Amniotic fluid surrounds the baby during pregnancy. Amniocentesis is the removal of a small amount of this fluid for testing.

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Amniocentesis is most often done to see if there is an abnormality in your baby's genes (DNA). It can also be done to see if your baby is developing correctly. Later in pregnancy, it can be done to determine the maturity of your baby's lungs.

Factors that indicate that you may need this procedure include:

  • Age: over 35 years at the time of delivery
  • Family history of chromosome abnormality
  • Family history of inherited disorder
  • Family history of neural tube defect—problems in spine and brain growth, such as spina bifida or anencephaly
  • Abnormal results from early screening tests for chromosomal abnormalities

Depending on your risk factors, cells in the amniotic fluid are tested for:

  • Chromosome abnormalities. The results are usually ready within 14 days. Missing or extra chromosomes lead to physical birth defects and intellectual disability. Down's syndrome is one example.
  • Inherited genetic diseases—Test results are usually ready in 1-5 weeks. Examples include:

Amniocentesis may also be done:

  • In high-risk pregnancies that may require early delivery
  • There is concern for Rh-sensitization pregnancy