Amniocentesis is a test during pregnancy. It removes a small amount of the fluid that surrounds the baby for testing.
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Reasons for Procedure
This procedure is done on those at high risk after 15 weeks of pregnancy. It tests cells in the fluid to look for signs of:
- Missing or extra chromosomes that may point to a birth defect and/or intellectual disability such as Down syndrome
- Birth defects of the brain, spine, or spinal cord
- Inherited genetic diseases, such as: sickle cell disease, Cystic fibrosis, and Tay-Sachs disease
- Fetal anemia
This test may also be done to make sure the baby's lungs are growing as expected.
Problems are rare, but all procedures have some risk. The doctor will go over some problems that could happen, such as:
- Bleeding, cramping, and fluid leaking from the vagina
- Mixing of blood if the mother and baby have different blood types
- Need for repeat testing
- Harm to the fetus by the needle—rare
Things that may raise the risk of problems are:
- Obesity in the mother
- Prior abdominal surgery
What to Expect
Prior to Procedure
The healthcare team may meet with you to talk about:
- Anesthesia options
- Any allergies you may have
- Current medicines, herbs, and supplements that you take and whether you need to stop taking them before the procedure
- Whether you need a ride to and from the procedure
The doctor will give you a local anesthesia. The area will be numbed.
Description of the Procedure
An ultrasound will be used during the procedure. This will let the doctor see where the needle is. The belly will be cleaned. A very thin needle will be inserted through the skin and into the uterus. A few teaspoons of amniotic fluid will be removed. The needle will be removed. The doctor will make sure that the baby's heartbeat is normal.
How Long Will It Take?
About 45 minutes
Will It Hurt?
Cramps and light bleeding are common in the first few hours after the test.
At the Care Center
Right after the procedure, the staff may:
- Monitor the baby
- Ask you to rest on your left side
Rest will be needed in the first 24 hours before going back to activities. The health team will call with the test results.
Call Your Doctor
Call the doctor if you are not getting better or you have:
- Signs of infection, such as fever and chills
- Nausea or vomiting
- Pain or cramping in the belly
- Blood or fluid leaking from the vagina
- Redness, swelling, increasing pain, excessive bleeding, or discharge from the amniocentesis site
- New or worsening symptoms
If you think you have an emergency, call for medical help right away.
American Congress of Obstetricians and Gynecologists
American Pregnancy Association
Canadian Women's Health Network
The Society of Obstetricians and Gynaecologists of Canada
Chorionic villus sampling: CVS. American College of Obstetricians and Gynecologists website. Available at: http://americanpregnancy.org/prenatal-testing/chorionic-villus-sampling. Accessed July 21, 2020.
Delaney M, Matthews DC. Hemolytic disease of the fetus and newborn: managing the mother, fetus, and newborn. Hematology Am Soc Hematol Educ Program. 2015;2015:146-151.
Hemolytic disease of the fetus and newborn (HDFN). EBSCO DynaMed website. Available at:https://www.dynamed.com/condition/hemolytic-disease-of-the-fetus-and-newborn-hdfn. Updated December 20, 2019. Accessed July 21, 2020.
Routine prenatal care. EBSCO DynaMed website. Available at:https://www.dynamed.com/management/routine-prenatal-care-36. Updated January 21, 2020. Accessed July 21, 2020.
Last reviewed January 2021 by EBSCO Medical Review Board Elliot M. Levine, MD, FACOG Last Updated: 3/12/2021