Your baby is surrounded by amniotic fluid, a substance much like water. Amniotic fluid contains live fetal skin cells and other substances, such as alpha-fetoprotein (AFP) – which provides important information about your baby's health before birth.
During an amniocentesis, you doctor will obtain a small sample of the amniotic fluid to diagnose chromosomal disorders such as Downs Syndrome, and open neural tube defects (ONTDs) such as spina bifida. Testing is available for other genetic defects and disorders depending on the family history.
Who Should Have an Amniocentesis?
An amniocentesis is generally offered to women between the 15th and 20th weeks of pregnancy who are at increased risk for chromosome abnormalities. An amniocentesis may be recommended for you if you:
Are of advanced maternal age (35 years or older)
Had an Abnormal AFP (alpha fetoprotein) blood test
What Happens During an Amniocentesis?
Your doctor will insert a long, thin needle through your abdomen into the amniotic sac to withdraw a small sample of the fluid. Although specific details of each procedure vary slightly, generally, an amniocentesis follows this process:
The abdomen is cleansed with antiseptic
The doctor may administer a local anesthetic to numb the skin
An ultrasound is used to help guide a hollow needle into the amniotic sac
A small amount of fluid is withdrawn for laboratory analysis
If you have an amniocentesis, avoid any strenuous activities for at least 24 hours. You may also feel some cramping during or after the procedure. Twins or other multiples require sampling from each amniotic sac.
Following the amniocentesis, the fluid is sent to a genetics laboratory so that the cells can grow and be analyzed. Results are usually available in about 10 days to two weeks, depending on the laboratory.