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Folic acid neural tube prophylaxis and obesity and pregnancy

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

Folic acid supplements at the time of conception helps to prevent neural tube defects. The dose of folic acid recommended for women hoping to conceive is:

  • folic acid 5mg daily
    • to prevent recurrence

    • also dose recommended for women who are:
      • receiving anti-epileptic medication (1) or

      • who have diabetes (2) or

      • who have sickle cell disease (3) or

      • women with a BMI of 30 kg/m2 or greater *(4)

  • folic acid 400 mcg daily to prevent first occurence

* women with a BMI 30 kg/m2 or greater wishing to become pregnant should be advised to take 5 mg folic acid supplementation daily, starting at least 1 month before conception and continuing during the first trimester of pregnancy

Folic acid should be commenced prior to conception and continued for the first trimester.

A review states (5)

  • taking a supplement with 0.4 mg per day (standard dose) of folic acid at least 3 months before pregnancy until the 12th week of pregnancy helps prevent neural tube defects for most individuals
  • guidelines recommend 0.4 mg of folic acid per day in the periconceptional period, and certain guidelines recommend high doses (4-5 mg/day) in women at higher risk for neural tube defects such as those with diabetes, body mass index >= 30, or taking antiepileptic medications or other folate antagonists
    • for those who had a previous pregnancy affected by neural tube defect, high quality evidence from a large randomised clinical trial supports using 4 mg per day of folic acid
    • is a lack evidence to suggest that high doses have additional benefit in preventing neural tube defects in women with other risk factors
  • folic acid supplements should be taken in addition to consuming a folate-rich diet because diet alone does not provide maximal protection against neural tube defects
  • folic acid doses of 4-5 mg per day have not been associated with any side effects or harms, but there is limited evidence on this


  • pregnant women (and those intending to become pregnant) should be informed that dietary supplementation with folic acid, before conception and up to 12 weeks-gestation, reduces the risk of having a baby with neural tube defects (anencephaly, spina bifida). The recommended dose is 400 micrograms per day (1)


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