Diagnostic testing in pregnancy is used to investigate prenatal screening test results, occasions where there is a family history of genetic conditions and to provide assurance that a pregnancy does not carry significant chromosomal changes. Genetic tests can also be used to investigate causes of infertility and recurrent pregnancy loss.
VCGS offers pre and post test genetic counselling and support to all couples and health professionals who use our service.
Genetic testing in the prenatal or pregnancy loss setting is usually offered when:
- there is a family history of a genetic condition.
- a screen positive (or high chance) result has been obtained from prenatal screening tests like Maternal Serum Screening (MSS) or Non-invasive Prenatal Testing (NIPT).
- couples are seeking reassurance.
- there is a history of recurrent pregnancy loss or infertility.
To perform a prenatal diagnostic test, a sample of the placenta or amniotic fluid (fluid surrounding the baby) is required. This sampling is performed by a specialist ultrasonographer.
Recurrent pregnancy loss/infertility investigation is performed on a blood sample from both members of a couple.
Prenatal diagnostic procedures
Chorionic villus sampling (CVS), which is performed between 11-13 weeks. A fine needle is passed through the abdomen to collect cells from the placenta. There is a small risk of miscarriage associated with CVS. This is often reported as 1 in 100, but evidence suggests it could be as low as 1 in 500*.
Amniocentesis, which is available after 15 weeks. A fine needle is passed through the abdomen to collect a sample of amniotic fluid. There is a small risk of miscarriage associated with amniocentesis. This is often reported as 1 in 200, but evidence suggests it could be as low as 1 in 1000*.
*Akolekar. R et al 2015. Procedure-related risk of miscarriage following amniocentesis and
chorionic villus sampling: a systematic review and meta-analysis. Ultrasound Obstet Gynecol, 45:16.
For prenatal diagnostic testing, a chromosome analysis and a Fluorescent insitu Hybridisation or FISH test is performed.
FISH test: FISH provides a rapid result for confirmation or to determine if a pregnancy is affected by chromosome conditions such as Down syndrome, Edwards syndrome or Patau syndrome. Unlike chromosome analysis, FISH only looks at a small number of chromosome changes and results are available within 24-48 hours.
Chromosome analysis: A FISH test will always be followed by confirmatory testing either by a chromosome microarray or a conventional karyotype. These additional tests provide results in 8-14 days and can offer more information than the FISH test.
For the investigation of recurrent pregnancy loss and infertility a conventional chromosome analysis is performed. Results are typically available within 18 days.
Prenatal diagnosis: Unlike prenatal screening tests which only look for genetic changes involving a small number of our chromosomes, prenatal diagnostic investigations using chromosome microarray assess all 23 chromosome pairs. This means diagnostic testing provides a more detailed investigation for chromosomal causes of growth and developmental concerns detected during pregnancy.
Recurrent pregnancy loss and infertility: Chromosome changes can be a common cause of recurrent pregnancy loss or infertility. Conventional chromosome analysis may be offered to couples experiencing recurrent pregnancy loss or infertility to determine if they carry a chromosome change. If a chromosome change is identified there are a number of options available including pre-implantation genetic diagnosis using IVF or prenatal diagnostic testing.
Testing of CVS or amniotic fluid samples is arranged through your doctor. They will organise an appointment with a specialist ultrasonographer, where the a sample is taken under ultrasound guidance. Whether you have a CVS or amniotic fluid sampling will depend on the type of genetic investigation required and your stage of pregnancy.
Investigating genetic causes of recurrent miscarriage or infertility is performed on a blood sample, typically from both members of a couple. This will be arranged by your doctor.
Why have I been offered diagnostic genetic testing?
Prenatal diagnostic testing is usually offered after a screen positive or high chance screening test result; because of an unusual ultrasound finding or because there is a family history of a genetic condition. Couples may also be offered genetic testing if they have been experiencing recurrent pregnancy loss of infertility.
Can diagnostic testing give a false result?
It is very rare for a diagnostic test to give a false result.
For testing on CVS, in some rare cases the cells in the placenta can be genetically different to the cells in the developing baby. This is known as confined placental mosaicism (CPM) and CPM can lead to a false result. Some results obtained on a CVS may require further investigation using amniocentesis.
How and when will I get my results?
Prenatal diagnostics: The preliminary FISH test performed on CVS or amniocentesis provides results in 24-48 hours. The follow up chromosome microarray and/or conventional karyotype can take 10-14 days.
Recurrent pregnancy loss/infertility: Results for chromosome analysis take approximately 18 days.
Results will be available from your referring doctor.
How much does diagnostic testing cost?
The cost for CVS and amniocentesis can vary depending on provider, whether you are a public or private patient and whether or not you are considered to be at a greater chance of having an affected pregnancy. There is a Medicare rebate available to partially cover the cost.
For the laboratory testing, the FISH test costs $175 and there is no Medicare rebate. The chromosome microarray and conventional karyotype are only partially covered by Medicare, so there will be some additional out of pocket costs.
Investigation of recurrent miscarriage or infertility may have an out of pocket cost depending on your circumstances.
Your doctor will be able to advise you about out of pocket expenses.
I’ve received an invoice from VCGS – how do I pay?
After testing is complete, patients will receive an invoice. This can be paid by using BPAY or credit card, or by mail using a money order or cheque. Payment methods are detailed on the invoice.
To claim the Medicare rebate, take your receipt of payment to a Medicare office or online. Once processed, Medicare will send your rebate.
If you wish to speak with someone about your invoice: Free Call: 1300 557 779.