PRENATAL DIAGNOSIS - Amniocentesis

Inside the uterus, amniotic fluid surrounds and protects your baby. The main source of amniotic fluid is fetal urine. By analyzing a small sample of amniotic fluid, we can learn many things. For example, amniotic fluid studies can detect conditions such as Down syndrome, trisomy 18, trisomy 13 and other genetic abnormalities. Your doctor and genetic counselor will explain the conditions that can and cannot be detected using amniotic fluid.

Amniotic fluid is removed from the uterus by a procedure called amniocentesis. Your doctor will use ultrasound to identify an appropriate pocket of amniotic fluid inside the uterus. Then, under sterile conditions, a very fine needle will be inserted into the amniotic fluid and about 20 ml (4 teaspoons) of amniotic fluid will be removed with a syringe. The needle is then removed. The procedure usually lasts about 30 seconds and your doctor will use ultrasound throughout the procedure to ensure safety. The amniotic fluid is then sent to the lab for testing. In most cases, you will be able to resume your normal activities the next day. The 20 ml of amniotic fluid that are removed account for no more than 2-4% of the total fluid in the uterus and your baby will replenish it within a day. If your blood type is Rh negative, we will recommend that you have a RhoGam injection before leaving the office.

Bleeding, infection and miscarriage are uncommon after amniocentesis. The rate of miscarriage is less than 1%.

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