Neural Tube Defects: Causes, Types, Treatment & More

Introduction

The first three months of pregnancy are crucial as it is the time when organ formation takes place. It has been observed that many birth defects happen during the first 3 months of pregnancy. Neural tube defect is one of these defects¹. Neural tube defects are birth defects present in the brain and the spinal cord. Globally, there are more than 3,00,000 newborns every year diagnosed with neural tube defects or 2 per thousand live births². 

Development of the brain and spine begins in the first month of pregnancy. At this stage, the developing brain and spine are called the neural tube. Neural tube defects occur when the tube does not close completely along its length³. Types of neural tube defects include Spinal bifida, Anencephaly, Encephalocele, and Iniencephaly. Spina bifida and anencephaly are more commonly reported in newborns. Foetus detected with iniencephaly and anencephaly die before birth, during the delivery or shortly after birth^4,5.

Signs and Symptoms of Neural Tube Defects

Since neural tube defect occurs in the first month of pregnancy, the mother might not experience any signs and symptoms. During her regular ultrasound, the gynaecologist would possibly reveal signs of this type of birth defect. However, in babies born with neural tube defects, the following general symptoms might be seen⁶:

• Paralysis
• Difficulty in swallowing
•  Seizures
• Urinary and bowel movement problems
• Blindness
• Lack of hearing (partial or complete deafness)
• Cognitive disability
• Lack of alertness

In cases of neural tube defects, normal persistent nerve damage and loss of function are evident at birth³.  So, if your child has a neural tube defect, he/she will probably need admission in NICU and surgery at time of birth.

Prevention is the quintessential when it comes to neural tube defects, and thus the knowledge of risk factors and causes is also very crucial.

Causes of Neural Tube Defects

The exact causes of neural tube defect are still under research, although it is proposed that genetic reasons, nutritional deficiencies, and environmental factors all play a role in causing neural tube defects. Most importantly, the role of folic acid is vital for the healthy development of the foetus, especially in preventing neural tube defects. Just like any other vitamin, vitamin B9 i.e., folic acid levels are extremely crucial during pregnancy. Low levels of folic acid in females before getting pregnant or during the early stages of pregnancy can result in this type of birth defect^3,7.

Risk Factors for Neural Tube Defects

While the exact cause of neural tube defects remains unclear, chances of having them are higher^3,4:

• If the mother has a folic acid deficiency
• If the mother is obese
• If she has uncontrolled diabetes
• If she is on anti-seizure pills or consumes opioids
• If there is any family history of neural tube defects
• If she has chronic unexplained hyperthermia (increased body temperature)

A female who is expecting a child should avoid or reduce the above-mentioned risk factors.

Diagnosis of Neural Tube Defects

Ultrasound testing is done for detecting any abnormalities in the growing foetus. The doctor might require supporting tests to be carried out for coming to a diagnosis. The following tests are a part of the examination during pregnancy:

Noninvasive Test

• Triple screen test/Blood test: Following are the three markers checked during pregnancy to know the status of the pregnancy.
• Alpha-fetoprotein (AFP) is a protein that the foetus makes in the womb. It is quantified during the 15^th to 20^th week of pregnancy. If AFP protein is found to be higher than the normal limit, then the likelihood of developing this defect of the neural tube is also high.
• HCG (human chorionic gonadotropin) hormone is released by the placenta during the 1^st eight weeks of pregnancy. Its levels are found to be normal in neural tube defect cases.
• Estriol is an oestrogen: like hormone released by the foetus and the placenta. Low levels of estriol are helpful in detecting Down’s syndrome^8,9,10,11. 
• The quadruple test (or quad screen): is a prenatal blood test performed between 15 and 20 weeks of pregnancy to screen for potential risks of certain birth defects and chromosomal abnormalities. It measures four specific proteins and hormones in the mother’s blood: alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), unconjugated estriol (uE3), and inhibin-A. The results are used to estimate the risk of conditions like Down syndrome, Edwards syndrome, and open neural tube defects¹². 
• Prenatal ultrasound: Getting an ultrasound done during the 11^th to 14^th week and 18 th to 22nd weeks of pregnancy is required by the doctor to diagnose any type of neural tube defect in the foetus⁹. 

Invasive Test

• Chorionic villous sampling: Chorionic villus sampling (CVS) is a prenatal test performed between 10 and 13 weeks of pregnancy to detect chromosomal and genetic disorders by analysing a sample of placental tissue. During the procedure, a sample of chorionic villi is taken through the abdomen or cervix, and the genetic material is sent to a lab for analysis
• Amniocentesis: Amniotic sac enveloping the foetus and the fluid surrounding the foetus acts as one of the methods to diagnose any birth defects. Using a needle small amount of amniotic sac fluid is withdrawn and studied¹³. This test is conducted during the 15^th to 20^th week of pregnancy.

Treatment of Neural Tube Defects

Amongst the four types of neural tube defects, there is no treatment for infants with anencephaly or iniencephaly. Spina bifida and encephalocele can still be treated through surgical procedures depending upon the severity of the defects¹⁴.

The doctor performs one or more surgeries to align the parts and membrane of the brain back into the skull. Sometimes, more than one surgery is required based on the complications. Frequent doctor or group of doctors’ visits may be required for the rest of their lives depending upon the severity of their condition.

Avoidance of risk factors and prevention is key for such defects.

Prevention of Neural Tube Defects

Neural tube defects can be prevented by lowering the risk factors during the early stages of pregnancy. Taking vitamin B9 supplements as prescribed by the doctor can prevent most neural tube defects⁷.

Complications of Neural Tube Defects

Complications associated with this type of defect are very critical and life-threatening. Following is a list of complications that may arise in an infant who is suffering from neural tube defects:

Complications that can occur in the mother when neural tube defect is diagnosed

• Miscarriage and abortion: A mother might face the complication of spontaneous abortion due to a severe neural tube defect detected in the foetus¹⁵. 

Complications in the baby (can be of 3 types)

A baby is at risk of facing complications at three stages i.e., when it is inside the mother’s womb, when the baby takes birth, and at the infant stage. 

1. Complications in foetus in the womb

• Polyhydramnios: When amniotic fluid accumulates in the amniotic sac due to absence of swallowing activity. Such babies with neural tube abnormalities have learning disabilities because of the restricted growth of brain tissue. About 50% of patients experience the development of polyhydramnios throughout the second and third trimesters¹⁶. 

2. Complications in the newborn baby

• Arnold-Chiari Malformation: It is described as a downward movement of a portion of the brainstem into the foramen magnum as a result of the spinal cord’s improper development¹⁷. 

3. Complications in the infant and later stages of life

• Meningitis: Brain’s fluid continuously oozes out which makes such babies susceptible to infection in the meninges (meninges form a protective layer over the brain)¹⁸. 
• Intellectual disability: The healthy development of the brain depends on the fluid circulating in the brain. Despite having a normal head size, patients with such defects have reduced cortical development and therefore, reduced intellectual abilities¹⁵. 

Conclusion

Neural tube defects or defects of brain and spinal cord in the developing foetus may lead to death of the baby before, during or after birth. Those with spina bifida and encephalocele type of neural tube defect can survive but may have some long-lasting complications depending upon the severity. While the exact cause of these is not clear, majority of neural tube defects can be prevented with supplementation of folic acid during pregnancy. Every woman planning to conceive should consume folic acid daily. A proper consultation with a gynaecologist or any other healthcare provider should be done prior to consuming any medication during pregnancy.

Frequently Asked Questions (FAQs)

References

1. Medline Plus. Birth Defects [Internet]. Medlineplus.gov. National Library of Medicine; 2019. Available from: https://medlineplus.gov/birthdefects.html

2. Fadumo Ahmed Mohamed, Merga Dheresa, Temam Bashir Raru, yusuf N, Tahir Ahmed Hassen, Ame Mehadi, et al. Determinants of neural tube defects among newborns in public referral hospitals in Eastern Ethiopia. BMC Nutrition. 2023 Jul 25;9(1). Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC10369744/

3. MedlinePlus. Neural Tube Defects [Internet]. Medlineplus.gov. National Library of Medicine; 2018. Available from: https://medlineplus.gov/neuraltubedefects.html

4. CDC. Neural Tube Defects [Internet]. Birth Defects. 2024. Available from: https://www.cdc.gov/birth-defects/about/neural-tube-defects.html

5. Chikkannaiah P, Srinivasamurthy V, Satish Prasad BS, Lalyanayak P, Shivaram DN. Iniencephaly: Radiological and pathological features of a series of three cases. Journal of Neurosciences in Rural Practice [Internet]. 2014;5(4):389–93. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4173238/

6. What are the symptoms of neural tube defects? [Internet]. https://www.nichd.nih.gov/. Available from: https://www.nichd.nih.gov/health/topics/ntds/conditioninfo/symptoms

7. Greenberg JA, Bell SJ, Guan Y, Yu Y. Folic Acid Supplementation and Pregnancy: More Than Just Neural Tube Defect Prevention. Reviews in Obstetrics and Gynecology [Internet]. 2011;4(2):52. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC3218540/

8. Alpha-Fetoprotein (AFP) Test: MedlinePlus Lab Test Information [Internet]. Medlineplus.gov. 2017. Available from: https://medlineplus.gov/lab-tests/alpha-fetoprotein-afp-test/

9. How do health care providers diagnose neural tube defects (NTDs)? [Internet]. https://www.nichd.nih.gov/. Available from: https://www.nichd.nih.gov/health/topics/ntds/conditioninfo/diagnosed

10. Reynolds T. The triple test as a screening technique for Down syndrome: reliability and relevance. International Journal of Women’s Health. 2010 May;83. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC2971727/

11. Medline Plus. What is noninvasive prenatal testing (NIPT) and what disorders can it screen for?: MedlinePlus Genetics [Internet]. medlineplus.gov. 2021. Available from: https://medlineplus.gov/genetics/understanding/testing/nipt/

12. Quadruple screen test: MedlinePlus Medical Encyclopedia [Internet]. Medlineplus.gov. 2016. Available from: https://medlineplus.gov/ency/article/007311.htm

13. CDC. Chorionic Villus Sampling and Amniocentesis: Recommendations for Prenatal Counseling [Internet]. CDC. 2019. Available from: https://www.cdc.gov/mmwr/preview/mmwrhtml/00038393.htm

14. What are the treatments for neural tube defects (NTDs)? [Internet]. https://www.nichd.nih.gov/. Available from: https://www.nichd.nih.gov/health/topics/ntds/conditioninfo/treatment

15. Avagliano L, Massa V, George TM, Qureshy S, Bulfamante GP, Finnell RH. Overview on neural tube defects: From development to physical characteristics. Birth Defects Research. 2018 Nov 12;111(19). Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC6511489/

16. Polyhydramnios: MedlinePlus Medical Encyclopedia [Internet]. Medlineplus.gov. 2023. Available from: https://medlineplus.gov/ency/article/003267.htm

17. Chiari Malformation [Internet]. Medlineplus.gov. National Library of Medicine; 2016 [cited 2025 Nov 20]. Available from: https://medlineplus.gov/chiarimalformation.html

18. Frezer Mengiste, Mulugeta Sitot Shibeshi, Dagnachew Gechera. Neural Tube Defect in a Resource Limited Setting: Clinical Profile and Short Term Outcome. Pediatric Health, Medicine and Therapeutics [Internet]. 2023 Sep 1 [cited 2024 Jan 22];Volume 14:289–99. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10517686/

19. Flores A, C Vellozzi, Valencia D, Sniezek J. Global Burden of Neural Tube Defects, Risk Factors, and Prevention. Indian journal of community health [Internet]. 2014 Nov;26(Suppl 1):3. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC4480200/

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