If your first-trimester scan report mentions "NT" or nuchal translucency, here's what that measurement actually is — and what it does and doesn't tell you.
What Nuchal Translucency Is
Every baby has a thin layer of fluid under the skin at the back of the neck between roughly 11 and 14 weeks. Ultrasound can measure its thickness precisely — that measurement is the nuchal translucency (NT).
Why It's Measured
An increased NT is statistically associated with a higher chance of certain chromosomal conditions (such as Down syndrome) and some heart conditions. The NT is combined with your age, blood test markers, and gestational age to calculate a screening risk figure — for example, "1 in 5,000."
The Crucial Point: Screening, Not Diagnosis
This is where most anxiety arises, so let's be clear:
- A normal NT does not guarantee a baby without a chromosomal condition
- An increased NT does not diagnose one — most babies with a mildly raised NT are completely healthy
- The result only adjusts probability, guiding whether you might consider further testing (NIPT blood testing, or diagnostic tests like CVS/amniocentesis)
What Counts as Increased?
Thresholds vary slightly by protocol, but measurements above roughly 3.0–3.5mm generally prompt the offer of specialist review and additional testing — an offer, always your choice.
Timing Matters
NT can only be measured accurately in the 11–14 week window — one more reason not to delay booking your first-trimester scan.
This article is for general information only and is not a substitute for professional medical advice.
Ready to Book Your Ultrasound Scan?
Mascot Healthcare Clinic, Akoka (Yaba), Lagos offers ultrasound scans by appointment only, Monday–Saturday, 9am–5pm. Book online and choose a time that works for you.