CFTS – Nuchal Translucency Scan

The Combined First Trimester Screen (CFTS) is a test for a chromosomal abnormality performed between 11–13⁺⁶ weeks of pregnancy. The nuchal translucency ultrasound scan is carried out in conjunction with a maternal blood test.

By having the blood test in combination with the nuchal translucency scan (‘combined risk’), approximately 85–90% of babies who have chromosomal abnormalities will be detected.

The CFTS correlates these findings with a likelihood risk to determine if you are at high risk of having a baby with a chromosomal abnormality, such as Downs Syndrome. The CFTS does not directly diagnose an abnormality, but predicts the likelihood of this type of abnormality being present.

All women regardless of age have a small risk of giving birth to a baby with a chromosomal abnormality. The FTS test assesses whether your risk is less than, equal to, or greater than the average risk for your age.

Please make your appointment as soon as you receive the referral from your doctor to ensure you are booked during that period, and ensure enough time to have your blood test.  We recommend patients to book in between 12 and 13 weeks gestation. The fetal gestation age is calculated from the first day of your last menstrual period (LMP) or from an earlier ultrasound-dating scan so please have this information available when you phone South Coast Radiology to make a booking.

The maternal blood test measures two chemicals (PAPP-A and free ß hCG).  These chemicals are produced by the placenta and cross into your bloodstream, and in Downs Syndrome pregnancies the levels of these chemicals in your bloodstream can be abnormal. Please note that a pathology company performs this test, and it needs to be done prior to your nuchal translucency ultrasound, at around 10 weeks gestational age. Please inform pathology staff that you are having a nuchal translucency ultrasound at South Coast Radiology and advise them of the location. The pathology lab will forward your results so these are available at the time of your scan.

You will need to have a full bladder for the ultrasound examination. Empty your bladder one hour prior to the appointment, and then drink 500mls of fluid, finishing 30 minutes before your appointment time. If you know the date of your last period or have had an earlier dating scan, please inform the sonographer when you are taken in for your scan.

A specialist sonographer accredited and licensed by the Fetal Medicine Foundation (FMF) will perform the ultrasound.

First, a non-invasive transabdominal obstetric ultrasound is performed to assess fetal anatomy, where particular care is taken to measure the nuchal translucency. All baby’s retain a small amount of fluid around the head and neck, called the nuchal translucency, at 11–13⁺⁶ weeks’ gestational age. The thickness of the nuchal translucency will be measured, and usually there is an increase in the nuchal translucency when the baby has a chromosomal abnormality.

In approximately 10% of cases a transvaginal (internal) ultrasound scan might be required to gain a more accurate measurement.

Our specialist trained sonographers can also: indicate due date, assess fetal anatomy, detect multiple pregnancy, check fetal position and developing placenta.

There is no specific post-procedural care required, and the patient may resume normal activity straight away.

Our radiologist will interpret the ultrasound images and provide you referring doctor with a comprehensive report. The results of your scan will be sent directly to your referring Doctor, and it is very important you book a timely follow-up appointment to discuss.

Your doctor will still require you to have an 18–20 week morphology ultrasound to assess foetal anatomy and growth, cervix and placental location.

Ultrasound is a safe examination which provides excellent imaging without any known risks. Our staff use ultrasound with care to ensure that patients benefit from what ultrasound offers, with minimum risk. At South Coast Radiology we employ experienced, qualified sonographers accredited with the Australian Sonographer Accreditation Registry, and invest in the latest equipment to ensure patients receive the very best patient care.

CFTS can also give a false high-risk score for a baby that does not have a chromosomal abnormality. This false positive result will occur in approximately 5% of pregnancies tested.

This result only gives an indirect indication of your baby’s likelihood of a chromosomal abnormality. A low-risk score does not mean there is no risk, and a high-risk score does not mean that your baby definitely has a chromosomal abnormality. To acquire a correct diagnosis of a chromosomal abnormality, a direct diagnostic test such as chorionic villus sampling (CVS) or amniocentesis is needed. Your doctor will refer you to an obstetrician who specialises in this field if you require further testing.