What is the recommended folic acid (Vitamin B9) dosage for pregnant women?

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Last updated: May 12, 2025View editorial policy

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From the Guidelines

The recommended dosage of folic acid for pregnant women is 400-800 micrograms (0.4-0.8 mg) daily, as recommended by the USPSTF 1. This dosage is recommended for all women planning or capable of pregnancy, and should be taken daily to prevent neural tube defects.

  • The USPSTF recommends that all women planning or capable of pregnancy take a daily supplement containing 0.4 to 0.8 mg (400 to 800 μg) of folic acid, which is a grade A recommendation 1.
  • Women with higher risk factors, such as a personal or family history of neural tube defects, may need a higher dosage of 4 mg daily, as recommended by the American College of Medical Genetics and Genomics 1.
  • Folic acid is crucial during pregnancy because it helps prevent neural tube defects like spina bifida and anencephaly in the developing baby, and also supports the rapid cell growth of the placenta and fetus 1.
  • While folate can be found in foods like leafy greens, beans, and fortified grains, supplements ensure adequate levels during this critical period, especially during the first trimester 1.

From the FDA Drug Label

The usual therapeutic dosage in adults and children (regardless of age) is up to 1 mg daily... and 0.8 mg for pregnant and lactating women, but never less than 0. 1 mg/day. The recommended folic acid dosage for pregnant women is 0.8 mg daily 2.

  • The dosage may need to be adjusted based on individual patient needs and medical conditions.
  • Patients should be kept under close supervision to monitor for any potential relapse or adverse effects.

From the Research

Folic Acid Dosage for Pregnant Women

  • The recommended dosage of folic acid for pregnant women varies depending on the individual's risk factors, with most women recommended to take 400 micrograms (0.4 mg) per day 3, 4, 5.
  • Women who have previously had a pregnancy affected by a neural tube defect are recommended to take a higher dose of 4000 micrograms (4 mg) per day 3, 6.
  • Folic acid supplementation is critical for preventing neural tube defects, and women are advised to start taking it before conception and continue through the first trimester of pregnancy 3, 4, 5.
  • The benefits of folic acid supplementation in preventing neural tube defects are well established, with studies showing a reduction in the frequency of these defects by 25-30% 6.
  • Despite the importance of folic acid supplementation, many women do not receive the recommended daily intake, highlighting the need for increased awareness and education on this topic 3, 7.

Key Findings

  • Folic acid supplementation can prevent 50% or more of neural tube defects, such as spina bifida and anencephaly 3.
  • The first trimester is a critical period for neural tube closure, and decreased blood folic acid levels can inhibit DNA replication and repair, leading to neural tube defects 4.
  • Women who are planning or capable of pregnancy should take a daily supplement containing 0.4 to 0.8 mg (400-800 µg) of folic acid 5.

Recommendations

  • All women capable of becoming pregnant should consume 400 micrograms of folic acid daily to prevent neural tube defects 3, 4, 5.
  • Women at high risk of having a pregnancy affected by a neural tube defect should take 4000 micrograms of folic acid per day 3, 6.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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