Amniocentesis is carried out to diagnose certain genetic conditions and abnormalities during pregnancy.
This procedure is performed under ultrasound guidance and involves using a needle to take a sample of amniotic fluid for testing. Amniotic fluid is the fluid that surrounds the baby in the uterus, and it contains some of the baby’s cells. The amniocentesis is performed from 15 weeks into pregnancy.
The test can diagnose chromosomal abnormalities in the baby. Down syndrome is the most common of these abnormalities. However, there are other chromosomal abnormalities which can be detected. If this is so, the implications of the abnormality for your baby will be discussed with you.
The test can also be used to diagnose several rare hereditary metabolic diseases. However, the laboratory procedures are very specific and are only performed if you are at high risk of having a baby with one of these conditions, after having been investigated by a Clinical Geneticist. Tests of this kind need to be arranged well before the date of amniocentesis, as special laboratory preparation is often required. The test does not prove the baby is normal. In every pregnancy there is a small but definite risk that the baby may have an abnormality. Chromosome abnormalities account for only 5% of these abnormalities. Therefore, a normal result of the test cannot rule out other problems (e.g. heart defects, cerebral palsy, autism, cystic fibrosis, club foot or cleft lip etc.)
Before Your Amniocentesis Test
If possible, please wear comfortable, loose-fitting clothing that allows easy access to the area that is being imaged. Two-piece clothing is ideal (separate upper/lower garments).
Please empty your bladder 2 hours before the appointment time, and then drink 600ml of water to fill your bladder and keep it full for the examination.
Arrange to have someone care for any young children for the whole day of your test.
When you visit Adelaide Women’s Imaging for an amniocentesis, you will be greeted at the desk by one of our friendly reception staff. They will confirm we have all the necessary consent forms and pathology results including your blood group. This procedure is performed in our medical rooms by an Adelaide Women’s Imaging Obstetrician and Gynaecologist. Admission to hospital is not necessary.
Before the procedure, a sonographer will take some images and measurements of your baby. Our doctor may also take some time to discuss the procedure with you. The procedure will begin once you are comfortably lying on your back. The doctor will then pass a fine needle through the lower abdominal wall into the uterus and amniotic sac and the amniotic fluid is withdrawn. After the procedure is complete the fluid is sent off for laboratory tests. A report with the results will be sent directly to your referring doctor from the labs.
After the procedure
On the day of the test, do not overexert yourself. A day off from work is recommended, no sport, intense exercise etc. Let your body guide you; if your abdomen is still tender or uncomfortable the following day, then continue to take things easy.
Some mild cramping abdominal pain, similar to period pain, can be expected. Rarely, a small amount of fluid loss may occur.
Should you be concerned about your symptoms please contact your Obstetrician or General Practitioner. Alternatively, you can phone our rooms on 8193 9522.
We allow 45 – 60mins. The actual test itself takes only 5-10 minutes; the preparation takes longer.
Frequently Asked Questions
How long does it take to get the results?
It depends on the reason for the amniocentesis.
FISH test (Fluorescent insitu hybridisation) is a rapid test taking 24-48 hours. It can give an answer about chromosomes 13, 18, 21, X and Y (the more common chromosomal abnormalities). This test has no Medicare rebate, and will attract a fee from the pathology lab.
The full results of the chromosomes take 7-10 days normally, although rarer genetic testing can take up to a few weeks to know the result.
What are the risks of an Amniocentesis?
International figures suggest the maximum risk of miscarriage due to the test is around 1:300.
However, many studies have shown that the skill of the operator greatly effects this number. All our obstetricians are highly qualified, and therefore the risk is much lower.
What are the risks that could occur?
A degree of cramping is to be expected after the procedure, however if this cramping perseveres for more than 24 hours or is not relieved with your normal over the counter pain relief, inform your doctor.
Amniocentesis’ are performed when an abnormality is suspected, and many such pregnancies will unfortunately end in miscarriage even without an amniocentesis.
Other risks include preterm rupture of membranes and infection, but these are very rare.
What must I do and not do after the test?
You should avoid exertion for around 24 hours after the procedure. Preferably your partner, friend or relative should accompany you to drive you home.