Pearl obstetrics | gynaecology

Screening for Down’s syndrome with PEARL obstetrics | gynaecology

Combined 10 week blood test and 12-14 week ultrasound scan

Until very recently this was the best method of non-invasive testing. 10-15% of Down’s babies are missed unfortunately with this method. Women with high-risk scores then need to undergo amniocentesis (a needle draws off some of the fluid round baby with a small risk of miscarriage) or CVS (a piece of placenta is removed – can be done earlier than amnio but higher risk of miscarriage) to make a diagnosis. The combined test is also used to indicate the possibility of rarer chromosomal problems also. Medicare rebates are available for this testing.

Blood test

This new test, which has just become available, analyses pieces of DNA from baby in the mother’s blood. It’s extremely accurate for Down’s. The chances of a baby with Down’s being missed is very small but because the test is so new, a confirmatory amniocentesis in positive for Down’s cases is still being recommended to be absolutely sure. It is unknown how accurate it is for the other rarer chromosomal abnormalities.

If you want this blood test, the cost is $1350 and it takes 2 weeks to be analysed overseas. There is no Medicare rebate. Consultation fees and rebates also apply.


Done for a variety of reasons, this simple procedure can be performed quickly without issue. The background risk of miscarriage is 1% and amniocentesis adds a little to this risk – but not as much as is generally quoted. Fluid is removed under ultrasound control from the sac away from the baby. This fluid can be analysed immediately, but definitive results take 3 weeks. We expect this procedure to be much less needed over the next few years.


Done earlier than amniocentesis, this procedure uses ultrasound to remove some placental tissue which is then analysed. Results are less reliable than amnio but are returned more quickly. The subsequent miscarriage risk is higher at about 1.5% overall. We expect this procedure to be much less needed over the next few years.

Dr. Mark Sillender. Consultant obstetrician & gynaecologist