Understanding Amniocentesis

Reviewed by James Brann, MD

Amniocentesis

Amniocentesis is a procedure when a doctor takes amniotic fluid from a woman’s pregnant belly. This type of fluid is what surrounds a fetus inside the woman’s uterus. Once your doctor has the small sample, he or she tests it to find out more about the fetus.
There are generally two common reasons why this is done. The first is to discover if the fetus has Down syndrome, or another genetic problem. It may be performed if a mother’s blood test or ultrasound has already shown a possible genetic problem with her unborn child. Testing is also sometimes done to find out if a child will have the ability to breathe on its own if the baby is born earlier than its mother’s due date.

Amniocentesis can be done after a woman hits week 15 of pregnancy. It is dependent, though, on why your doctor needs to test the amniotic fluid.

Steps of Amniocentesis

  • An ultrasound - Your doctor uses this to see moving pictures of the fetus, a woman’s uterus and the amniotic fluid. It appears on a screen similar to a television.
  • Needle Insertion - A doctor watches the ultrasound screen while inserting a needle into a mother’s belly, and then on into the amniotic fluid.
  • Fluid removed - Your doctor next uses the needle to remove a small amount of amniotic fluid. The test will remove anywhere from one to two tablespoons, then this will go to the lab for testing.

Risks with Amniocentesis

While problems are rare with amniocentesis, they do happen. These may include:
  • Needle touches baby - In rare cases, this may cause injury.
  • Blood leakage from placenta into mother’s bloodstream - The placenta brings nutrients and oxygen to your baby, and is also the organ which carries waste away. This leakage may cause problems in future pregnancies.
  • Amniotic fluid leakage -This may lead to an infection, which could lead to a miscarriage in early pregnancy, preterm labor or a preterm birth later on. A preterm birth signifies your baby was born prior to week 37 of pregnancy.

Symptoms to call a doctor about

Whether you call you doctor depends on how bad your symptoms are, and what they are. After a woman has amniocentesis, it is common to experience mild belly cramping. You should call your doctor, though, if:
  • Cramps are getting worse
  • You have a fever of more than 100.4 degrees Fahrenheit or 38 degrees Celsius
  • You have leaking vaginal fluid or vaginal bleeding


If tests do show a genetic problem with your fetus, make sure you speak with a genetic counselor. You’ll also want to consider doing this before testing. A counselor may be able to help you with your feelings and help you make a decision about what to do next.



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