Deciding to become a parent has a lot of moving parts but once you have decided that yes, this is for me, it is often closely followed by… now what?

While most women know to take folate supplements, quit smoking, and to set aside that evening glass of wine, there’s one crucial step that often flies under the radar. Genetic carrier testing.

For women who already have children and are trying for another baby, this still applies.

Genetic carrier testing is an optional test that could save you from facing some of the toughest challenges in your journey to parenthood.

In this blog I will talk about being a ‘carrier’. This means that you have one working copy of the gene and one faulty copy. With a pre-pregnant genetic screening or carrier screen, it is testing whether you hold a faulty gene.

There are different tests you may be offered.

Let’s discuss firstly the three-gene panel test. This tests for three genetic conditions Cystic Fibrosis (CF), Spinal Muscular Atrophy (SMA), and Fragile X Syndrome (FXS). Around 5% of people in Australia will carry one of the genes and 1 in 240 couples will both be carriers.

The Conditions: What You Need to Know

Cystic Fibrosis (CF):

• Affects breathing and digestion.
• Lifespan is significantly reduced, with most individuals living into their 30s.
• 1 in 2,500 babies in Australia are born with CF.

Fragile X Syndrome (FXS):

• The most common inherited form of intellectual disability.
• Affects 1 in 3,600 males and 1 in 6,000 females.
• Causes a range of behavioural and physical disabilities.

Spinal Muscular Atrophy (SMA):

• A severe condition affecting muscles, often called “floppy baby syndrome.”
• 1 in 6,000 to 1 in 10,000 babies are born with SMA.
• Severe cases can result in death before the age of two.

These genetic conditions are serious, and many people don’t realise they carry the genes that cause them. This is because being a carrier doesn’t cause symptoms, so most people won’t know they are a carrier unless they are tested. Most carriers are unaware of a family history.

There is also the expanded carrier screen which, depending on the provider you use, can test for mutations that cause more than 400+ recessive conditions.

You may be thinking, the more genes tested the better right? However, due to the sheer number of genes being screened the chances are high (75%!) that you or your partner may have one of the genes.  Deciding whether to test at all or between a simple three-gene panel or extended panel will have a lot to do with how you will process the information, how you ascertain risk and how you plan for future pregnancies.

How is the test performed?

Genetic carrier testing or pre-pregnancy genetic testing for the three-gene panel is a simple blood or saliva test that identifies whether you or your partner carry the genes for CF, SMA, or FXS. For people with eligible for Medicare, the three-gene panel is now bulk billed. For people not eligible for Medicare it costs approximately $350-600 depending on the provider.

Here’s how it works:

1. The woman is usually tested first via a saliva or blood test. This can be done at a pathology collection centre or ordered online.
2. If her results show that she’s not a carrier, the couple can move forward with baby making confidently.
3. If she is a carrier for any condition, her partner is then tested.
4. If both partners are carriers of the gene for the same condition, there’s a significant risk the baby will inherit the disease.

What If Both Partners Are Carriers?

If you are pre-pregnant you may choose to do nothing, have IVF to test embryos, use a donor egg, sperm or embryo or adopt.

For those choosing IVF, this is called pre-implantation genetic diagnosis (PIGD). This involves undergoing an IVF cycle where embryos are tested for the specific genetic condition. Only unaffected embryos are implanted, ensuring the baby will not inherit the genetic condition.

Some people have genetic screening in the first trimester of pregnancy. If a mutated gene is detected, the choices are to continue with the pregnancy, or to have a prenatal diagnostic test such as chorionic villus sampling (CVS) or amniocentesis. If a diagnosis is confirmed, again the choice is to continue with the pregnancy or terminate. These are all big decisions, and you may be advised to see a genetic counsellor and/or psychologist throughout the process.

Timing Is Everything

As specialist Obstetricians, Kate and I see women at about 8 to 10 weeks into pregnancy, rarely do we have couples who’ve done genetic carrier testing beforehand.

Finding out during your pregnancy, at birth or when your baby is not hitting their milestones, comes with heartbreak and difficult decisions.

The best time to get genetic testing is before you start trying to conceive.

This also applies to those who already have healthy children and who haven’t been previously screened, and are trying for a subsequent baby. There is still a chance you are a carrier.

So, if you are planning a pregnancy, the first step is to schedule a visit with your GP to discuss and organise some pre-pregnancy genetic testing.

This GP appointment is also great chance to:

• Review your cervical screening (Pap smear) status.
• Check rubella immunity and update any vaccinations (like chickenpox).
• Discuss folate supplementation and other health considerations.
• Assess irregular cycles or other potential concerns.

(I couldn’t help myself – I also wish everyone knew they should have a pre-pregnancy GP visit too!)

I am passionate about this development during my career. Genetic carrier screening was a technology that not that long ago was costly and inaccessible to most.  Now, due to a lot of hard work by people like Mackenzie’s mission, the three-panel screen is bulk billed for those with an eligible Medicare card. That is great progress.

Written by Obstetrician & Gynaecologist Dr Patrick Moloney