Medical Content Created by the Faculty of the
Harvard Medical School
You wear a hospital gown and lie on your back on a table. An ultrasound is done to show the location of the fetus and placenta. Your lower abdomen is cleaned with an antibacterial soap. In some cases, the doctor uses a small needle to inject a numbing medicine just under the skin, so you do not feel the amniocentesis sampling needle later. (Because the sampling needle does not cause much more stinging than the numbing medicine itself, not every doctor includes this step.)
The hollow sampling needle is several inches long and is inserted through the skin and abdominal muscle and then through the wall of the uterus. A syringe attached to the needle is used to collect a sample of fluid.
The baby's heart tones and the mother's blood pressure and heart rate are checked at the beginning and end of the procedure. The whole procedure takes close to 30 minutes.