Maternal serum screening
What is maternal serum screening?
Maternal serum screening is a blood test used to identify pregnancies with an increased chance of having a chromosome condition, such as Down syndrome.
Serum screening can be done during the first or second trimester. If you have screening in the first trimester, you don't need to have it again in second trimester.
An additional option with first trimester screening is to find out your chance of developing early-onset pre-eclampsia (EO-PE) (a type of high blood pressure).
Note: there is an out-of-pocket cost for most serum screening tests (see below).
How does screening work?
1st trimester
Combined first trimester screening or CFTS
CFTS is performed between 9+0 and 13+6 weeks (ie. 13 weeks and 6 days gestation). If also screening for early-onset pre-eclampsia, your gestation should be between 11+0 and 13+6 weeks).
This test combines a few different measures to give the result.
- Blood to measure two chemicals called PAPP-A and free beta hCG.
- A nuchal translucency ultrasound (NT scan) between 11+0 and 13+6 weeks.
- Your weight, age, IVF details and any relevant medical history
- Presence or absence of the baby’s nasal bone (as seen by ultrasound).
2nd trimester
This is a blood test done between 14+0 and 20+6 weeks gestation (15-17 weeks is best).
Four chemicals are measured:
- alpha-feto protein
- unconjugated estriol
- free beta hCG and
- dimeric inhibin A.
These results are combined with your age, weight and gestation to give a result.
What will screening tell me?
Maternal serum screening gives an estimate of the chance that your pregnancy may have a chromosome condition. Screening during the second trimester can also identify neural tube conditions such as spina bifida.
Serum screening looks for:
- Down syndrome (trisomy 21)
- Edwards syndrome (trisomy 18)
- Patau syndrome (trisomy 13) (first trimester only)
- Early-onset pre-eclampsia (EO-PE optional with first trimester only)
- Neural tube conditions (second trimester only)
Maternal serum screening does not identify the sex of the baby.
How do I arrange screening?
Step 1
Discuss prenatal screening test with your doctor.
Step 2
Your doctor will complete a serum screening test request form.
Step 3
Have your blood collected at an affiliated collection site. If there is no site near you, contact us and we’ll arrange collection.
Step 4
A detailed ultrasound is also required as part of combined first trimester screening. Specialist ultrasonographers are recommended. Your doctor will help organise your ultrasound.
Results
Results will be sent to your health professional approximately 5 days after we receive your ultrasound result. For second trimester screening, results are usually available one week after having your blood collected.
Cost of screening
- Combined first trimester screening = $135 (Invoice from VCGS. Once paid, you can claim $30-40 back from Medicare).
- Combined first trimester screening + early onset pre-eclampsia = $154 (Invoice from VCGS. Once paid, you can claim $30-40 back from Medicare).
- Second trimester screening = free for public patients in a public hospital.