There are risks to amniocentesis. Do I need an amnio?


Most women will have normal, healthy children and will not require invasive prenatal tests. However, all women have a 3 percent chance that their child will have a birth defect; this is the risk that any woman faces with a pregnancy, regardless of age. Do you need an amnio to determine this risk?

Amniocentesis: what is it? Why might you need an amnio?

Amniocentesis is a procedure to remove a small amount of fluid from the amniotic sac that surrounds the fetus. This fluid is then used for testing. A doctor may offer an amnio for consideration in any of these situations:

  • A woman has a family history of genetic disorders or is concerned about her risk of chromosome abnormalities such as Down syndrome. Or, she’s had a previous child with certain birth defects or genetic disorders.
  • Mom-to-be has had a maternal serum screening either in the first or second trimester which indicates an increased risk of Down syndrome or spina bifida.
  • An ultrasound indicates a structural malformation.

Amniocentesis is usually performed at 15-22 weeks of pregnancy. The risk of complications with early amniocentesis (12-14 weeks) has been slightly higher than standard amniocentesis (15-18 weeks) and is not routinely offered.

During the amnio, a thin needle is placed through the mom-to-be’s abdomen and into the amniotic sac in a location away from the fetus. During the procedure, an ultrasound visualizes the needle placement and fetal position throughout the entire procedure. The sensation is similar to having blood drawn, although the expectant mother may experience mild cramping afterward. The doctor draws 1-2 tablespoons of amniotic fluid–though not to worry, baby replaces these fluids within 24 hours. After the withdrawal, the healthcare team will analyze the fetal cells and proteins within the collected fluid. Test results are usually available within 1-2 weeks.

What to do after an amnio

After the amniocentesis, your doctor will advise you to avoid strenuous physical activity (e.g., heavy lifting, sports, etc.) for 24 hours. Some women return to work if no physical activity is involved.  However, it is ideal to relax and have a quiet day as, emotionally, the procedure can be draining. If you have any questions about what activities are safe post-amnio, talk to your physician or genetic counselor.

Know the risks

There are risks associated with the procedure, so it’s not surprising that some women ask, “Do I need an amnio?” It’s important for women to know that there is a risk associated with amniocentesis. Miscarriage or major complications occur in 1-in-200 to 1-in-400 pregnancies. These complications include bleeding, leakage of amniotic fluid, and infection. Some women may experience cramping or discomfort after the procedure, although most women will experience no problems.

More information:

Louise E. Wilkins-Haug, MD, PhD, is the Division Director of Maternal Fetal Medicine and Reproductive Genetics at Brigham and Women’s Hospital

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