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Normal Values for Nuchal Translucency (NT) on Ultrasound

May 23, 2022 Source: Cainiu Health
Dr. Lv Aiming
Introduction
Fetal nuchal translucency (NT) ultrasound refers to the measurement of the thickness of the fluid-filled space at the back of the fetal neck. The optimal timing for this examination is between 11 weeks and 13 weeks + 6 days of gestation, when the fetal crown-rump length (CRL) measures between 45 mm and 84 mm. A normal NT value is less than 3 mm. Measurement accuracy may vary; therefore, strict adherence to standardized measurement guidelines is essential. Quality control must be performed regarding fetal position, precise measurement location, and the number of measurements taken.

In general, pregnant women around 10 weeks gestation should undergo a color Doppler nuchal translucency (NT) scan. This examination accurately assesses fetal health. So, what is the normal NT measurement on ultrasound?

Normal NT Values on Ultrasound

Fetal NT ultrasound measures the thickness of the nuchal translucency—the fluid-filled space at the back of the fetal neck. The optimal timing for this scan is between 11 weeks and 13 weeks + 6 days of gestation, when the fetal crown-rump length (CRL) measures between 45 mm and 84 mm. A normal NT value is less than 3.0 mm. Measurement accuracy may vary; therefore, strict adherence to standardized measurement guidelines is essential. Quality control must be maintained regarding fetal positioning, precise selection of the measurement point, and the number of measurements performed. If increased nuchal translucency is detected, further detailed ultrasound evaluation—including assessment of nasal bone presence, brain structures, and cardiac anatomy—is recommended. Additionally, invasive prenatal diagnostic testing—such as chorionic villus sampling (CVS) or amniocentesis—for fetal chromosomal analysis should be considered. While some cases of increased NT resolve spontaneously later in pregnancy, others are associated with chromosomal abnormalities. Clinical management—including decisions regarding continuation of pregnancy—should be guided by integrated interpretation of both chromosomal test results and comprehensive ultrasound findings.

Ultrasound imaging has broad clinical applications and can evaluate most major organs and organ systems throughout the body. For example, in the neck region, it can assess the thyroid gland, cervical lymph nodes, carotid arteries, vertebral arteries, and subclavian arteries. In the chest, it can examine the breasts, heart, and subcutaneous masses. Abdominal ultrasound evaluates the liver, gallbladder, pancreas, spleen, and kidneys. Pelvic (lower abdominal) ultrasound assesses the bladder, prostate (in males), uterus, and ovaries.

Ultrasound is also widely used in obstetrics. From early pregnancy through delivery, prenatal ultrasound plays a vital role in monitoring fetal intrauterine growth and screening for structural anomalies. We hope this information is helpful to you. Wishing you good health and happiness!



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