Prenatal screening (genetic screening in pregnancy)

Genetic screening, or Prenatal screening, is available to anyone who is pregnant. These tests estimate the chance that your baby has a genetic, chromosomal or physical condition.

There are different types of tests available. They vary in how accurate they are and what information they can give you. No single test checks for all conditions.

Whatever you decide about prenatal testing in your pregnancy, it's important to remember that most babies are born healthy.

Combined first trimester screening

The combined first trimester screening (CFTS) analyses results from a few different tests to calculate the chance of your baby having:

• Down syndrome (trisomy 21)
• Edwards syndrome (trisomy 18)
• Patau syndrome (trisomy 13)

The factors used to measure your baby's chance of having these conditions includes:

• maternal blood test that checks the amounts of different proteins in your blood
• a nuchal translucency (NT) screening ultrasound that measures the thickness of fluid behind your baby's neck
• presence or absence of your baby's nasal bone on ultrasound
• your age and weight
• how far along you are in your pregnancy

You can have this test between 9 weeks and 13 weeks and 6 days of pregnancy.

Second trimester maternal serum screening

Second trimester maternal serum screening calculates the chance of your baby having:

• Down syndrome (trisomy 21)
• Edwards syndrome (trisomy 18)
• neural tube defects (for example, spina bifida)

The factors used to measure your baby's chance of having these conditions includes:

• a blood test
• your age and weight
• pregnancy age

You will usually have this test between 15 and 17 weeks of pregnancy, but you may have it up to 20 weeks of pregnancy.

Non-invasive prenatal test

The non-invasive prenatal test (NIPT) uses a small a sample of your blood. You can have this after 10 weeks of pregnancy. This is because from week 10, some of your baby's DNA from the placenta is found in your blood. The NIPT blood test analyses these DNA fragments.

NIPT estimates the chances your baby may be affected by:

• Down syndrome
• Edwards syndrome
• Patau syndrome
• sex chromosome conditions
• microdeletion syndromes (where a small piece of one of the chromosomes is missing)

NIPT can also identify your baby's sex.

NIPT is the most accurate screening test for detecting Down syndrome.

There are some specialist clinics in Australia that can perform this test. If you would like to have this test, you can ask you antenatal care provider about where you can access NIPT.

The NIPT test is not available under Medicare or your private health fund, so you should ask your provider about out-of-pocket costs before you make an appointment.

If your prenatal screening test shows that your baby has a high chance of a genetic condition, you will be offered genetic counselling. Your counsellor will explain the facts to you, and help you decide what to do next. You may also be offered diagnostic tests such as chorionic villus sampling (CVS) or amniocentesis. These diagnostic tests give you a definitive (yes or no) result.

You do not need to have these tests if you don't want to. You should talk to your healthcare practitioner about your options.

When deciding to have a diagnostic test, there are many things to think about:

• What you would do if the test shows there may be a problem?
• How do you feel about caring for a baby or raising a child with a disability?
• What could it mean for your family?
• How might you feel during your pregnancy?
• Are there circumstances in which you would choose to end the pregnancy?

The cost of prenatal screening depends on a few things, such as:

• whether you are a public or private patient
• the type of test
• whether your doctor thinks your baby has a high chance of having a chromosomal abnormality

You may be able to claim money back from Medicare for part of the cost of the blood test and ultrasound scan.

Medicare doesn't cover the NIPT. This test might cost you a few hundred dollars.

Genetic (prenatal) screening involves screening tests you have during pregnancy to see if your baby may have an increased chance of having a genetic condition.

Carrier screening tests checks if you and your reproductive partner have any changes (mutations) in your genes that increase the chance of your baby having a genetic condition. If you are planning a pregnancy, it is a good idea to consider carrier testing.

Carrier screening is ideally done before pregnancy but can also be done during early pregnancy.

In either case if you are found to have an increased chance of having a child with an inherited genetic condition, you can then choose to have diagnostic testing.

Read more about genetic carrier screening.

Sometimes, the result of your prenatal screening test can be upsetting. Remember that help and support are available to you.

You can find out more about screening tests by asking your doctor, midwife or a genetic counsellor.

• Learn more about genetic screening on The Royal Women's hospital 'Genetic testing in pregnancy' webpage.

• If you are worried or have questions, you can call Pregnancy, Birth and Baby to speak to a maternal child health nurse on 1800 882 436 or video call. Available from 7 am to midnight (AET), 7 days a week (including public holidays).

• PANDA is dedicated to support the mental health and wellbeing of expecting, new and growing families. If you are feeling overwhelmed or need support during your pregnancy, you can reach out to the PANDA helpline at 1300 726 306.
• Read more about shared decision making on the Pregnancy Birth and Baby 'What is shared decision making'.