AMNIOCENTESIS

When is amniocentesis performed?

Amniocentesis is usually performed between 14 and 20 weeks.

Amniocentesis can be used later in the third trimester for a few reasons. Your healthcare provider may recommend the procedure if your membranes have ruptured prematurely, in order to assess for uterine infections. Amniocentesis may also help determine the severity of fetal anemia in babies with Rh disease, and assist your physician determine whether the fetus requires lifesaving blood transfusions.

Amniocentesis is sometimes done to assess lung maturity. If so, this is done shortly before delivery.

What does the amniocentesis test look for?

Amniocentesis detects chromosome abnormalities, neural tube defects, and genetic disorders. Down syndrome or Trisomy 21 is the most common chromosome abnormality. Genetic disorders include disorders such as cystic fibrosis. The most common neural tube defect is spina bifida.

Amniocentesis is occasionally used late in pregnancy to assess whether the baby’s lungs are mature enough for the baby to breathe on his own.

What do amniocentesis results mean?

Amniocentesis is a diagnostic test that detects chromosome abnormalities, neural tube defects and genetic disorders with high levels of accuracy (98-99%). Although the probabilities of identification are high, this test does not measure the severity of these birth defects.

Alpha-fetoprotein levels and advanced level ultrasounds may assist in assessing degree of disability that may be present.