What deformities can NT exclude

NT examination is mainly used to screen for fetal chromosomal abnormalities and some structural abnormalities, such as Down syndrome, trisomy 18 syndrome, trisomy 13 syndrome and other chromosomal diseases, as well as structural abnormalities such as heart malformations, diaphragmatic hernias, and omphalocele. The accuracy of NT examination is affected by factors such as gestational age and measurement techniques, and needs to be comprehensively evaluated in conjunction with subsequent prenatal examinations.

1. Chromosome abnormality screening

NT thickening is closely related to fetal chromosomal abnormalities, especially Down syndrome. When measuring the thickness of the nuchal translucency in fetuses using ultrasound, values exceeding the normal range may indicate an increased risk of chromosomal aneuploidy. This test has a high detection rate for Trisomy 21, but it should be noted that NT value is not a diagnostic criterion and needs to be further confirmed by serological screening or non-invasive DNA.

2. Abnormal cardiac structure

Early NT examination can detect some severe cardiac malformations, such as atrioventricular septal defect, tetralogy of Fallot, etc. The fetal circulatory system has initially formed between 11-14 weeks of pregnancy, and NT thickening may reflect abnormal cardiac load. However, minor cardiac structural issues may need to be diagnosed through subsequent fetal echocardiography.

3. Chest and abdominal deformities

Diaphragmatic hernia and omphalocele and other chest and abdominal wall defects may appear in NT examination. Abnormal development of the diaphragm can cause abdominal organs to enter the chest cavity, while omphalocele manifests as a midline defect in the abdominal wall. These abnormalities are often accompanied by thickening of the NT, but some cases may be missed at a younger gestational age.

4. Skeletal System Abnormalities

Partial lethal bone dysplasia, such as osteogenesis imperfecta, may manifest as NT thickening in the early stages, but most skeletal deformities require subsequent systematic ultrasound observation of long bone development. The screening effect of NT examination on skeletal abnormalities is limited, mainly relying on mid pregnancy ultrasound structural screening.

5. Other structural abnormalities

NT examination may indicate abnormal development of the fetal lymphatic system, such as cervical lymphatic sac tumor. This type of malformation is often associated with chromosomal abnormalities, and simple lymphangiectasia may disappear on its own as gestational age increases. But when merging other abnormalities, the possibility of genetic syndrome should be considered.

NT examination is an important screening method for early pregnancy abnormalities, and it is recommended that all pregnant women complete the test between 11-13 weeks and 6 days of pregnancy. If NT thickening is found, prenatal diagnosis such as chorionic villus sampling and amniocentesis should be performed according to medical advice. Maintain a balanced diet in daily life, supplement folic acid and vitamins in moderation, and avoid exposure to teratogenic substances. Regular prenatal check ups help to dynamically monitor fetal development and intervene promptly in case of abnormalities. Maintaining a positive mindset is equally important for the healthy development of the fetus.