When should you start taking folic acid (Vitamin B9) prior to conception?

Timing of Folic Acid Supplementation Prior to Conception

Women should start taking folic acid at least 1 month before conception, and preferably 3 months before conception, to reduce the risk of neural tube defects. 1

Recommended Timing Based on Risk Status

For Women at Low Risk (general population):

• Start folic acid supplementation at least 1 month before conception 1
• Continue through the first trimester (12 weeks of pregnancy) 1
• Ideally, begin 3 months before conception for optimal protection 2

For Women at High Risk:

• Start folic acid supplementation at least 3 months before conception 1, 2
• High-risk women include those who:
  • Have had a previous pregnancy affected by neural tube defects
  • Have a first-degree relative with a neural tube defect
  • Are themselves affected by a neural tube defect
  • Are taking certain antiseizure medications (e.g., valproic acid, carbamazepine) 1

Dosage Recommendations

Low-Risk Women:

• 400-800 μg (0.4-0.8 mg) of folic acid daily 1
• This can be taken as part of a multivitamin or as a separate supplement

High-Risk Women:

• 4000 μg (4.0 mg) of folic acid daily 1
• This higher dose should be taken until 12 weeks gestation, after which it can be reduced to 400-800 μg (0.4-0.8 mg) daily 1

Rationale for Early Supplementation

The timing of folic acid supplementation is critical because:

• Neural tube closure occurs within the first 28 days after conception 1, 3
• This is often before a woman knows she is pregnant 1
• Approximately 50% of pregnancies in the United States are unplanned 1, 4
• It takes time to build up adequate folate levels in the body to provide protection 3

Common Pitfalls and Caveats

1. Waiting until pregnancy is confirmed: By the time most women confirm pregnancy, neural tube closure has already occurred, making supplementation less effective for preventing neural tube defects.

2. Relying solely on dietary folate: While a folate-rich diet is important, it's difficult to achieve the recommended levels through diet alone, especially since food folates are about half as bioavailable as synthetic folic acid 1.

3. Discontinuing too early: Folic acid should be continued throughout the first trimester (12 weeks), not just until pregnancy is confirmed 1.

4. Exceeding recommended doses without medical supervision: Daily intake should not exceed 1000 μg (1.0 mg) unless prescribed by a physician, due to potential concerns about masking vitamin B12 deficiency 1.

5. Assuming food fortification is sufficient: Despite mandatory fortification of grain products in the United States, studies show that most women still do not achieve optimal folate levels through fortified foods alone 1, 5.

Folic acid supplementation has been shown to reduce the risk of neural tube defects by 40-80% 1, making it one of the most effective preventive interventions available for improving pregnancy outcomes and reducing infant mortality and morbidity.