Does NT test require blood draw?

When a woman is 11 to 13 weeks pregnant, she needs to do an NT test, which is mainly used to detect Down syndrome. Down syndrome is a congenital disease that is not hereditary, but it can cause the birth of a child with Down syndrome. The most obvious characteristic of the child is what they eat. Therefore, the best outcome after a child with Down syndrome is to abort it. So, is it necessary to draw blood when doing an NT test?

Does NT test require blood draw?

Does the NT examination require blood drawing? NT screening is performed using color ultrasound and does not require blood drawing. Usually between 11 and 13 weeks of pregnancy, the thickness of the fetal nuchal translucency is measured as a method to assess whether the fetus may have Down syndrome.

1. During ultrasound examination, the crown-rump length (CRL) and biparietal diameter of the fetus are first measured to determine the ultrasound gestational age. Then the fetal structure is checked in sequence, and some important indicators such as fetal heart rate, fetal movement, the connection between the umbilical cord and the fetus, the development of the fetal limbs, and the intracranial choroid plexus are observed to exclude fetal abnormalities such as holoprosencephaly, choroid plexus cysts, umbilical hernias, and other developmental abnormalities.

2. The thickness of the nuchal translucency is measured in the sagittal section of the fetal long axis, with the fetal head and spine in a straight line during measurement. Adjust the magnification so that the fetal body occupies about 3/4 of the screen size. The measurement point is placed at the inner edge of two high-echo lines for measurement. These two high-echo lines represent the skin echo and the soft tissue echo on the spine surface respectively, and the part between them is the nuchal translucency.

3. Take a sagittal section of the fetal long axis, with the fetus in a naturally flexed position, and measure the thickest part of the subcutaneous echo-free transparent layer in the fetal neck, from the inner edge of the skin layer to the outer edge of the fascia layer. Measure three times and take the thickest value.

4. If the thickness of the fetal nuchal translucency is measured to be ≥3mm (or ≥2.5mm and the gestational age calculated based on the fetal crown-rump length is <12 weeks), the pregnant woman is recommended to undergo amniocentesis or chorionic villus sampling for fetal chromosome karyotype analysis.

What is NT test

In our country, doctors generally recommend nuchal translucency scans for people at high risk of Down syndrome, such as pregnant women over 35 years old, those who have given birth to a baby with Down syndrome, or those with a family history of giving birth to a baby with Down syndrome. Although a nuchal translucency scan cannot determine definitively whether the fetus is infected, it can help pregnant women decide whether further diagnostic testing is needed.

NT (nuchal translucency) refers to the maximum thickness between the skin and subcutaneous soft tissue in the sagittal section of the fetal cervical spine. The NT test, also known as the nuchal translucency scan, uses B-ultrasound to measure the thickest part of the subcutaneous echo-free transparent layer in the fetal neck. It is a method used to assess whether the fetus is likely to have Down syndrome and is a screening method. The NT test is different from diagnostic tests such as chorionic villus sampling or amniocentesis. They can provide a definite diagnosis, but the NT test can only indicate the risk. If the NT value of a pregnant woman is detected to be outside the normal range during the NT test, further fetal abnormality screening tests should be performed, such as amniocentesis or chorionic villus sampling, to determine whether she has Down syndrome or other diseases.