What is amniocentesis?

Amniocentesis is a procedure performed during pregnancy to examine a baby's chromosomes. Most often, an amniocentesis is done between 16-20 weeks of pregnancy (gestation). During this procedure, amniotic fluid is removed for testing. The amniotic fluid contains cells that the baby has naturally shed. Cells and proteins within the amniotic fluid are examined in the lab to test for specific fetal disorders. Alpha-fetoprotein (AFP) is also found in the amniotic fluid and can be measured in the laboratory. The entire amniocentesis appointment lasts approximately 45 minutes -- most of which involves a detailed ultrasound examination.

Do I need to have an amniocentesis?

Amniocentesis is offered if:

  • you will be 35 years old or more at time of delivery
  • you or your partner has a child or other family member with a chromosomal abnormality
  • you have a positive screening test result (for example nuchal screen, expanded AFP test)
  • you or your partner has a chromosomal rearrangement (for example, a translocation or an inversion)
  • you or your partner have an increased risk of having a child with a genetic disease for which testing is available
  • you or your partner has had a previous pregnancy or child with a neural tube defect (for example, spina bifida or anencephaly)

How do I prepare for an amniocentesis?

  • You will be given instructions on how much water to drink prior to your ultrasound test. A full bladder is necessary for the ultrasound procedure.
  • Do not take any aspirin or aspirin-containing products five (5) days prior to the Amniocentesis procedure, and do not take Heparin 24 hours prior to the amniocentesis procedure.

What can I expect during an amniocentesis?

  • First, the technician performs a detailed ultrasound examination. This takes about 30 minutes to complete. The technician checks the date of your pregnancy, screens for birth defects, checks the placenta, and evaluates the amniotic fluid levels.
  • Next, using ultrasound, the doctor chooses a "pocket," or area of amniotic fluid, for testing. Then, the doctor inserts a thin needle into the abdomen and uterus and removes a small amount of fluid (about one ounce). This part of the procedure lasts about 1-2 minutes.

Is there discomfort during an amniocentesis?

  • Most women experience minimal discomfort with an amniocentesis. Some women do experience cramping during and after the procedure; the cramping usually goes away after a short time.
  • Some women may also experience abdominal soreness at the site of the needle insertion. Note: Soreness at the needle insertion site usually goes away within a few hours, but may last a few days.

What can I expect after an amniocentesis?

  • After the procedure, you should go home to rest. You will be given a detailed instruction sheet on what to expect following an amniocentesis.
  • You may drive yourself home after an amniocentesis procedure. 
  • Generally, women may resume their regular activities the day after the amniocentesis procedure. We advise the following activity limitations after an amniocentesis:
  1. No lifting over 15 pounds for 24 hours.
  2. No strenuous exercise or strenuous work activity for 72 hours.
  3. No air travel for 72 hours.
  4. No intercourse for 24 hours.

Are there any risks associated with an amniocentesis?

  • Spotting, cramping and/or light bleeding (less than a menstrual period) may occur.
  • There is a natural miscarriage rate throughout pregnancy. An amniocentesis increases the natural rate of miscarriage. The most recent data shows that about 1 in 1,600 women may have a miscarriage as a result of the amniocentesis.

Read More: 
Ultrasound Guide for Pregnancy
Fetal Growth Calculator