Folic Acid Recommendations for Pre-Pregnancy
All women of childbearing age who could become pregnant should take 400 μg (0.4 mg) of folic acid daily, starting at least 4 weeks (ideally 2-3 months) before conception and continuing through the first trimester. 1
Standard Dose for Average-Risk Women
Daily intake of 400 μg (0.4 mg) of folic acid is the cornerstone recommendation from the American College of Medical Genetics and Genomics for all women capable of becoming pregnant. 1
This supplementation should be taken through a combination of supplements, multivitamins, and/or fortified foods, in addition to consuming a healthy, folate-rich diet. 1
Timing is critical: Begin supplementation at least 4 weeks before planned conception, though 2-3 months is preferable, and continue through the first 12 weeks of pregnancy. 1, 2
The U.S. Preventive Services Task Force supports a range of 400-800 μg (0.4-0.8 mg) daily for all reproductive-age women. 1
High-Dose Regimen for High-Risk Women
Women at high risk require 4,000 μg (4 mg) of folic acid daily, starting at least 12 weeks (3 months) before conception and continuing until 12 weeks of gestation, then reducing to 400 μg thereafter. 1
High-risk criteria include:
- Prior pregnancy affected by a neural tube defect (NTD) 1
- Personal history of NTD or first/second-degree relative with NTD 1, 2
- Type 1 diabetes mellitus 1, 3, 2
- Exposure to high-risk medications during early pregnancy (e.g., valproic acid, carbamazepine, methotrexate) 1
- Obesity (BMI > 30 kg/m²) should receive 5 mg daily until 12 weeks of pregnancy 2
Important Clinical Considerations
Vitamin B12 Deficiency Concerns
Total daily folic acid intake should generally not exceed 1,000 μg (1.0 mg) unless prescribed by a physician, due to theoretical concerns about masking vitamin B12 deficiency. 1
However, recent evidence indicates that fortification has not led to a major increase in masking of B12 deficiency. 1
For women taking high-dose folic acid (4-5 mg), concurrent vitamin B12 supplementation (2.6 μg daily) is recommended to mitigate any concerns about masking B12 deficiency. 3, 2
Bioavailability and Food Sources
Synthetic folic acid from supplements is approximately twice as bioavailable as natural folates from food sources. 1
While a folate-rich diet is important, dietary folates alone are insufficient to achieve the protective blood levels needed for NTD prevention. 1
Food fortification (140 μg per 100 grams of enriched grain) has resulted in a 31% decrease in spina bifida and 16% decrease in anencephaly, but is still insufficient for complete protection. 1
Common Pitfalls to Avoid
Starting supplementation too late: Many women don't begin folic acid until after pregnancy is confirmed, missing the critical neural tube closure period (days 21-28 post-conception). 1
Inadequate dosing for high-risk women: Failing to identify high-risk patients who require the 4 mg dose rather than standard 400 μg. 1
Discontinuing supplementation after first trimester: While NTD prevention is the primary focus, continued supplementation throughout pregnancy may reduce homocysteine levels and potentially decrease other pregnancy complications. 4
Limitations of Supplementation
Despite optimal folic acid supplementation compliance, some neural tube defects cannot be prevented because they are of multifactorial or monogenic etiology. 1 This reality underscores the importance of genetic counseling for high-risk women and appropriate prenatal screening regardless of supplementation status. 1