29/04/2026
12 week NTT fetal ultrasound
At 12 weeks gestational age, the ultrasound NTT scan is a vital screening test that assesses your baby’s early development and helps identify the risk of certain chromosomal conditions. This detailed ultrasound also confirms gestational age, checks the heartbeat, and provides reassurance during a very important stage of pregnancy. Early assessment allows for informed decision-making and appropriate follow‑up care when needed.
Ultrasound NTT (Nuchal Translucency Thickness) Measurement
The NTT measures the thickness of the fluid-filled space at the back of the fetal neck during the 11–13+6 week ultrasound (when crown–rump length is 45–84 mm). It is taken in a strict mid‑sagittal view, with the fetus in a neutral position, and the maximum vertical thickness of the translucency is measured between the skin and the soft tissue overlying the cervical spine.
Normal values (general guidance):
NT increases slightly with gestational age and CRL.
At 11–13+6 weeks, an NT measurement is generally considered within normal limits if it is below the 95th percentile, which is approximately:
~1.2–2.0 mm at 11 weeks
~1.5–2.5 mm at 12 weeks
~2.0–2.8 mm at 13 weeks
An NT of ≥3.0–3.5 mm (depending on guidelines) is typically considered increased and associated with a higher risk of chromosomal conditions or structural anomalies, prompting further assessment.
NTT is a screening tool, not a diagnostic test, and is interpreted together with maternal age and, when applicable, blood markers to estimate overall risk.
For compassionate, professional imaging, contact Julie Rawlins – Diagnostic Ultrasonographer, t/a Inside Image Ultrasound, Hillcrest, Durban, KZN on 031 765 4670.
