Overview

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 trimester, called combined first trimester screening (CFTS), or during the second trimester. You do not need both.

An additional option with CFTS is screening to find out your chance of developing early-onset pre-eclampsia (EO-PE) (a type of high blood pressure).

Cost

The cost of serum screening can vary. Below is a guide:

Test Medicare rebate Approx. out of pocket cost
1st trimester Combined first trimester screening (CFTS) Partial $93
Combined first trimester screening (CFTS) + early onset pre-eclampsia (EO-PE) Partial $112
2nd trimester Maternal serum screening Full rebate for public patients in public antenatal clinics $0
Partial rebate for non-public patients $80
* Prices shown for the blood test only. The cost of the nuchal translucency scan will vary by provider and is not included in this table.
What is this test?

Maternal serum screening is a type of prenatal screening test offered during pregnancy. Screening gives an estimate of the chance that a pregnancy may have a chromosome condition.

There are two serum screening tests available to all women:

  • Combined First Trimester Screening (CFTS)
  • Second Trimester Maternal Serum Screening (2TMSS).

Serum screening gives an estimate of the chance that a pregnancy/baby has a chromosome condition. It does not provide a definite yes or no answer. To confirm results from a screening test, a diagnostic test is needed.

Combined First Trimester Screening (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).

Combined first trimester screening can also provide useful information for the management of a pregnancy, such as your risk of developing early-onset pre-eclampsia.

Second Trimester Maternal Serum Screening (2TMSS)

  • 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 conditions does this test look for?

Maternal serum screening provides an estimate of the chance that a pregnancy has a chromosome condition. Screening during the second trimester can also identify neural tube conditions such as spina bifida.

The conditions that serum screening looks for are:

  • Down syndrome (trisomy 21)
  • Edwards syndrome (trisomy 18)
  • Patau syndrome (trisomy 13) (first trimester only)
  • Neural tube conditions (second trimester only)
  • Early-onset pre-eclampsia (EO-PE optional with first trimester screening only)
    • Pre-eclampsia (PE) is high blood pressure caused by pregnancy. It is one of the most common and life threatening conditions occurring in pregnancy and affects around 1 in 20 pregnant women. Screening as part of CFTS is a simple way to identify the chance of developing early-onset pre-eclampsia (EO-PE). Early detection and treatment can improve pregnancy outcomes.

Maternal serum screening does not identify the sex of the baby.

How do I arrange a test?

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 a VCGS affiliated collection site. If there is no site near you, contact us and we’ll arrange collection.

  • Samples for combined first trimester screening must be collected between 9 weeks +0 days and 13 weeks +6 days gestation. If also screening for EO-PE, collect sample between 11+0 and 13+6 weeks.

  • Early-onset Pre-eclampsia screening is optional when having combined first trimester screening. You must 'opt-in' on the test request form. Screening uses the same blood sample that is used for combined first trimester screening.

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.

Frequently asked questions

Should I have both Combined First Trimester Screening and Second Trimester Maternal Serum Screening?

No. There is no need to have both first and second trimester maternal serum screening.

What’s the difference between maternal serum screening and percept (Non-Invasive Prenatal Testing NIPT)

Both NIPT and maternal serum screening offer high quality screening options to determine if a pregnancy has an increased chance of a chromosome disorder such as Down syndrome. percept (NIPT) is a more accurate screening test than maternal serum screening for the indicated chromosome conditions but it is also more expensive. Maternal serum screening still provides a highly accurate screening test and can provide additional information about the health of the pregnancy, in particular, the risk of early-onset pre-eclampsia.

Because maternal serum screening has a lower cost and is partially covered by Medicare, many women choose to have Combined First Trimester Screening (CFTS) first, then follow up with percept (NIPT) if they get a ‘screen positive’ result.

How accurate is maternal serum screening?

Combined First Trimester Screening (CFTS) will accurately predict 90%, or 9 out of 10 pregnancies affected by Down syndrome.

Second Trimester Maternal Serum Screening (2TMSS) will accurately predict 75-80%, or 8 out of 10 pregnancies affected by Down syndrome.

As with all screening tests, there can be false positive and false negative results. Screening tests are not diagnostic – they are never 100% accurate. Depending on your screening result, diagnostic testing may be offered to confirm the result.

How will I get my results?

Serum screening results will be faxed and delivered electronically (where available) through to your referring doctor.

Combined First Trimester Screening (CFTS) results available 5 days from the time the laboratory receives the ultrasound information. This can be two weeks from when blood was taken.

Second Trimester Maternal Serum Screening (2TMSS) results usually available within one week of having your blood sample taken.

What do my results mean?

Maternal serum screening results are reported as ‘screen negative’ or ‘screen positive’. A result might also be reported as a number, for example, 1 in 300.

Screen negative or low chance: this means it is unlikely your pregnancy is affected by one of the conditions that were being screened for. False negative results can occur and there is no screening test that can rule out all possible conditions. A screen negative result means that diagnostic testing will not usually be offered.

Screen positive or high chance: a screen positive result does not mean a pregnancy is definitely affected by one of the conditions being screened for; it means the pregnancy has an increased chance of having a condition. In most cases, the pregnancy will not be affected.

A diagnostic test is the only way to confirm if a condition is present or to provide reassurance that the pregnancy is not affected. If you receive a screen positive result, you will be offered diagnostic testing.

What happens after a screen positive result?

If you receive a screen positive result, one of the specialist VCGS genetic counsellors will contact your referring doctor to discuss further testing options, such as diagnostic testing. Another option is to have a non-invasive prenatal test (NIPT) like percept™. These options should be discussed with your doctor.

Screening tests do not provide a definitive (yes or no) answer. Diagnostic testing is the only way to confirm the presence of a condition or to reassure a pregnancy is not affected.

I wish to speak to a genetic counsellor about maternal serum screening.

If you have more questions about maternal serum screening please contact one of our genetic counsellors: (03) 9936 6402.

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 phone 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 the receipt of payment to a Medicare centre or online. Once processed, Medicare will send you your rebate.

If you wish to speak with someone about your invoice: Free Call: 1300 557 779.

What does a low PAPP-A (<0.45 MoM) mean?

A low PAPP-A is descriptive of poor early placentation and may result in adverse pregnancy outcomes such as mid trimester miscarriage, fetal growth restriction, intrauterine fetal death, preterm birth or pre-eclampsia. A referral to a specialist O&G service by 20 weeks gestation should be considered to allow for closer maternal and fetal surveillance.