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First Trimester Screening or Nuchal Translucency

(12 week scan)

Nuchal translucency (NT) is the sonographic appearance of a collection of fluid under the skin behind the fetal neck in the first-trimester of pregnancy. It is a non-invasive screening tool to determine how likely your unborn baby will have a chromosomal abnormality, such as Down syndrome.

The test combines the mother’s age related risk, a blood test determining the levels of hormones secreted by the placenta (free βhCG & PAPP-A), the length of the baby from head to bottom (crown to rump length or CRL) and the nuchal translucency measured on ultrasound.


The CRL must be between 45 and 84 mm for the testing to be performed, that is 11 to 13+6 weeks pregnant. The nuchal translucency is a measurement of fluid behind the baby’s neck that is present in all babies during the first trimester of pregnancy.


An increased NT measurement has an association with chromosome abnormalities but can also be associated with structural abnormalities e.g. heart. The fetus can have normal chromosomes even with an increased NT.


The Combined First Trimester Screening test (age + nuchal translucency + bloods) has a 90% accuracy in optimal conditions for predicting your risk for Down Syndrome and some other chromosomal abnormalities.

Our staff are specially trained through the Fetal Medicine Foundation to undertake this examination using a very specific set of guidelines, this ensures consistency an accuracy are maintained. Our staff are registered to take perform NT scans and undertake annual audits.

Advantages to having an NT scan​

There are several advantages to undergoing a 12-week NT scan. As well as giving an estimated individual risk for Down Syndrome and Other Chromosomal abnormalities the NT scan gives us the opportunity to allow early detection of some major abnormalities.


We can assess the general well being of baby, ensure baby is growing appropriately and diagnose multiple fetuses (e.g. twins, triplets). 

How is the NT scan performed?

The nuchal translucency is performed using our state-of-the-art high resolution ultrasound machines. The NT measurement is taken of the fluid filled space at the base of baby's neck as shown in the image below.

The Sonographer will also measure babies length CRL to ensure growth is as expected and undertake a brief anatomy scan although this is limited due to the early gestation of baby.

It is recommended to empty your bladder 1 hour prior to your scan, then drink 2 glasses of water and then do not empty your bladder. You are welcome to bring your family members or a close friend to your scan. 

Usually the scan is able to be completed through the abdomen, occasionally, a transvaginal scan is required to get the images needed to complete the examination. If required transvaginal ultrasounds are optional, performed with discretion and are perfectly safe during pregnancy.

Please ensure you bring your referral form with you to the scan.

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