Prenatal screening tests won’t tell you if your baby has a certain condition; they will only tell you if there is a low or high risk. It’s then up to you if you wish to proceed with a diagnostic test.

Diagnostic tests will give you a more definite result, but carry the risk of complications, such as miscarriage, because they use a needle to collect samples for testing.

While it's your decision, you should always talk to your doctor about the pros and cons of prenatal screening and diagnostic testing.

What are prenatal screening tests?

Prenatal screening tests look for indications that your baby is at risk of having a health condition.

These health conditions include:

• chromosomal conditions (Down syndrome, and Patau syndrome)
• neural tube defects (spina bifida or anencephaly)
• birth defects (congenital heart or kidney conditions)

Screening tests are done with an ultrasound and a blood test. The ultrasound is used to measure the thickness of the fluid behind the baby’s neck and the blood test checks the levels of 2 hormones in the mother’s blood that change during pregnancy.

The results of these 2 tests, along with the mother’s age and weight, and the gestational age of the baby, are used to provide a risk assessment.

Non-invasive prenatal test

A non-invasive prenatal test, or NIPT, is a test that is available in some specialist clinics in Australia. An NIPT is very sensitive to screening for Down syndrome and other chromosomal conditions. However, NIPT is not available under Medicare or your private health fund, so you will have to consider both the cost and availability of the test.

When would I have a prenatal screening test?

Different prenatal screening tests are offered at different stages of your pregnancy, either in the first trimester or second trimester. There are 2 options:

• first trimester screening (9 weeks to 13 weeks and 6 days of pregnancy)
• second trimester screening (14 weeks to 18 weeks of pregnancy)

Many women choose to have the first trimester test, so there is more time to decide what to do if there is a problem. However, some women have screening tests later on - for example, if they were too late for the first trimester test, or if it wasn’t available where they live. You don’t need to have both tests.

Before you have a prenatal screening test, you could discuss with your doctor:

• the advantages and disadvantages of each test
• what further tests might be needed
• what would the result mean for you and your family

What happens after the screening test?

If the test shows your baby is at higher than normal risk of being born with a health condition, you will be offered genetic counselling to explain the facts to you, followed by more tests to properly diagnose the condition. This is called diagnostic testing.

The diagnostic tests available are chronic villus sampling (CVS) and amniocentesis. Both tests involve using an ultrasound to guide a needle into the abdomen of the mother to take a sample from either the placenta or amniotic fluid. CVS is typically done at 11 to 14 weeks and amniocentesis at 15 to 18 weeks.

Both of these tests are invasive and there is a small risk of miscarriage. You do not need to have either of these tests if you don’t want to, but it's important to talk to your doctor about your options.

It’s important to think about what you would do if the test comes back with a positive result. How do you feel about disability? What would it mean for your family? Would you choose to terminate the pregnancy or raise a child with a disability? How would it affect your feelings during your pregnancy?

How much do prenatal screening tests cost?

The cost of prenatal screening depends on whether you are a public or private patient, what sort of test you have, and whether you are considered at high risk for chromosomal abnormalities and other conditions.

You may be able to claim some money back from Medicare to cover part of the cost of the blood test and ultrasound scan. Some tests, such as non-invasive prenatal testing (NIPT), are not covered by Medicare and might cost several hundred dollars.

Where to go for help

If the result of your prenatal screening test is upsetting, it’s important to talk to someone - and help and support are available. You can get more information on prenatal screening tests and what they mean from your doctor, midwife or a genetic counsellor.

Call Pregnancy, Birth and Baby on 1800 882 436 to talk to a maternal child health nurse.