When you’re pregnant, the words “test” or “procedure” may sound alarming. Rest assured, you’re not alone. But learning why certain things are recommended and how they’re done can be really helpful.

Let’s unpack what amniocentesis is and why you might choose to have one.

Remember that your doctor is a partner in this journey, so tell them about any concerns and ask as many questions as you need.

Amniocentesis is a procedure in which your doctor removes a small amount of amniotic fluid from your uterus. The amount of fluid removed is typically no more than 1 ounce.

Amniotic fluid surrounds your baby in the womb. This fluid contains some of your baby’s cells and is used to find out if your baby has any genetic abnormalities. This type of amniocentesis is usually performed in the second trimester, typically after week 15.

It can also be used to determine if your baby’s lungs are mature enough to survive outside the womb. This type of amniocentesis would occur later in your pregnancy.

Your doctor will use a long, thin needle to collect a small amount of amniotic fluid. This fluid surrounds and protects the baby while they’re in your womb.

A laboratory technician will then test the fluid for certain genetic disorders, including Down syndrome, spina bifida, and cystic fibrosis.

The test results can help you make decisions about your pregnancy. In the third trimester, the test can also tell you whether or not your baby is mature enough to be born.

It’s also helpful for determining whether you need to deliver early to prevent complications from your pregnancy.

Abnormal prenatal screening test results are one common reason you might consider amniocentesis. Amniocentesis can help your doctor confirm or deny any indications of abnormalities found during the screening test.

If you’ve already had a child with a birth defect or a serious abnormality of the brain or spinal cord called a neural tube defect, amniocentesis can check whether your unborn child also has the condition.

If you’re 35 years or older, your baby is at a higher risk for chromosomal abnormalities, such as Down syndrome. Amniocentesis can identify these abnormalities.

If you or your partner is a known carrier of a genetic disorder, such as cystic fibrosis, amniocentesis can detect whether your unborn child has this disorder.

Complications during pregnancy might require you to deliver your baby earlier than the full term. A maturity amniocentesis can help determine if your baby’s lungs are mature enough to allow your child to survive outside of the womb.

Your doctor may also recommend an amniocentesis if they suspect that your unborn child has an infection or anemia or they think you have a uterine infection.

If it’s necessary, the procedure can also be done to decrease the amount of amniotic fluid in your womb.

This test is an outpatient procedure, so you won’t need to stay in the hospital. Your doctor will first perform an ultrasound to determine the exact location of your baby in your uterus.

An ultrasound is a noninvasive procedure that uses high-frequency sound waves to create an image of your unborn baby. Your bladder must be full during the ultrasound, so drink plenty of fluids beforehand.

After the ultrasound, your doctor may apply numbing medication to an area of your belly. The ultrasound results will give them a safe location to insert the needle.

Then, they’ll insert a needle through your belly and into your womb, withdrawing a small amount of amniotic fluid. This portion of the procedure usually takes about 2 minutes.

The results of genetic tests on your amniotic fluid are usually available within a few days.

The results of tests to determine the maturity of your baby’s lungs are usually available within a few hours.

Amniocentesis is usually recommended between 16 to 20 weeks, which is during your second trimester. Although complications can occur, it’s rare to experience the more severe ones.

The risk of miscarriage is up to .3 percent if you have the procedure during the second trimester, according to the Mayo Clinic. The risk is slightly higher if the test occurs before 15 weeks of pregnancy.

Complications associated with amniocentesis include the following:

  • cramps
  • a small amount of vaginal bleeding
  • amniotic fluid that leaks out of the body (this is rare)
  • uterine infection (also rare)

Amniocentesis can cause infections, such as hepatitis C or HIV, to transfer to the unborn baby.

In rare cases, this test may cause some of your baby’s blood cells to enter your bloodstream. This is important because there’s a type of protein called the Rh factor. If you have this protein, your blood is Rh-positive.

If you don’t have this protein, your blood is Rh-negative. It’s possible for you and your baby to have different Rh classifications. If this is the case and your blood mixes with your baby’s blood, your body may react as if it were allergic to your baby’s blood.

If this happens, your doctor will give you a drug called RhoGAM. This medication will prevent your body from making antibodies that will attack your baby’s blood cells.

If the results of your amniocentesis are normal, your baby most likely doesn’t have genetic or chromosomal abnormalities.

In the case of maturity amniocentesis, normal test results will assure you that your baby is ready to be born with a high likelihood for survival.

Abnormal results may mean there’s a genetic problem or chromosomal abnormality. But that doesn’t mean it’s absolute. Additional diagnostic tests can be done to get more information.

If you’re unclear about what the results may mean, don’t hesitate to ask your healthcare provider. They can also help you gather the information you need to make a decision about next steps.