What is an amniocentesis?
This is a procedure that involves taking a small sample of the amniotic fluid from around the baby when testing for chromosome abnormalities like Down syndrome or doing genetic testing in a family with a known genetic disease.
It is done from 15 weeks and by passing a very fine needle through the wall of the womb under ultrasound guidance and taking a small volume of amniotic fluid that surrounds the baby.
The cells that are suspended in the fluid are extracted in a laboratory where they can be processed and examined. It provides a way of doing very accurate testing for chromosomal and genetic problems.
It is associated with a small risk of miscarriage estimated at a 1 in 200-300 chance.
What testing is done on the fluid?
The most common indication for an amniocentesis is testing for chromosomal problems like Down syndrome. The risk of Down syndrome may be considered high when nuchal screening results from the 12 week scan have suggested a high risk, if the mother is older than 35 years or when there is a known chromosomal abnormality in the parents.
Two tests are run on the fluid – one a rapid simple check and the other a longer culture test.
The rapid test looks for simple, common problems that involve an extra or missing major chromosome. This is in fact what causes most forms of Down syndrome. We will phone these results through to you within 2 working days of the amniocentesis. If we are doing the test because of a high risk nuchal result in a baby that looks normally formed then the results of a normal rapid test are extremely reliable.
The culture test allows the scientist to check all the chromosomes more thoroughly and takes bout 2 weeks to report. It allows us to double check the Down’s result and also to look for rarer problems that relate to breakages or rearrangements of chromosomes.
More complex genetic testing on amniotic fluid for familial conditions may need to be sent to laboratories interstate and can take longer. Often we will do this in consultation with genetic specialists from Nepean Hospital and will keep you informed of results as they arrive
On The Day:
Arrange help or time off work on the day of the test.
We need to know your blood group. This is often on your yellow card or in your doctor’s records.
Women with a Rhesus negative blood group need an injection of antiD after the procedure which we arrange for you.
Let our staff know if you take regular aspirin or Clexane as we may need these stopped a few days before the test.
The laboratory will send you a separate bill, a significant amount of which will be refundable by Medicare. The results will be phoned through to you by our doctor.
If you have any concerns Dr Valeria Lanzarone can be contacted at the practice most days on 47212195.