What is amniocentesis?
Amniocentesis is a prenatal diagnostic test that can detect significant chromosome problems, such as Down syndrome, as well as small extra or missing pieces of chromosomes, called copy number variants. It can also identify genetic diseases like cystic fibrosis, sickle cell disease and Tay-Sachs disease in at-risk fetuses. Amniocentesis is typically performed between 15 and 20 weeks of pregnancy.
What happens during the procedure?
you will have an ultrasound to assess the location of the fetus and the placenta, and to evaluate fetal growth. The actual amniocentesis procedure takes about 10 minutes and is done under ultrasound guidance. A needle is inserted through the abdomen to remove a small amount of amniotic fluid. Most women do not find the procedure painful, although there may be some minor discomfort.
The cells from the fluid are then cultured and a karyotype analysis, an evaluation of the chromosomes, is performed. The amniotic fluid is also tested to determine if the fetus has a defect in the tube enclosing the brain and spinal column. The results are available in about two weeks.
Are there any risks associated with the test?
There is a small risk of miscarriage as a result of an amniocentesis.
What does a positive result mean?
If you have a positive result, this means the test found a genetic abnormality. In these instances, you will have a chance to discuss the diagnosis and your options with an obstetrical geneticist and a genetic counselor from the Prenatal Diagnosis Center, as well as your own doctor. Referrals and support information are available for all decisions.