What abnormalities are excluded by NT examination

NT examination is mainly used to screen for fetal chromosomal abnormalities and structural deformities, including Down syndrome, congenital heart disease, spina bifida, abdominal wall defects, limb deformities, etc.

1. Down syndrome

NT examination evaluates the risk of Down syndrome by measuring the thickness of the fetal nuchal translucency and considering factors such as maternal age. Thickening of the nuchal translucency layer is an important ultrasound marker of Down syndrome, and further non-invasive DNA or amniocentesis diagnosis is required when the thickness exceeds the normal range. This examination is of great significance for early screening of Trisomy 21 syndrome.

2. Abnormal NT values in congenital heart disease

are closely related to abnormal fetal cardiac structural development, especially severe congenital heart disease. Thickening of the nuchal translucency may indicate anomalies such as cardiac septal defect and transposition of the great arteries, which require detailed examination by fetal echocardiography during mid pregnancy. Early detection helps evaluate prognosis and develop intervention plans.

3. Spina bifida

NT examination can indirectly indicate the risk of neural tube defects, such as open spina bifida and other deformities. When the NT value is abnormal and the maternal serum alpha fetoprotein is elevated, detailed ultrasound examination of spinal continuity is required. Severe spina bifida may be accompanied by characteristic changes in the brain, such as lemon head sign or banana cerebellum sign.

4. Abdominal wall defects

Abnormal development of the abdominal wall, such as omphalocele and gastroschisis, may be manifested as an increase in NT values. These deformities can cause fetal abdominal contents to protrude from the body surface, and interruption of anterior abdominal wall continuity may be observed during ultrasound examination at 11-13 weeks of pregnancy. Diagnosis should be accompanied by subsequent ultrasound examination to observe the location of internal organs.

5. Limb deformities

Severe limb shortage deformities such as fatal dwarfism may be associated with NT thickening. Early ultrasound can observe the development of fetal long bones, but most limb deformities require detailed evaluation through systematic ultrasound between 18-24 weeks of pregnancy. NT abnormalities combined with limb abnormalities may indicate the presence of chromosomal or genetic syndromes.

NT examination is an important screening method for early pregnancy abnormalities, and it is recommended that all pregnant women complete it between 11-13 weeks and 6 days of pregnancy. No special preparation is required before the examination, but the gestational age needs to be accurately verified. If the results are abnormal, follow the doctor's advice for subsequent diagnostic tests to avoid excessive anxiety. Pay attention to balanced nutrition and folic acid supplementation in daily life, maintain a regular schedule, and create a good environment for the healthy development of the fetus. Regular prenatal check ups help to dynamically monitor fetal development and intervene promptly when problems are detected.