What Does a Color Doppler NT Scan Examine?
Most people are familiar with the Down's syndrome screening, which is recommended to be done between the 12th and 16th weeks of pregnancy. Prior to the Down's syndrome screening, many hospitals also perform a color Doppler NT examination, which belongs to the early screening for Down's syndrome. It is advisable to undergo NT examination between the 11th and 13th weeks of pregnancy. If this period is missed, the NT examination cannot be performed. So, what exactly does the color Doppler NT examination involve? Let's take a closer look.
First, the color Doppler NT examination is used to measure the thickness of the fetal nuchal translucency (NT). NT is the abbreviation for the thickness of the fetal nuchal translucency, which refers to the thickness of the subcutaneous tissue and the transparent band at the back of the fetal neck. The normal value of NT is less than 3mm. At around 11 weeks of gestation, the upper limit of NT value should not exceed 2.2mm. At 13-15 weeks of gestation, the upper limit of NT value should not exceed 2.8mm. If the NT value is found to be greater than or equal to 3mm around 13 weeks of gestation, it is recommended to undergo a chromosomal examination to rule out Down's syndrome. It is important to note that the ruler should be placed on the inner edge of the skin during measurement, and the examination is typically performed around the 13th week of gestation. This time should not be missed. If the pregnant woman is not overweight, a B-ultrasound or color Doppler ultrasound can be used for the examination. However, if the pregnant woman is obese and has a thick abdominal wall, which may affect the clarity of the color Doppler ultrasound observation, a vaginal ultrasound may be used for the examination.
Second, what is the difference between NT and color Doppler ultrasound? In fact, NT is not a frequently required examination item; it is a type of color Doppler ultrasound. However, its focus during the examination is different from that of color Doppler ultrasound. Color Doppler ultrasound is primarily used to observe the fetal development, while NT belongs to early Down's syndrome screening and is typically performed between the 11th and 13th weeks of pregnancy. If this period is missed, the examination cannot be performed. The difference between them is not particularly significant as both are used to assess the presence of chromosomal abnormalities in the fetus. The former examination is mainly used to rule out Down's syndrome, while color Doppler ultrasound is performed multiple times during pregnancy to monitor fetal development.
