NT examination, also known as nuchal translucency scan, is a method of evaluating whether a fetus may have Down syndrome by measuring the thickest part of the subcutaneous anechoic translucency layer in the neck of the fetus using ultrasound. This is one of the prenatal examination items for pregnant women. If the NT value detected in the NT examination exceeds the normal range, further screening for abnormalities should be performed, such as amniocentesis or chorionic villi biopsy, to determine whether the patient has Down syndrome or other diseases. So, how to do NT examination for pregnant women?
1. During ultrasound examination, the first step is to measure the fetal head hip length (CRL) and biparietal diameter to determine the gestational age. Then, the fetal structure is examined sequentially, and important indicators such as fetal heart rate, fetal movement, umbilical cord fetal connection site, fetal limb development, intracranial choroid plexus, etc. are observed to detect fetal abnormalities such as anencephaly, choroid plexus cyst, umbilical hernia, and other developmental abnormalities.
2. The thickness of the nuchal translucency is measured on the fetal long axis sagittal plane, with the fetal head aligned with the spine during the measurement. Adjust the magnification to about 3/4 of the screen size occupied by the fetal body. The measurement point is placed on the inner edge of two high echo lines for measurement, which represent skin echoes and soft tissue echoes on the surface of the spine, respectively. The part in between is the transparent zone of the neck.
3. Take a sagittal section of the fetal long axis, with the fetal body in a natural flexed position. Measure the thickest part of the subcutaneous anechoic transparent layer at the neck of the fetus, from the inner edge of the skin layer to the outer edge of the fascia layer, three times, and take the thickest value.
4. If the thickness of the nuchal translucency of the fetus is measured to be ≥ 3mm (or ≥ 2.5mm and the gestational weeks calculated based on the fetal head hip length are
