What causes neural tube defects (NTDs)?

The exact causes of NTDs are not known. Many different factors, including genetics, nutrition, and environmental factors, are known to play a role.

Research shows that getting enough folic acid (also known as folate or vitamin B9) before conception and early in pregnancy can greatly reduce the risk of spina bifida and other NTDs.

In addition, evidence shows that women who are obese, have poorly controlled diabetes, or take certain antiseizure medications, such as phenytoin (Dilantin), carbamazepine (Tegretol), and valproic acid (Depakote), or antifolate (such as aminopterin) are at greater risk than other women are of having an infant with spina bifida or anencephaly.1,3

Some studies suggest that NTDs and miscarriage are more common among fetuses of women who experience high temperatures (such as using a hot tub or sauna or having a fever) during the first 4 to 6 weeks of pregnancy.1,2,3 For this reason, health care providers often advise women who may become pregnant or who are pregnant to avoid using hot tubs or saunas.


  1. Moretti, M. E., Bar-Oz, B., Fried, S., & Koren, G. (2005). Maternal hyperthermia and the risk for neural tube defects in offspring: Systematic review and meta-analysis. Epidemiology, 16(2), 216–219. Retrieved August 6, 2018, from https://journals.lww.com/epidem/fulltext/2005/03000/Maternal_Hyperthermia_and_the_Risk_for_Neural_Tube.10.aspx 
  2. Chescheir, N., & American College of Obstetricians and Gynecologists (ACOG) Committee on Practice Bulletins-Obstetrics. (2003, reaffirmed 2016). ACOG Practice Bulletin: Neural tube defects, Number 44. International Journal of Gynecology and Obstetrics, 83, 123–133.
  3. Centers for Disease Control and Prevention. (2016). Spina bifida. Retrieved February 23, 2017, from http://www.cdc.gov/ncbddd/spinabifida/facts.html
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