# Folic acid supplementation before and in early pregnancy

Intervention · id `maternal:folic-acid-supplementation` · Maternal & Newborn Atlas · release `fc5a600ec7387e71` (public)

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Browse, life stage: Preconception; Pregnancy  
Browse, care area: Before pregnancy  

## In plain language

Folic acid is a B vitamin. Taking it every day before and in early pregnancy lowers the chance that a baby is born with a neural tube defect, a serious birth defect of the brain or spine. US guidance advises everyone who is planning a pregnancy, or who could become pregnant, to take a daily supplement containing 0.4 to 0.8 mg (400 to 800 micrograms) of folic acid. MedlinePlus says that getting enough folic acid before and during pregnancy can prevent major birth defects of the baby’s brain or spine.

## Technical summary

USPSTF 2023 reaffirmation: daily 0.4 to 0.8 mg of folic acid, an A recommendation, for persons who are planning to or could become pregnant. The MRC Vitamin Study (1991) is the randomised trial behind the advice for women who had a previous affected pregnancy; its abstract does not give the dose. The USPSTF evidence update found no statistically significant harms for multiple gestation, autism or maternal cancer in the studies it reviewed. These sources do not cover higher-dose advice for people at higher risk.

## Claims, with the population each applies to

## Context: Pregnancies of women with a previous neural tube defect pregnancy (MRC Vitamin Study)

Recipient: Fetal; Population: Fetuses and infants of women at high risk of a pregnancy with a neural tube defect because of a previous affected pregnancy. 1817 women were allocated at random; 1195 had a completed pregnancy in which the fetus or infant was known to have or not have a neural tube defect. The women took the supplement; the outcome is counted in the fetus or infant.; Care setting: 33 centres in seven countries; the abstract does not name the countries or describe the settings.; Geography: Seven countries; the abstract does not name them.; Life stage: Supplementation around the time of conception; outcome at the end of the pregnancy; Gestational age: Not reported; Postnatal age: Not reported; Follow-up: Until a completed pregnancy in which the fetus or infant was known to have or not have a neural tube defect

### In the MRC Vitamin Study, a randomised double-blind trial with a factorial design at 33 centres in seven countries, women at high risk of a pregnancy with a neural tube defect (because of a previous affected pregnancy) were given folic acid, a mixture of seven other vitamins, both, or neither. Of 1195 completed pregnancies in which the fetus or infant was known to have or not have a neural tube defect, 27 had a neural tube defect: 6 in the folic acid groups and 21 in the two other groups. The authors report a 72% protective effect (relative risk 0.28, 95% confidence interval 0.12 to 0.71). The other vitamins showed no significant protective effect (relative risk 0.80, 95% CI 0.32 to 1.72). The abstract reports no demonstrable harm from folic acid, with limited ability to detect rare or slight adverse effects.

- Category: Effect
- Evidence stage: Interventional
- Certainty: Certainty not assessed
- Applies to: Recipient: Fetal; Population: Fetuses and infants of women at high risk of a pregnancy with a neural tube defect because of a previous affected pregnancy. 1817 women were allocated at random; 1195 had a completed pregnancy in which the fetus or infant was known to have or not have a neural tube defect. The women took the supplement; the outcome is counted in the fetus or infant.; Care setting: 33 centres in seven countries; the abstract does not name the countries or describe the settings.; Geography: Seven countries; the abstract does not name them.; Life stage: Supplementation around the time of conception; outcome at the end of the pregnancy; Gestational age: Not reported; Postnatal age: Not reported; Follow-up: Until a completed pregnancy in which the fetus or infant was known to have or not have a neural tube defect
- Limitations: Only the PubMed abstract was read. It does not give the folic acid dose, the numbers of women in each group, or the names of the countries. The counts pool the groups that received folic acid (alone or with other vitamins) against the groups that did not, so per-group denominators are not available and are not computed. The result is for women with a previous affected pregnancy; it does not by itself show the size of the benefit for women without one. 1817 women were allocated at random and 1195 are in the pregnancies the abstract counts.
- Last checked: 2026-10-14
- Sources:
  1. Supports: Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. MRC Vitamin Study Research Group (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, fetched 2026-10-14. The full text and the version of record were not fetched.) <https://pubmed.ncbi.nlm.nih.gov/1677062/>
     Locator: Abstract, sentence 3. Retrieved 2026-10-14T18:18:20Z. Source state: Current. Snapshot hash: 35b6b28be5184c6f9e902c7e02db97769b18f69f757aca52b0fa615917cd5af2.
     How it applies: PubMed abstract of the MRC Vitamin Study report (Lancet 1991).
  2. Supports: Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. MRC Vitamin Study Research Group (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, fetched 2026-10-14. The full text and the version of record were not fetched.) <https://pubmed.ncbi.nlm.nih.gov/1677062/>
     Locator: Abstract, sentence 4. Retrieved 2026-10-14T18:18:20Z. Source state: Current. Snapshot hash: 35b6b28be5184c6f9e902c7e02db97769b18f69f757aca52b0fa615917cd5af2.
     How it applies: PubMed abstract of the MRC Vitamin Study report (Lancet 1991).
  3. Supports: Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. MRC Vitamin Study Research Group (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, fetched 2026-10-14. The full text and the version of record were not fetched.) <https://pubmed.ncbi.nlm.nih.gov/1677062/>
     Locator: Abstract, sentence 5. Retrieved 2026-10-14T18:18:20Z. Source state: Current. Snapshot hash: 35b6b28be5184c6f9e902c7e02db97769b18f69f757aca52b0fa615917cd5af2.
     How it applies: PubMed abstract of the MRC Vitamin Study report (Lancet 1991).
  4. Background: Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. MRC Vitamin Study Research Group (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, fetched 2026-10-14. The full text and the version of record were not fetched.) <https://pubmed.ncbi.nlm.nih.gov/1677062/>
     Locator: Abstract, sentence 1. Retrieved 2026-10-14T18:18:20Z. Source state: Current. Snapshot hash: 35b6b28be5184c6f9e902c7e02db97769b18f69f757aca52b0fa615917cd5af2.
     How it applies: Design, population and the authors’ conclusion.
  5. Background: Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. MRC Vitamin Study Research Group (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, fetched 2026-10-14. The full text and the version of record were not fetched.) <https://pubmed.ncbi.nlm.nih.gov/1677062/>
     Locator: Abstract, sentence 2. Retrieved 2026-10-14T18:18:20Z. Source state: Current. Snapshot hash: 35b6b28be5184c6f9e902c7e02db97769b18f69f757aca52b0fa615917cd5af2.
     How it applies: Design, population and the authors’ conclusion.
  6. Background: Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. MRC Vitamin Study Research Group (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, fetched 2026-10-14. The full text and the version of record were not fetched.) <https://pubmed.ncbi.nlm.nih.gov/1677062/>
     Locator: Abstract, sentence 6. Retrieved 2026-10-14T18:18:20Z. Source state: Current. Snapshot hash: 35b6b28be5184c6f9e902c7e02db97769b18f69f757aca52b0fa615917cd5af2.
     How it applies: Design, population and the authors’ conclusion.

## Context: Pregnant persons and offspring in the studies of the USPSTF 2023 folic acid evidence update

Recipient: Mixed recipients; Population: Pregnant persons and their offspring in the 9 studies of the USPSTF 2023 evidence update that were eligible for harms: 1 randomized trial (n = 431) and 8 observational studies (7 with n = 761 125 and 1 with n = 429 004). The update looked for randomized and nonrandomized cohort studies in very highly developed countries. Harms were reported for multiple gestation, autism spectrum disorder and maternal cancer, so the context covers mothers and offspring and is not split by recipient.; Care setting: Randomized and nonrandomized cohort studies in very highly developed countries (the review inclusion rule); the abstract does not describe settings.; Geography: Very highly developed countries (review inclusion rule); countries are not named in the abstract.; Life stage: Pregnancy-related folic acid exposure and offspring outcomes; Gestational age: Not reported; Postnatal age: Not reported; Follow-up: Not stated in the PubMed abstract

### The evidence update behind the USPSTF 2023 folic acid statement looked for harms of folic acid supplementation around pregnancy. Nine studies were eligible for harms: 1 randomized trial (n = 431) on variations in twin delivery, 7 observational studies (n = 761 125) on autism spectrum disorder and 1 observational study (n = 429 004) on maternal cancer. No study reported statistically significant harms (multiple gestation, autism and maternal cancer) associated with pregnancy-related folic acid exposure.

- Category: Safety
- Evidence stage: Evidence synthesis
- Certainty: Certainty not assessed
- Applies to: Recipient: Mixed recipients; Population: Pregnant persons and their offspring in the 9 studies of the USPSTF 2023 evidence update that were eligible for harms: 1 randomized trial (n = 431) and 8 observational studies (7 with n = 761 125 and 1 with n = 429 004). The update looked for randomized and nonrandomized cohort studies in very highly developed countries. Harms were reported for multiple gestation, autism spectrum disorder and maternal cancer, so the context covers mothers and offspring and is not split by recipient.; Care setting: Randomized and nonrandomized cohort studies in very highly developed countries (the review inclusion rule); the abstract does not describe settings.; Geography: Very highly developed countries (review inclusion rule); countries are not named in the abstract.; Life stage: Pregnancy-related folic acid exposure and offspring outcomes; Gestational age: Not reported; Postnatal age: Not reported; Follow-up: Not stated in the PubMed abstract
- Limitations: Finding no statistically significant harm is not proof that there is none. The abstract gives no effect sizes for the harms. The update searched July 1, 2015 through July 2, 2021 (with surveillance through February 10, 2023), reviewed English-language studies in very highly developed countries, and was a limited update that did not repeat the whole earlier review. Only the PubMed abstract was read.
- Last checked: 2026-10-14
- Sources:
  1. Supports: Folic Acid Supplementation to Prevent Neural Tube Defects: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, fetched 2026-10-14. The full text and the version of record were not fetched.) <https://doi.org/10.1001/jama.2023.9864>
     Locator: Abstract, FINDINGS, sentence 3. Retrieved 2026-10-14T18:18:20Z. Source state: Current. Snapshot hash: 03317be3c7f14cbae88b7c9a5a78b42426113dada5354e4189ed07c527673a57.
     How it applies: PubMed abstract of the USPSTF 2023 evidence update.
  2. Supports: Folic Acid Supplementation to Prevent Neural Tube Defects: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, fetched 2026-10-14. The full text and the version of record were not fetched.) <https://doi.org/10.1001/jama.2023.9864>
     Locator: Abstract, FINDINGS, sentence 7. Retrieved 2026-10-14T18:18:20Z. Source state: Current. Snapshot hash: 03317be3c7f14cbae88b7c9a5a78b42426113dada5354e4189ed07c527673a57.
     How it applies: PubMed abstract of the USPSTF 2023 evidence update.
  3. Supports: Folic Acid Supplementation to Prevent Neural Tube Defects: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, fetched 2026-10-14. The full text and the version of record were not fetched.) <https://doi.org/10.1001/jama.2023.9864>
     Locator: Abstract, CONCLUSIONS AND RELEVANCE, sentence 1. Retrieved 2026-10-14T18:18:20Z. Source state: Current. Snapshot hash: 03317be3c7f14cbae88b7c9a5a78b42426113dada5354e4189ed07c527673a57.
     How it applies: PubMed abstract of the USPSTF 2023 evidence update.
  4. Background: Folic Acid Supplementation to Prevent Neural Tube Defects: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, fetched 2026-10-14. The full text and the version of record were not fetched.) <https://doi.org/10.1001/jama.2023.9864>
     Locator: Abstract, EVIDENCE REVIEW, sentence 1. Retrieved 2026-10-14T18:18:20Z. Source state: Current. Snapshot hash: 03317be3c7f14cbae88b7c9a5a78b42426113dada5354e4189ed07c527673a57.
     How it applies: Search period and inclusion rules of the update.
  5. Background: Folic Acid Supplementation to Prevent Neural Tube Defects: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, fetched 2026-10-14. The full text and the version of record were not fetched.) <https://doi.org/10.1001/jama.2023.9864>
     Locator: Abstract, EVIDENCE REVIEW, sentence 2. Retrieved 2026-10-14T18:18:20Z. Source state: Current. Snapshot hash: 03317be3c7f14cbae88b7c9a5a78b42426113dada5354e4189ed07c527673a57.
     How it applies: Search period and inclusion rules of the update.

## Context: Persons planning to or able to become pregnant (USPSTF 2023 folic acid recommendation)

Recipient: Maternal; Population: Persons who are planning to or could become pregnant. The person takes the supplement; the benefit the USPSTF describes is in their offspring (neural tube defects).; Care setting: Not stated in the PubMed abstract; Geography: United States (statement of the US Preventive Services Task Force); the abstract names no country.; Life stage: Before conception and during pregnancy (persons planning to or who could become pregnant); Gestational age: Not reported; Postnatal age: Not reported; Follow-up: Not applicable (recommendation context)

### The US Preventive Services Task Force (USPSTF) recommends that all persons planning to or who could become pregnant take a daily supplement containing 0.4 to 0.8 mg (400 to 800 micrograms) of folic acid. It grades this an A recommendation. It says it has high certainty that folic acid supplementation has a substantial net benefit in preventing neural tube defects in their offspring. This is a 2023 reaffirmation of an earlier recommendation, made after an evidence update.

- Category: Recommendation
- Evidence stage: Guidance
- Certainty: Certainty not assessed
- Applies to: Recipient: Maternal; Population: Persons who are planning to or could become pregnant. The person takes the supplement; the benefit the USPSTF describes is in their offspring (neural tube defects).; Care setting: Not stated in the PubMed abstract; Geography: United States (statement of the US Preventive Services Task Force); the abstract names no country.; Life stage: Before conception and during pregnancy (persons planning to or who could become pregnant); Gestational age: Not reported; Postnatal age: Not reported; Follow-up: Not applicable (recommendation context)
- Limitations: Only the PubMed abstract was read. It gives the dose, the grade and the task force wording of certainty, but not the evidence behind them. USPSTF certainty levels are the task force’s own wording and not a GRADE rating, so certainty is not assessed here. The abstract does not describe higher-dose advice for people at higher risk of a neural tube defect.
- Last checked: 2026-10-14
- Sources:
  1. Supports: Folic Acid Supplementation to Prevent Neural Tube Defects: US Preventive Services Task Force Reaffirmation Recommendation Statement (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, fetched 2026-10-14. The full text and the version of record were not fetched.) <https://doi.org/10.1001/jama.2023.12876>
     Locator: Abstract, RECOMMENDATION, sentence 1. Retrieved 2026-10-14T18:18:20Z. Source state: Current. Snapshot hash: 8aebb7955183bf45d033ae616f3a133c590a132e130ccfdecbc4810e40114a56.
     How it applies: PubMed abstract of the USPSTF 2023 reaffirmation statement.
  2. Supports: Folic Acid Supplementation to Prevent Neural Tube Defects: US Preventive Services Task Force Reaffirmation Recommendation Statement (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, fetched 2026-10-14. The full text and the version of record were not fetched.) <https://doi.org/10.1001/jama.2023.12876>
     Locator: Abstract, RECOMMENDATION, sentence 2. Retrieved 2026-10-14T18:18:20Z. Source state: Current. Snapshot hash: 8aebb7955183bf45d033ae616f3a133c590a132e130ccfdecbc4810e40114a56.
     How it applies: PubMed abstract of the USPSTF 2023 reaffirmation statement.
  3. Supports: Folic Acid Supplementation to Prevent Neural Tube Defects: US Preventive Services Task Force Reaffirmation Recommendation Statement (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, fetched 2026-10-14. The full text and the version of record were not fetched.) <https://doi.org/10.1001/jama.2023.12876>
     Locator: Abstract, EVIDENCE ASSESSMENT, sentence 1. Retrieved 2026-10-14T18:18:20Z. Source state: Current. Snapshot hash: 8aebb7955183bf45d033ae616f3a133c590a132e130ccfdecbc4810e40114a56.
     How it applies: PubMed abstract of the USPSTF 2023 reaffirmation statement.
  4. Background: Folic Acid Supplementation to Prevent Neural Tube Defects: US Preventive Services Task Force Reaffirmation Recommendation Statement (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, fetched 2026-10-14. The full text and the version of record were not fetched.) <https://doi.org/10.1001/jama.2023.12876>
     Locator: Abstract, POPULATION, sentence 1. Retrieved 2026-10-14T18:18:20Z. Source state: Current. Snapshot hash: 8aebb7955183bf45d033ae616f3a133c590a132e130ccfdecbc4810e40114a56.
     How it applies: Population and the reason for the statement.
  5. Background: Folic Acid Supplementation to Prevent Neural Tube Defects: US Preventive Services Task Force Reaffirmation Recommendation Statement (Publication, edition PubMed record (abstract and bibliographic data) from NCBI E-utilities, fetched 2026-10-14. The full text and the version of record were not fetched.) <https://doi.org/10.1001/jama.2023.12876>
     Locator: Abstract, OBJECTIVE, sentence 1. Retrieved 2026-10-14T18:18:20Z. Source state: Current. Snapshot hash: 8aebb7955183bf45d033ae616f3a133c590a132e130ccfdecbc4810e40114a56.
     How it applies: Population and the reason for the statement.

## Guidance, authorization and access

### Recommendation `maternal:rec-uspstf-2023-folic-acid`

- Intervention: Folic acid supplementation before and in early pregnancy (`maternal:folic-acid-supplementation`)
- Direction: Recommended
- Issued by: U.S. Preventive Services Task Force (`core:uspstf`)
- Guideline record: USPSTF 2023: folic acid supplementation to prevent neural tube defects (reaffirmation) (`maternal:guideline-uspstf-2023-folic-acid`)
- Guideline: Folic Acid Supplementation to Prevent Neural Tube Defects: Preventive Medication (USPSTF final recommendation statement page), edition Final recommendation statement page as fetched on 2026-10-14 (mx-uspstf-folic-acid-for-the-prevention-of-neural-tube-defects-preventive-medication.html). The date under the title is August 01, 2023.; snapshot `maternal:uspstf-folic-acid-2023-2026-10-14`
- Jurisdictions: United States; note: United States (the issuer is a United States task force).
- Strength: A recommendation (USPSTF letter grades: A, B, C and D recommendations, and the I statement for when the evidence is insufficient to recommend for or against. The grade reflects the Task Force's certainty about net benefit. These are not GRADE strength labels.)
- Effective: 2023-08-01 (The date under the title of the USPSTF final recommendation statement page, August 01, 2023. The statement was also published in JAMA, which has its own issue date.)
- Supersession: Not checked
- Applies to: Recipient: Maternal; Population: Persons who are planning to or could become pregnant. The person takes the supplement; the benefit the USPSTF describes is in their offspring (neural tube defects).; Care setting: Not stated in the PubMed abstract; Geography: United States (statement of the US Preventive Services Task Force); the abstract names no country.; Life stage: Before conception and during pregnancy (persons planning to or who could become pregnant); Gestational age: Not reported; Postnatal age: Not reported; Follow-up: Not applicable (recommendation context)
- Basis: claim `maternal:claim-uspstf-2023-folic-acid`

## Connected pages

- Filed under this front: Prevention and nutrition (`maternal:front-prevention-and-nutrition`)
- USPSTF 2023: a daily 0.4 to 0.8 mg supplement (A recommendation) for persons planning to or who could become pregnant: Preconception care (`maternal:preconception-care`) [a claim, not a settled fact; see claim `maternal:claim-uspstf-2023-folic-acid` and its context]
- MRC Vitamin Study: 6 neural tube defects with folic acid versus 21 without, in women with a previous affected pregnancy: Neural tube defects (fetus) (`maternal:neural-tube-defects`) [a claim, not a settled fact; see claim `maternal:claim-mrc-ntd-recurrence` and its context]
- Investigated in: MRC Vitamin Study (1991) (`maternal:mrc-vitamin-study`)

## Provenance

Content hash: 353701bf3e1017d97b2a23b149428c541f975849842fe4c4cad3172a54f48b5d
Last substantive edit: 2026-10-14
Evidence last checked: 2026-10-14