woman sitting in bed and looking at her ultrasound picture

What to Know About the Amniocentesis Test

By Erica Patino
Reviewed by Alyssa Quimby, M.D.
June 21, 2023

When you’re in the first half of your pregnancy, you may hear your doctor or midwife talk about a prenatal test called amniocentesis. The amniocentesis is often called an amnio for short. It’s optional and it’s only suggested in some cases because it comes with some risks.

What Does Amniocentesis Mean?

Amniocentesis is a test that can help doctors detect certain birth defects or genetic problems in a developing baby. It’s generally done between 15 and 22 weeks of pregnancy. During the test, a healthcare provider will use ultrasound to find your baby in your uterus. They will insert a thin needle through the wall of your stomach in order to take out a small amount of amniotic fluid. This is the fluid that surrounds the baby in your uterus. Doctors then test the fluid for abnormalities with the chromosomes, such as Down syndrome, spina bifida, and cystic fibrosis.

What Is the Risk of Amniocentesis?

There is a 1 in 900 chance of miscarriage or other problems from an amniocentesis, according to the Mayo Clinic.

Before amniocentesis is done, a doctor will often suggest you have a different test that is less risky. “If someone has a screening test called a non-invasive pregnancy test (NIPT) and it's concerning for a chromosome problem, we offer either a CVS [chorionic villus sampling] if they're early enough, or an amniocentesis, to make sure that the diagnosis is correct,” says Teresa Hoffman, M.D., a board-certified ob-gyn at Hoffman and Associates OB/GYN in Baltimore.

Who Should Consider Amniocentesis?

The most common reason someone might consider getting the test done is their age. That’s because the risk of chromosomal abnormalities increases with age. “A pregnant person might get it if they are age 35 or older, or if doctors suspect a chromosomal abnormality based on an early ultrasound, or in case one of the parents is a carrier of a genetic defect,” says Kimberly Langdon, M.D., a board-certified ob-gyn at Medzino based in Ohio.

According to the American Medical Association Journal of Ethics, about 5-10% of pregnant people choose to have the test.

What Do the Results Mean?

If the baby’s chromosomes seem normal, then doctors will do more ultrasounds and tests to see if anything else is going on.

If the chromosomes look abnormal, it may become a decision for the parents, depending on the state they live in, whether they want to stay pregnant or not. “But the amniocentesis isn't done to look for a reason to terminate a pregnancy,” says Hoffman. “It's done to look for cause for something we're seeing, to try to manage the baby to the best outcome.”

For some parents, knowing their baby has a health concern allows them to learn more about the condition and what their future baby’s health needs will be. It may also give them time to learn more about raising a child with special needs.

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