Pregnancy Home > Amniocentesis: Answers to the Most Commonly Asked Questions

An amniocentesis can be a valuable medical procedure, giving you information about certain medical conditions your baby may have or be at risk for. A certain amount of risk is involved, but this is generally low, and the procedure is often over in 45 minutes. The results are extremely accurate. Talk to a genetic counselor or your healthcare provider about whether it is necessary for your particular situation.


What Is an Amniocentesis?

While in the womb, your unborn baby is surrounded by a clear liquid known as amniotic fluid. The amniotic fluid, which helps to cushion and protect your baby, contains fetal cells and other substances from your baby, such as urine and secretions. This material can be used to learn certain things about your baby, such as whether he or she has birth defects or other problems.
An amniocentesis is a procedure during which a small amount of amniotic fluid is removed from the uterus and tested to gain information about the developing fetus. Although it can be done any time after the eleventh week of pregnancy, most women have the procedure when they're 15 to 17 weeks pregnant.

Why Is It Done?

The American Congress of Obstetricians and Gynecologists (ACOG) recommends that all pregnant women be given the option of having screening tests, such as an amniocentesis. However, the procedure does carry some risks, so it's usually only recommended in certain situations.
The most common reason a woman has an amniocentesis is to determine whether her baby has a genetic or chromosomal condition, such as Down syndrome. Even then, it's only recommended for certain women who have a high risk for these situations. This might include women who:
  • Are 35 years old or older, since the risk for having a baby with a chromosomal condition increases with age
  • Had an abnormal screening test or ultrasound to help rule out or confirm any abnormalities
  • Have a genetic disorder, a partner with a genetic disorder, or a family history of genetic disorders
  • Have had a previous child or previous pregnancy affected by birth defects or genetic disorders.
An amniocentesis won't be able to detect all possible problems with your baby. For example, if your baby has a heart defect, it won't be picked up during this procedure. However, if your baby is at risk for certain problems, your healthcare provider can look for them with an amniocentesis. Some of the disorders that it can detect include:
Checking for genetic or chromosomal abnormalities isn't the only reason a healthcare provider may recommend an amniocentesis. Some other reasons a woman may have the procedure are to:
  • Determine if the baby's lungs are mature enough for delivery, which is important if early delivery is being considered
  • Check for infection in the fetus
  • Evaluate the degree of anemia in babies who have Rh sensitization, a condition that can occur if your blood is not compatible with your baby's blood
  • Remove excess amniotic fluid if there is too much.
Written by/reviewed by:
Last reviewed by: Arthur Schoenstadt, MD
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