Genetic Amniocentesis is a test of the amniotic fluid surrounding your unborn baby in the uterus. Amniotic fluid contains fetal cells and chemicals produced by the baby that, when analyzed, can help determine certain types of birth defects.
Genetic amniocentesis poses a small risk for you and your baby, so it is generally only offered to women who have significant risk for genetic disorders. That includes women who:
- Have an abnormal ultrasound or other prenatal screening test.
- Have a family history of certain birth defects or you or your partner is a known carrier of a genetic disorder.
- Have already had a child with a birth defect.
- Are 35 years of age or older.
- You have a suspected uterine infection or Rh incompatibility.
The test is usually performed between 16 and 18 weeks of pregnancy, and can be used to find:
- Down syndrome
- Sickle cell disease
- Cystic fibrosis
- Muscular dystrophy
- Tay-Sachs disease
- Certain neural tube defects such as spina bifida and anencephaly Before an amniocentesis, an ultrasound will be done to measure the size of the developing baby, the gestational age, the position of the baby and the placenta, and to be sure there is enough amniotic fluid
You will meet with our genetic counselor before the amniocentesis. The counselor will explain the procedure, the risks involved and possible results.
Guided by ultrasound, the physician will locate the fetus and placenta and then insert a thin, hollow needle through your abdomen and the wall of your uterus, into the amniotic sac but not too close to the baby. The physician will then take a sample of the fluid surrounding the baby into a syringe attached to the needle. The fluid is sent to the lab for a variety of tests that will give us more information about your pregnancy.
Amniocentesis may cause some of the baby's blood cells to enter your bloodstream. If you have Rh-negative blood, you will have blood taken before the procedure and will also receive a shot of Rhogam afterwards to prevent you from producing antibodies against your baby's blood cells.
You may experience:
- Some tenderness where the needle was inserted
- Some minor cramping (less than a menstrual period)
There is a slight risk of miscarriage, infection and amniotic fluid leakage as a result of the procedure. If you develop a fever or have bleeding, vaginal discharge or severe abdominal pain after your amniocentesis, please call your health care provider.
What do normal results mean?
A normal amniocentesis result means there are no signs of any genetic defects in your baby. Please note, however, that the test could miss some genetic defects. One of our genetic counselors will call you with the result of the amniocentesis.
What do abnormal results mean?
If your amniocentesis results are abnormal, it may be a sign of more than 200 disorders, including Down syndrome, hemoglobinopathies, and Tay-Sachs disease. If the amniocentesis results are abnormal, our genetic counselors will meet with you to carefully and completely explain what the results mean.