Normal Nuchal Translucency (NT) Thickness in Fetuses

Nuchal translucency (NT) screening measures the thickness of the fluid-filled space at the back of a fetus’s neck to assess the risk of chromosomal abnormalities. An increased NT measurement may indicate fetal structural anomalies, such as Down syndrome.

Normal Nuchal Translucency Thickness

The normal nuchal translucency thickness is generally ≤0.25 cm. A measurement exceeding 0.25 cm raises suspicion for Down syndrome and is also associated with congenital heart disease. The nuchal translucency scan is an early prenatal ultrasound-based screening test used to evaluate the risk of fetal structural anomalies, particularly Down syndrome. If the measured NT value exceeds the normal threshold, it may be associated with fetal karyotypic abnormalities and other structural anomalies; the greater the NT value, the higher the likelihood of structural or chromosomal abnormalities. In addition to chromosomal abnormalities, increased nuchal translucency is also linked to congenital heart disease.

Nuchal translucency (NT) measurement—commonly referred to as the NT scan—is a critical component of prenatal screening. Typically, this ultrasound examination is performed between 11 and 14 weeks of gestation. As it is an ultrasound-based procedure requiring no blood draw, fasting is unnecessary; patients may eat and drink normally before the exam.

If the pregnancy is less than 14 weeks, NT screening is not recommended. Instead, patients should wait until 18–20 weeks for maternal serum screening (e.g., quadruple test) to assess the risk of fetal chromosomal disorders. We hope this information is helpful!