Prenatal Test - Amniocentesis - How it is performed and when?

Amniocentesis is a prenatal test that is usually performed during weeks 15 to 18 of pregnancy. This test is performed to detect many different defects and disorders, but most commonly it is used to detect chromosomal defects such as Down syndrome.

To begin with you’ll most likely have a detailed ultrasound to measure the baby and to do an anatomical survey. You may have your ultrasound a few days ahead of the amniocentesis. During the procedure, you’ll lie on a table and have your abdomen cleaned with antiseptic such as alcohol or iodine. Usually you can have someone stay with you during the procedure, check with your doctor or midwife on the guideline for this. After your abdomen is cleaned a pocket of amniotic fluid will be located using ultrasound. This part of the test can take a while, because they want to locate fluid that is far enough away from the baby and placenta. While the ultrasound continues for guidance a long, thin, hollow needle will be inserted through your abdominal wall and into the sac of fluid around the baby. About one ounce of fluid will be removed and then the needle will be removed. The actual withdrawal of fluid should take less than 30 seconds.

During this procedure you may feel some discomfort, including cramping, pinching, or pressure. You may opt to have your abdomen numbed with a local anesthetic during the procedure. After the procedure is complete your doctor may listen to the baby’s heartbeat to make sure everything is well. You’ll want to take it easy for the rest of the day and avoid strenuous activity for the next couple of days. You may have some minor cramping for one or two days, but if you have significant cramping, spotting or are leaking fluid you should call your doctor or midwife.

Each pregnancy, expectant mother, and unborn child is different. Your pregnancy may not progress the same as the information found here. The information here is based on the average pregnancy. It's not meant to be a replacement for any advice your may receive from your doctor. If you have any concerns about your pregnancy, we advise you to contact your doctor.