Neural Tube Defects: Causes and Essential Tests for Expecting Mothers

Neural tube

At 16 weeks of pregnancy, a blood test was conducted to check for gestational diabetes.
During a follow-up visit at 18 weeks, the doctor informed that the incidence of gestational diabetes is low, but there is a potential risk of the fetus having neural tube defects.
A detailed examination is scheduled for 20 weeks.

Could you please explain why neural tube defects might occur? Additionally, what tests should be performed to ensure the fetus is healthy? Thank you for your guidance, and I appreciate your help as an anxious mother.

amy, 30~39 year old female. Ask Date: 2000/11/15

Dr. Li Guanghan reply Obstetrics and Gynecology

Down syndrome screening has a higher rate of neural tube defects, which can generally be assessed via ultrasound around 20 weeks of gestation, with a relatively high detection rate.
The causes of neural tube defects are unknown and are more prevalent in certain populations.
Additionally, amniocentesis followed by quantification of alpha-fetoprotein in the amniotic fluid can also provide insights into the risk.

Reply Date: 2000/11/15

More Info

Neural tube defects (NTDs) are serious congenital malformations that occur when the neural tube, which eventually forms the brain and spinal cord, fails to close completely during early fetal development. This typically happens within the first month of pregnancy, often before a woman even knows she is pregnant. The most common types of NTDs include spina bifida and anencephaly. Understanding the causes and essential tests for expecting mothers is crucial for early detection and management.

Causes of Neural Tube Defects
1. Genetic Factors: Some women may have a genetic predisposition to NTDs, which can be influenced by family history. Certain genetic mutations can affect folate metabolism, increasing the risk of NTDs.

2. Nutritional Deficiencies: One of the most significant risk factors for NTDs is a deficiency in folic acid (vitamin B9). Folic acid is essential for DNA synthesis and repair, and it plays a critical role in the proper closure of the neural tube. Women who do not consume adequate amounts of folic acid before and during early pregnancy are at a higher risk.

3. Environmental Factors: Exposure to certain environmental factors, such as high temperatures (like fever or hot tubs), certain medications (like anti-seizure drugs), and diabetes, can increase the risk of NTDs.

4. Obesity: Maternal obesity has been associated with an increased risk of NTDs, possibly due to metabolic and nutritional factors.

5. Other Medical Conditions: Conditions such as diabetes and epilepsy can also contribute to the risk of NTDs.

Essential Tests for Expecting Mothers
To assess the health of the fetus and check for potential NTDs, several tests can be performed:
1. Ultrasound: A detailed ultrasound, typically performed around 18-20 weeks of gestation, can help visualize the developing fetus and check for physical anomalies, including NTDs. The ultrasound technician will look for signs of proper brain and spinal cord development.

2. Maternal Serum Alpha-Fetoprotein (MSAFP) Test: This blood test measures the level of alpha-fetoprotein (AFP) in the mother’s blood. Elevated levels of AFP can indicate an increased risk of NTDs, prompting further investigation.

3. Amniocentesis: If there are concerns based on ultrasound or AFP levels, amniocentesis may be recommended. This procedure involves taking a sample of amniotic fluid to analyze the fetal DNA for genetic abnormalities and to measure AFP levels directly from the amniotic fluid.

4. Genetic Counseling: If there is a family history of NTDs or other congenital anomalies, genetic counseling may be beneficial. A genetic counselor can provide information on risks and the possibility of genetic testing.

5. Folic Acid Supplementation: While not a test, it is crucial for expecting mothers to take folic acid supplements (typically 400-800 micrograms daily) before conception and during early pregnancy to reduce the risk of NTDs.

Conclusion
If you are concerned about the possibility of neural tube defects, it is essential to maintain open communication with your healthcare provider. They can guide you through the necessary tests and provide support throughout your pregnancy. Early detection and intervention can significantly improve outcomes for both the mother and the baby. Remember, while the risk of NTDs can be concerning, many pregnancies result in healthy babies, especially with proper prenatal care and nutrition.

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