NT examination is one of the items of pregnancy examination. It is a very important test to screen whether the fetal development is abnormal during pregnancy. But many expectant mothers don't know much about NT examination. In fact, NT examination, also known as transparence band scanning, is a method to evaluate whether the fetus has Down's syndrome, with high accuracy. Next, I will introduce what NT check is. Why do pregnant women have NT examination.
What is nt check
NT refers to the "transparent layer of the neck", that is, the maximum thickness between the skin of the horizontal sagittal plane of the fetal cervical spine and the subcutaneous soft tissue. NT examination is also one of the diagnostic bases of Down's screening in the early stage of pregnancy. The purpose of NT examination is to diagnose chromosomal diseases in the early stage of pregnancy and find fetal abnormalities caused by various reasons. The timing of NT examination is very important. If the examination time is more than 14 weeks or less than 11 weeks, the accuracy of the examination will be affected. The appropriate time period of examination is between 11-13 weeks and 6 days of pregnancy, and there is no need to hold urine during the examination.
Why pregnant women do NT
1. Indirect evaluation of fetal malformation
When NT exceeds a certain thickness, the higher the chance of fetal abnormality. It is mainly related to fetal chromosomal abnormalities. NT thickening can better evaluate the risk of fetal suffering from trisomy 21, trisomy 18, trisomy 13, etc. if the false positive rate is 5%, more than 75% of Down's syndrome and other severe chromosomal abnormalities can be screened out through fetal NT. When the false positive rate is 1%, the detection rate is 60%, which indicates that NT screening is feasible and effective .
In addition, it is also related to fetal congenital cardiac structural malformation, the most common cause of non chromosome abnormal NT thickening, and other structural malformations of the fetus. Such as skeletal system deformity, diaphragmatic hernia, defect of anterior abdominal wall (omphalocele), fetal dyskinesia syndrome, NT thickening can also occur. It is also related to spontaneous abortion. Normal NT value does not mean that there is no problem. NT is only a marker for indirect diagnosis of fetal abnormalities.
2. Check whether the fetus is abnormal
NT examination as a screening is an effective imaging method for early detection of fetal abnormalities. In the past 10 years, clinical research has found that it is of great clinical significance to measure the thickness of the nuchal translucency layer with ultrasound. With the increase of its thickness, the possibility of fetal abnormality is also increased. The more obvious NT thickening is, the higher the chance of fetal abnormality is, and the more serious the degree of abnormality is. NT thickening indicates the need for further examination.
3. Determine gestational age
The measurement of fetal biparietal diameter and head hip length in the process of ultrasound examination has good repeatability, which can help obstetricians to determine the gestational age better. After 13 weeks and 6 days of gestation, it is no longer accurate to estimate gestational age by fetal head hip diameter.
reminder:
NT examination is a very important examination during pregnancy. Pregnant women had better do it on time and don't miss the best time. However, before examination, pregnant women had better know more about its purpose and what should be paid attention to before examination. Before NT, pregnant women do not need to have an empty stomach or hold urine. Because it is B ultrasonic examination, so pregnant women had better wear separate clothes, which will be more convenient.
