Amniocentesis Explained
What is an Amniocentesis ?
This is a simple way of finding out if a baby has a chromosomal disorder. Amniocentesis involves the removal of fluid (liquor) from around the baby under 'direct ultrasound guidance', and it can be performed as early as fourteen weeks. The liquor contains hundreds of living cells that come from the baby's skin.
How is the test done?
The doctor does an ultrasound scan first to check that the baby's size is measured to ensure that you are at the correct dates before doing the test. Following this, the skin is cleansed with an antiseptic sterile wipe, then, a fine sampling needle is passed into the skin of the tummy, which then enters the womb. The doctor knows exactly where to put the needle in because he can see an image on the ultrasound screen. At least 20mls of clear fluid are removed with a syringe. This is then put in a clear plastic container, which is sent to the laboratory for testing.
Does having an Amniocentesis hurt?
Everybody's pain threshold is different. In our experience of performing the test, it would be true to say that most women have only found the test uncomfortable. Some say it is very similar to having an injection or blood removed from the arm.
After the test
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We always advice ladies to take a seat in reception area for a short while before going home. You are advised to take things easy for the next couple of days. You don't have to stay in bed, but do try to avoid household chores or lifting of heavy objects.
When to call the Doctor
Within the next 32-48 hours, you may experience lower abdominal discomfort, similar to period pains, this is not unusual. Paracetmol can be taken to relieve this, and in most cases is effective. If, however your pains become worse, you start to bleed, experience a water type loss or develop a temperature, please contact your GP.
Possible complications
There is a 0.5%-1% chance of a miscarriage happening to you and this is on top of the average risk of miscarriage during pregnancy. Miscarriages which occur within a few days of amniocentesis are probably related to the test. For complications that happen much much later however, it would be difficult to say if these were test related.
Is the test reliable ?
Amniocentesis is 99.9% accurate for diagnosing chromosomal / genetic disorders, but like all tests it has pitfalls. No test is perfect and occasionally the test fails. This occurs in 1% of cases and is due to cells not growing (culture failure), or when the cells grow in a peculiar fashion which gives them more than one result (mosaicism). If this happens, we would let you know and suggest another test.
Results
Results usually take 3-5 weeks because, although the test is very sophisticated, it is still complex.
At the laboratory the cells are separated from the fluid and then placed in a culture dish. The cells are "incubated" and checked every day. At a specific time of development the pattern and number of chromosomes are carefully examined and a diagnosis is made. The process cannot be rushed.
