Receiving a high-risk result from your Combined First Trimester Screening can feel alarming. The moment you see those words on a report, it is easy for your mind to race ahead to the worst possible outcome. But understanding what the result actually means – and what it does not mean – is the most important first step you can take.
This article explains the meaning of a high-risk CFTS result, how that risk is calculated, what the next steps are, and why this result is not a diagnosis.
What Is Combined First Trimester Screening?
Combined First Trimester Screening (CFTS) is a prenatal screening test offered to pregnant women, typically between 11 weeks and 3 days and 13 weeks and 6 days of pregnancy. It combines two components to estimate the statistical likelihood of certain chromosomal conditions in your baby:
- A maternal blood test measuring two hormones – pregnancy-associated plasma protein-A (PAPP-A) and beta human chorionic gonadotropin (beta-hCG)
- An ultrasound that measures the nuchal translucency (NT) – the fluid-filled space at the back of your baby’s neck
These measurements are combined with your age and gestational dating to generate a personalised risk figure. The result is expressed as a ratio, such as 1 in 50 or 1 in 500.
CFTS screens for three chromosomal conditions:
- Trisomy 21 (Down syndrome)
- Trisomy 18 (Edwards syndrome)
- Trisomy 13 (Patau syndrome)
If you are based on the Gold Coast, Combined First Trimester Screening at Haven Ultrasound is performed by accredited sonographers using Fetal Medicine Foundation (FMF) licensed software – the same internationally recognised framework used in leading maternal-fetal medicine centres around the world.
What Does “High Risk” Actually Mean?
The terminology “high risk” is one of the most misunderstood terms in prenatal screening. It does not mean your baby has a chromosomal condition. It means your result falls above a statistical threshold at which further testing is recommended.
In Australia, the standard risk thresholds used are:
- Trisomy 21: a risk greater than 1 in 300 is considered high risk
- Trisomy 18 and 13: a risk greater than 1 in 150 is considered high risk
So if your result comes back as 1 in 150 for trisomy 21, it means that out of 150 pregnancies with the same combination of measurements and age, approximately one baby would be expected to have Down syndrome. That also means approximately 149 would not.
It is worth putting the numbers into perspective. Around 4 to 5 percent of all women who undergo CFTS will receive a high-risk result. Of those, the majority go on to have pregnancies unaffected by chromosomal conditions. The screening is designed to identify the group of pregnancies most likely to benefit from additional investigation – not to deliver a verdict.
Why Did My Result Come Back as High Risk?
Several factors contribute to a high-risk CFTS result, and it is often a combination of findings rather than any single measurement in isolation:
- Increased nuchal translucency (NT) measurement – a thicker NT is associated with a higher risk, though it can also be present in chromosomally normal babies
- Low PAPP-A levels – lower than expected PAPP-A can increase the calculated risk
- Elevated beta-hCG – higher levels of this hormone are associated with trisomy 21 in particular
- Maternal age – the statistical risk of chromosomal conditions increases with age, and this is factored into the final calculation
- Gestational age – the timing of your scan and blood test affects the accuracy of the measurement
No single marker should be interpreted in isolation. The algorithm combines all of these factors together to produce your individual risk figure.
High Risk Does Not Mean Diagnosed
This is perhaps the most critical thing to understand: CFTS is a screening test, not a diagnostic test.
Screening tests estimate probability. Diagnostic tests confirm presence or absence. A high-risk screening result simply means you have moved into the group of pregnancies where further investigation is clinically warranted – it says nothing definitive about your baby’s chromosomes.
The only tests that can confirm a chromosomal diagnosis are invasive diagnostic procedures – chorionic villus sampling (CVS) or amniocentesis – both of which directly analyse fetal chromosomes.
There is also a false-positive rate associated with CFTS. Approximately 5 percent of pregnancies will return a high-risk result even when the baby does not have a chromosomal condition. This is a normal feature of any statistical screening programme and not an error in testing or reporting.
What Are Your Options After a High-Risk CFTS Result?
If your CFTS result is high risk, your doctor or specialist will discuss several pathways with you. The right choice depends on the specific risk figure, your individual circumstances, and your preferences as a parent.
Non-Invasive Prenatal Testing (NIPT)
NIPT is a blood test that analyses cell-free fetal DNA circulating in your bloodstream. It has a significantly higher detection rate for trisomies 21, 18, and 13 than CFTS, and a much lower false-positive rate.
NIPT is typically recommended as a second-line test following a high-risk CFTS result, particularly where the risk figure is in an intermediate range (for example, between 1 in 100 and 1 in 300). A low-risk NIPT result following a high-risk CFTS can provide considerable reassurance, and many women in this situation choose not to proceed to invasive testing once NIPT returns a low-risk finding.
It is important to note that NIPT is still a screening test. It does not provide a definitive chromosomal diagnosis, and a high-risk NIPT result should be confirmed with an invasive diagnostic test before any clinical decisions are made.
Haven Ultrasound offers a pre-NIPT ultrasound scan on the Gold Coast to ensure your NIPT is conducted under the right conditions and that key ultrasound markers are also assessed at the appropriate gestational window.
Chorionic Villus Sampling (CVS)
CVS is an invasive diagnostic test typically performed between 11 and 13 weeks of pregnancy. It involves taking a small sample of placental tissue, which is then analysed in a laboratory to assess fetal chromosomes directly.
CVS is generally recommended when the CFTS risk figure is very high – for example, greater than 1 in 100 – or when a structural anomaly has been identified on ultrasound. Because it is performed in the first trimester, it offers the earliest available diagnostic result.
CVS carries a small risk of pregnancy loss. This risk is generally cited as less than 1 in 100, though it varies between centres and practitioners. Your doctor will discuss the specific risks and benefits with you in the context of your result.
Amniocentesis
Amniocentesis is typically offered from 15 weeks of pregnancy onward. It involves collecting a sample of amniotic fluid, which contains fetal cells that can be chromosomally analysed. Because amniocentesis samples fetal cells rather than placental tissue, it is considered particularly reliable for confirming results where confined placental mosaicism may be a factor.
The risk of pregnancy loss associated with amniocentesis is generally cited as less than 1 in 200. Results can take between a few days and a few weeks depending on the laboratory and the testing method used.
Expectant Management
For some families, particularly those who receive a high-risk result with a ratio at the lower end of the high-risk threshold, choosing not to proceed with further invasive testing is also a valid option. This is a deeply personal decision, and there is no single right answer. Your healthcare team is there to support you through the options, not to make the decision for you.
Understanding the Role of the Nuchal Translucency Scan
The nuchal translucency (NT) measurement is one of the cornerstones of CFTS. It is performed during your first trimester ultrasound and measures the fluid at the back of your baby’s neck.
In chromosomally normal pregnancies, this fluid is typically present in small amounts and resolves naturally as the pregnancy progresses. In pregnancies affected by chromosomal conditions – particularly Down syndrome – the NT measurement tends to be larger than expected.
However, an increased NT does not only indicate chromosomal conditions. It has also been associated with cardiac anomalies and other structural differences in babies who have entirely normal chromosomes. If your NT measurement was elevated, your specialist may recommend a fetal cardiac scan (echocardiogram) in the second trimester regardless of your chromosomal screening result.
The quality and accuracy of the NT measurement depends significantly on the skill and accreditation of the sonographer performing the scan. At Haven Ultrasound, all CFTS scans are performed by sonographers who hold Fetal Medicine Foundation accreditation – a rigorous standard that requires ongoing audit and quality assurance.
When Is NIPT Recommended Over Invasive Testing?
Current Australian clinical guidelines from RANZCOG suggest that invasive diagnostic testing is most strongly recommended when:
- The CFTS risk figure is very high (greater than 1 in 100)
- A fetal structural anomaly has been detected on ultrasound
- Both CFTS and NIPT return elevated results
For risk figures in the intermediate range – between roughly 1 in 100 and 1 in 300 – NIPT is often discussed as an appropriate intermediate step. A low-risk NIPT result in this context may allow many families to avoid invasive testing while still having a high degree of confidence in a chromosomally normal result.
Your doctor or maternal-fetal medicine specialist will guide you through this decision based on the full picture of your clinical findings.
The Emotional Impact of a High-Risk Result
It is entirely normal to feel distressed, frightened, or overwhelmed after receiving a high-risk CFTS result. The waiting period between receiving an initial result and having access to further information is one of the most difficult parts of the process for many families.
Research shows that women who receive a high-risk CFTS result experience significantly elevated anxiety compared to those with low-risk results. This is a recognised and well-documented experience, not a sign of overreaction.
If you find yourself struggling in this period, speaking with your GP, obstetrician, or a genetic counsellor can be genuinely helpful. These professionals are experienced in supporting families through exactly this kind of uncertainty. A genetic counsellor, in particular, can help you interpret your specific risk figures and talk through your testing options in a way that is tailored to your situation.
What Happens if a Chromosomal Condition Is Confirmed?
If further diagnostic testing confirms a chromosomal condition, your healthcare team will work with you to discuss what that means for your pregnancy and your baby. Depending on the specific diagnosis, this may involve:
- Referral to a maternal-fetal medicine (MFM) specialist
- Consultations with paediatric specialists or geneticists
- Ongoing monitoring ultrasounds throughout the pregnancy
- Support services and counselling
It is important to know that a confirmed diagnosis does not determine what path you should take. Families respond in different ways, and healthcare providers are there to support informed decision-making – not to steer you toward any particular outcome.
