Neural tube defects are congenital anomalies that develop in babies while they are in mother’s womb. The exact causes of these defects are not yet known, but some risk factors are thought to be the cause of such defects in fetuses. These risk factors are mentioned below:

  • Folic acid insufficiency
  • Maternal diabetes
  • Obesity
  • Family history
  • Teratogenic medications
  • High heat exposure
  • Gene mutation

Folic acid insufficiency

Folic acid is a vitamin that helps the proper growth of the baby during their life in the mother’s uterus. It is also called vitamin B9. Deficiency of this vitamin during pregnancy increases the chance of neural tube defect in the fetus [1]. What is the mechanism for development of a neural tube defect in the baby of a pregnant lady suffering from deficiency of folic acid? The answer of this question is not properly known. Some information  indicates that  folic acid is helpful in the formation and processing of bony components of vertebra. So, it is necessary to take folic acid before  pregnancy  and during pregnancy in order to save your baby from neural tube defect. Folic acid is present in many foods available naturally, such as, broccoli, some peas and brown rice. Folic acid is also available in the market in the form of tablets. It is estimated  that taking folic acid before conception and during the antenatal period of pregnancy saves seven out of ten cases from  neural tube defects like spina bifida.

Neutral Tube Defects Causes
Figure 1: Prenatal vitamins and Folic acid (Source: www.popsugar.com)

Maternal diabetes mellitus

Maternal diabetes is a risk factor for the baby to develop spina bifida [2]. Gestational diabetes has no effect on  development. Only maternal diabetes is risky for the baby. A high level of glucose in the blood of the mother crosses the placenta and goes to the blood of the fetus  where it decreases the level of folic acid by interacting with  folic acid metabolism. Decreased levels of folic acid is a warning  sign for the development of spina bifida in the fetus. It is very important to control the sugar level of mother  to save baby from developing neural tube defects. For this purpose, insulin is used during pregnancy as it is the drug of choice for high blood sugar levels during pregnancy. It does not produce harmful effects on the baby as it cannot cross the placenta. Other oral hypoglycemic agents are not used during pregnancy because they are dangerous for the baby as they cross the placenta.

Neutral Tube Defects CausesFigure 2: Diabetes is a risk factor for SB (Source: www.anapolschwartz.com)

Obesity

Obesity is a major risk factor for the development of neural tube defects like spina bifida in the fetus [3]. Obesity means the body mass index (BMI) is 30 or more than 30. The mother who is obese  with a BMI more than 40 has three times greater risk of  having  a baby with spina bifida as compared to a  mother whose BMI is 30. How obesity causes neural tube defects is not known but it is important to decrease your BMI  to the normal range to save your baby from the risk of developing neural tube defects. To bring BMI to its normal range, daily exercise is recommended. Further,  diet control is an important factor for the control of BMI.

Family History

A positive family history is an important indicator  for the development of neural tube defects. If a person is present in your family with spina bifida, then the chance of having a baby with spina bifida is increased as compared to the mother who has no positive family history. A mother who delivered a baby with spina bifida has a greater chance to deliver her  next baby with spina bifida as compared to that mother who had normal babies.

Neural tube defects caused by  medications

Some drugs are associated with neural tube defects when used during pregnancy. These drugs are given below:

  • Valproic acid
  • Carbamazepine
  • Lamotrigine

These are anti epileptic drugs that are used to treat the fits of epileptic patients. The percentage of cases treated  with valproic acid is about 1 to 2 percent and the percentage with carbamazepine and lamotrigine is not known exactly. It is recommended that those patients who are taking these drugs should also take contraceptive pills to avoid pregnancy. These drugs interact with the metabolism of folic acid and this causes insufficiency of folic acid in the body. Decreased folic acid level is risk for the development of spina bifida in the fetus. It is advised that a woman  should consult her doctor for  alternative medicines if she wants to be pregnant. Folic acid supplements should also be added in the diet so that deficiency of folic acid does  not occur in the patient due to antiepileptic agents. A woman  should not stop these medicines without the consultation of doctor.

High heat exposure

High heat exposure during pregnancy is also a cause of the development of neural tube defect in the baby [4]. High heat exposure occurs  while a patient suffers from fever or takes a hot water bath. The mechanism behind  high heat exposure causing spina bifida in the baby is not well recognized. What little is known about it is that it enhances the metabolism of body. Folic acid is used up during this increased metabolism causing the insufficiency of folic acid for the development of the fetus thus increasing the risk of development of spina bifida in the fetus. It is advised to take anti-pyretic agents during pregnancy to avoid  heat exposure. Hot water baths should be avoided during pregnancy.

Gene mutation

Gene mutation is also a cause of development of spina bifida in the baby. Many genes are involved in the development of spina bifida and some can be  altered. MTHFR is a gene that is altered causing neural tube defect in the baby. This gene is helpful in the processing of folic acid metabolism. Alteration of this gene causes folic acid deficiency and thus increases the risk of development of spina bifida in the baby.

References

1.     Czeizel AE, Dudas I, Vereczkey A, Banhidy F. Folate Deficiency and Folic Acid Supplementation: The Prevention of Neural-Tube Defects and Congenital Heart Defects. Nutrients 2013;5(11):4760-75.

2.     Anderson JL, Waller DK, Canfield MA, Shaw GM, Watkins ML, Werler MM. Maternal obesity, gestational diabetes, and central nervous system birth defects. Epidemiology 2005;16(1):87-92.

3.     Watkins ML, Scanlon KS, Mulinare J, Khoury MJ. Is maternal obesity a risk factor for anencephaly and spina bifida? Epidemiology 1996;7(5):507-12.

4.     Buckiová D, Kubínová L, Soukup A, Jelínek R, Brown NA. Hyperthermia in the chick embryo: HSP and possible mechanisms of developmental defects. Int J Dev Biol 1998;42(5):737-40.

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Last Modified: December 17, 2014