Can normal NT rule out anencephaly?

summary

NT refers to the transparent layer of the neck, which refers to the thickness of liquid accumulation in the subcutaneous tissue fluid behind the neck of the fetus. It is reflected in the ultrasonic image, which is the maximum thickness of the anechoic layer between the skin behind the neck and the subcutaneous soft tissue measured on the horizontal sagittal section of the cervical spine of the fetus. So let's see if normal nt can rule out anencephaly??

Can normal NT rule out anencephaly?

First: NT measurement is an important part of ultrasound screening in early pregnancy. As a screening, NT examination is an effective imaging method for early detection of fetal abnormalities. In recent 10 years, clinical studies have found that the use of ultrasound to determine the thickness of nuchal translucency has a very important clinical significance. With the increase of its thickness, the possibility of fetal abnormalities also increases. The more obvious NT thickening is, the higher the chance of fetal abnormality is, and the more serious the abnormality is. NT thickening indicates the need for further examination.

Second, thickness can indirectly evaluate the possibility of fetal malformation. When NT exceeds a certain thickness, the higher the chance of fetal abnormality. NT thickening can better evaluate the risk of trisomy 21, trisomy 18 and trisomy 13. If the false positive rate is 5%, more than 75% of Down's syndrome and other severe chromosomal abnormalities can be screened by fetal NT. When the false positive rate is 1%, the detection rate is 60%, which indicates that NT screening is feasible, effective. In addition, it is also associated with fetal congenital cardiac structural abnormalities, which is the most common cause of non chromosomal abnormal NT thickening. And related to other fetal structural abnormalities. Such as skeletal system deformity, diaphragmatic hernia, anterior abdominal wall defect (omphalocele), fetal dyskinesia syndrome can also appear NT thickening. It is also related to spontaneous abortion. It is worth mentioning that the NT value is normal, which does not mean that there is no problem. NT examination is only a marker for indirect diagnosis of fetal abnormalities.

Third: part of the malformation was detected in advance. If the fetus has a large malformation, it will be detected in advance.

matters needing attention

The current research shows that ultrasound prenatal detection is safe, convenient, accurate and easy to follow up. Many international obstetric centers have taken the measurement of nuchal translucency thickness from 11 to 14 weeks of pregnancy as one of the routine examination items.