Amniotic fluid surrounds the fetus in the uterus and contains fetal cells and chemicals that can help determine certain types of birth defects. Genetic amniocentesis tests the amniotic fluid, typically between 16 and 18 weeks of pregnancy, for:
- Down syndrome
- Sickle cell disease
- Cystic fibrosis
- Muscular dystrophy
- Tay-Sachs disease
- Neural tube defects, such as spina bifida and anencephaly
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, including 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
- have a suspected uterine infection or Rh incompatibility
How is it performed?
Prior to amniocentesis, you will undergo an ultrasound so that we can determine your baby’s size, position and gestational age, and make sure there is enough amniotic fluid for the procedure. Guided by ultrasound, a 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 to draw a sample of amniotic fluid. The fluid is sent to the lab for a variety of tests that will give us more information about your pregnancy.
What happens afterward?
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 afterward to prevent you from producing antibodies against your baby’s blood cells.
You may experience tenderness where the needle was inserted and minor cramping (less than a menstrual period) after amniocentesis. 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 my results mean?
While not 100 percent accurate, a normal amniocentesis usually means there are no signs of any genetic defects in your baby. If your amniocentesis is abnormal, it may be a sign of a genetic disorder. No matter your results, our genetic counselors will meet with you to carefully and completely explain your options.