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Summary of This Article
Open Neural Tube Defects (ONTDs) are developmental abnormalities of the fetal brain and spinal cord, with spina bifida and anencephaly being the most representative types. These malformations occur because the fetal neural tube does not completely close. Proper diagnosis and management are extremely important for this type of condition.
NIPT (Non-Invasive Prenatal Testing) analyzes cell-free fetal DNA from the mother’s blood to detect chromosomal abnormalities such as Down syndrome, Edwards syndrome, and Patau syndrome. However, NIPT is not designed to detect open neural tube defects (NTDs), which are structural anomalies, not chromosomal ones.
Methods to Diagnose Open Neural Tube Defects
- AFP (Alpha-Fetoprotein) Test:
AFP is a protein produced by the fetal liver. Elevated levels in the mother’s blood or amniotic fluid between 15 and 20 weeks of pregnancy may suggest a neural tube defect. - Ultrasound Examination:
A detailed ultrasound performed between 18 and 22 weeks of gestation can visually detect abnormalities in the brain and spine, such as spina bifida or anencephaly. - Quad Marker Screening:
This test measures four substances (AFP, hCG, estriol, inhibin A) in the mother’s blood to estimate the risk of neural tube defects or chromosomal abnormalities. - Amniocentesis (for confirmation):
If screening results are concerning, a sample of amniotic fluid can be tested to confirm the diagnosis.
Limitations of NIPT
Although highly accurate for chromosomal disorders, NIPT cannot detect structural defects like neural tube abnormalities. A normal NIPT result does not guarantee the absence of NTDs.
Conclusion
AFP testing and detailed ultrasound are the most effective ways to detect open neural tube defects. NIPT should be used specifically for chromosomal screening. Pregnant women should consult with their healthcare provider to choose the most appropriate tests for a safe pregnancy.
