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Amniocentesis
Amniotic fluid is the thin watery substance that surrounds the developing fetus in the uterus/womb. Amniocentesis involves removing a small amount (about 4 teaspoons) of this fluid with a needle, for testing in the lab. This test can be done after the 15th week of pregnancy. More information can be found below and on the Prenatal Genetic Screening Program website.
When do I come to the hospital?
Your doctor or midwife will book your test. If you have been booked at Women’s Diagnostic Ambulatory Program, you will receive a letter in the mail telling you when to come to the hospital.
Amniocentesis is also available at the following hospitals:
- Royal Columbian
- Surrey Memorial
- Victoria General
- Nanaimo
If one of these locations is more convenient for you, have your doctor or midwife schedule your test there.
You should have a light meal before coming to the hospital. No other special preparation is necessary.
Who will do my procedure?
A doctor who has completed special training in this procedure will perform your amniocentesis. A nurse and a sonographer (ultrasound technician) will be assisting.
Who should come with me?
It is advisable that you not drive yourself, or take public transportation (bus) after the test.
For this reason, we recommend that your partner, or another person of your choosing, accompany you for your test. If they do not wish to view the actual procedure, they may wait in the lobby, or sit just outside the procedure room. If you have to come alone, we recommend taking a taxi home, if possible.
Another adult must accompany children in case they need to be taken out of the procedure room.
What will happen?
Before having your test, a nurse will review the procedure with you, make sure you are aware of the available options, and answer your questions. She will obtain your written consent. You will receive information to take home about what to expect after your test.
It is not necessary for you to change your clothes. Wear something loose and comfortable that can be slipped down below your hips easily. Towels are used to help maintain your privacy and to protect your clothing.
Ultrasound is used to locate the baby and placenta. The baby’s heart rate is recorded before (and after) the procedure. Some measurements are taken to check the baby’s growth and to confirm your weeks of pregnancy. With the ultrasound picture on the screen, the doctor finds the safest and easiest place to insert the needle. An antiseptic solution is used to clean the skin. (The pink stain on your skin will wear off in a few days.) The needle is carefully guided to the selected spot and the small sample of fluid is withdrawn through the needle.
During the test, you may experience some cramping and a slight sensation of pressure. Most women find it no worse than having a blood test taken from their arm.
What can Amniocentesis detect?
Amniocentesis is a specific test that is able to tell you if your baby has a normal number of chromosomes (46). It can find Down syndrome and other major chromosome abnormalities. A second test is done to measure the amount of alpha-fetoprotein (AFP) in the amniotic fluid. A higher than normal amount may suggest the possibility of a neural tube defect, such as spina bifida. Normal results can take up to 3 weeks. Concerns are usually identified and given to your doctor or midwife within 10-14 days.
If there is a family history of a known problem, other special tests may be done on the amniocentesis sample. You need to discuss this with your doctor or midwife who will refer you to Medical Genetics for additional tests in advance of your procedure.
Five in 100 women have a chance of having a baby with a major birth defect that can be found during the first year of life. The most common defects are cleft lip and palate, clubfeet, heart defects and mental retardation. The results from amniocentesis, CVS or fetal blood sampling will indicate whether or not there are chromosome abnormalities or neural tube defects, but will not be able to rule out other abnormalities.
What are the risks involved in amniocentesis?
- Miscarriage: It is important to note that the risk of miscarriage unrelated to any procedure is about 6 in 100 at nine to twelve weeks of pregnancy, decreasing to 1 in 100 by the fifteenth week of pregnancy. Following amniocentesis, there is an additional risk that 1-2 in 200 women will have a miscarriage (1-2 in 100 for twin pregnancy). Also, 2 in 100 women will have problems, such as amniotic fluid leakage or bleeding.
- Damage to the Fetus: It is rare for the needle to touch the fetus because ultrasound is used as a guide, and the needle can be moved in another direction. Sometimes amniocentesis must be repeated because the cells do not grow in the laboratory, or there are not enough cells in the fluid sample.
- Bleeding, Cramping or Infection: Cramping during or following the procedure is not uncommon and usually gets better with rest. Small amounts of bleeding or amniotic fluid leakage may occur following the procedure. Infection following amniocentesis rarely occurs, and would likely begin to show with a fever and flu-like symptoms.
What happens after my procedure?
You do not need to stay in the hospital following your test.
We recommend that you rest for the next 24 hours. You do not have to go to bed; resting on the couch or in a reclining chair is fine. Avoid heavy lifting and use the time to relax with a favourite book, video, etc. If you need a note to be off work, the doctor who does your procedure will sign it for you.
If you have come from outside Vancouver, you may want to stay somewhere overnight. If this is not an option for you, take it easy (e.g., use the elevator on the ferry or the cart to get to your departure gate at the airport, take stretch and bathroom breaks if you are driving a longer distance).
We will provide you with written information about what to watch for and how to contact us if you have any concerns. Mild cramping is the most common side effect, and it should go away over the next twenty-four hours.
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