NT normal value
May 22, 2022
Source: Cainiu Health
Dr. Chen Zhe
Introduction
The normal nuchal translucency (NT) value is less than 2.5 mm. This measurement is performed between 11 and 13 weeks of gestation to preliminarily assess the risk of chromosomal abnormalities, including Down syndrome, as increased NT thickness is commonly associated with chromosomal abnormalities. NT screening should be conducted at hospitals with advanced technical capabilities, given the association between chromosomal abnormalities and increased NT thickness.
NT refers to the nuchal translucency thickness—the measurement of the fluid-filled space at the back of the fetal neck. During early pregnancy, metabolic processes within the fetus can lead to the accumulation of a thin, fluid-filled, transparent layer in this region. By measuring the thickness of this layer via ultrasound, clinicians can obtain preliminary insights into potential fetal metabolic abnormalities. So, what constitutes a normal NT value?
Normal NT Value
A normal NT measurement is generally less than 2.6 mm. NT screening is typically performed between 12 and 14 weeks of gestation and helps assess the risk of chromosomal abnormalities—including Down syndrome (trisomy 21). Chromosomal abnormalities are often associated with increased NT thickness. NT assessment requires both high-quality ultrasound equipment and highly skilled sonographers; therefore, it is usually available only at well-equipped hospitals. An NT measurement below 2.6 mm is considered normal, and routine follow-up examinations are recommended. If the NT measurement exceeds 2.6 mm, additional prenatal screening—such as maternal serum screening for Down syndrome—should be performed during the second trimester.
NT measurement is a screening tool used to estimate the risk of Down syndrome in the fetus. It is typically performed between 10 and 14 weeks of gestation, with the optimal timing being at 12 weeks and 5 days. If performed too early, the NT may not be clearly visualized; if performed too late, the subcutaneous fluid may have already been absorbed by the developing lymphatic system.
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