) with antiseptic. They may use an injected medication (local anesthetic) to numb your skin.
Your doctor will use an ultrasound to guide a long, thin needle through your abdomen into the amniotic sac in your uterus. Then they’ll use the needle to take out a very small amount of liquid (amniotic fluid) from the sac.
If you have twins, triplets, or other multiple pregnancies, doctors will take fluid from each amniotic sac.
Your doctor will send the amniotic fluid from your amniotic sac to a lab for testing.
Amniocentesis shouldn’t be painful, but it’s normal to feel uncomfortable during the procedure. You might feel pressure or period-like cramping when the doctor pulls the needle out. You might have some mild pain and cramping afterward, too.
Your doctor will keep an eye on you for up to an hour after your amniocentesis prenatal test. They’ll be watching for any sharp or severe pain or heavy bleeding.
Light vaginal bleeding or spotting is normal after the procedure. You might experience mild period-like cramping or pain, too, which can last about a day after your test.
You’ll want to rest when you get home. It’s important to take it easy for at least 24 hours after your amniocentesis. You can do normal activities like walking, but don’t do anything strenuous, like lifting heavy objects or exercising.
If you’re in pain after your amniocentesis, talk to your doctor about taking an over the counter (OTC) pain medication. They may recommend acetaminophen (Tylenol). Don’t take ibuprofen (Advil) or aspirin, as these can thin your blood and increase bleeding.
Call your doctor right away if you experience any of these symptoms after your amniocentesis:
At UPMC, we understand that the decision to have an amniocentesis prenatal test is personal. Our ob-gyns, genetic counselors, and other experts are here to answer your questions. Our goal is to help you throughout your pregnancy so you can make choices that feel right for you.
By UPMC Editorial Staff. Last reviewed on 2024-09-05.
