What are the recommended iron and folic acid (folate) supplements for a normal pregnancy?

Iron and Folic Acid Supplementation in Normal Pregnancy

All women capable of becoming pregnant should take 400-800 μg (0.4-0.8 mg) of folic acid daily starting before conception and continuing throughout pregnancy, along with 30 mg of elemental iron daily during pregnancy to prevent maternal anemia and optimize birth outcomes. 1

Folic Acid Supplementation

Standard Dosing for Normal Pregnancy

• Take 400-800 μg (0.4-0.8 mg) of folic acid daily starting at least one month before conception and continuing throughout pregnancy 2, 1
• This dose should be maintained continuously for all women of reproductive age since over 50% of pregnancies are unplanned and neural tube defects develop within the first month after conception, before most women know they are pregnant 2
• Keep total daily folate consumption below 1 mg per day to avoid masking vitamin B12 deficiency, which can lead to irreversible neurologic damage if undiagnosed 2, 1

High-Risk Women Requiring Higher Doses

Women in the following categories need 4-5 mg of folic acid daily during the periconceptional period and first trimester 1:

• Personal or family history of neural tube defects
• Previous pregnancy affected by neural tube defects
• Type 1 diabetes mellitus
• Obesity (BMI > 30 kg/m²) 2
• Exposure to high-risk medications (anticonvulsants) during early pregnancy 1

After 12 weeks gestation, reduce the dose from 4 mg to 400 μg (0.4 mg) daily for high-risk women 1

Critical Timing Considerations

• Folic acid supplementation is most critical during the periconceptional period (at least 1 month before conception through early pregnancy) when neural tube closure occurs 2
• This supplementation can potentially prevent approximately 50% of neural tube defects, though not all cases are preventable due to multifactorial or monogenic etiologies 2, 1

Iron Supplementation

Standard Dosing for Normal Pregnancy

• Take 30 mg of elemental iron daily throughout pregnancy to prevent maternal anemia 2
• This low-dose regimen (30 mg/day) is as effective as higher dose regimens (60-120 mg/day) in preventing iron-deficiency anemia while reducing unwanted gastrointestinal side effects like constipation, nausea, and vomiting 2

Evidence for Iron Supplementation Benefits

Daily iron supplementation during pregnancy provides the following benefits compared to no supplementation:

• Reduces maternal anemia at term (4.0% vs 7.4%) 3
• Reduces iron deficiency at term (44.0% vs 66.0%) 3
• Reduces maternal iron-deficiency anemia at term (5.0% vs 18.4%) 3
• Probably reduces infant low birthweight (5.2% vs 6.1%) 3

Monitoring During Pregnancy

The evidence on routine screening for iron deficiency anemia in asymptomatic pregnant women is insufficient to make a firm recommendation 2. However, when screening is performed:

• Measure serum hemoglobin or hematocrit as the first step 2
• Consider serum ferritin and iron studies including transferrin saturation if anemia is detected 2

Higher Doses for Special Populations

Women after bariatric surgery require 45-60 mg of elemental iron daily (or >18 mg after adjustable gastric banding), with doses adjusted to maintain ferritin within normal limits 2

Combined Iron + Folic Acid Supplementation

A daily multivitamin containing both iron and folic acid is the most practical approach for most pregnant women 1. Combined supplementation:

• Probably reduces maternal anemia at term (12.1% vs 25.5%) compared to no supplementation 3
• May reduce maternal iron deficiency at term (3.6% vs 15%) 3
• Results in infants with higher birthweight (mean difference 57.73 g) 3

Common Pitfalls and Safety Considerations

Avoiding Vitamin B12 Deficiency Masking

• Never exceed 1 mg of folic acid daily without medical supervision, as higher doses can mask vitamin B12 deficiency while allowing neurologic damage to progress 2, 1
• Women should consult healthcare providers about optimal folic acid intake to balance neural tube defect prevention with avoiding excessive consumption 2

Managing Side Effects

• Iron supplementation commonly causes gastrointestinal side effects (nausea, constipation, diarrhea), but these are generally self-limited and transient 2
• Simplified once-daily dosing schedules improve compliance compared to multiple daily doses 2
• Low-dose iron regimens (30 mg/day) reduce side effects while maintaining effectiveness 2

Avoiding Vitamin A Toxicity

• Use beta-carotene (vitamin A precursor) rather than retinol form during pregnancy, as retinol has teratogenicity risk 2
• Exercise caution with multivitamin supplements to prevent excessive vitamin A intake, which can cause birth defects 2

Haemoconcentration Risk

• Daily iron supplementation increases the risk of haemoconcentration (hemoglobin > 130 g/L) during the second and third trimesters, though the clinical significance remains uncertain 4, 3

Practical Implementation

Start supplementation before conception when possible (ideally 3-6 months prior) to optimize nutritional status 2. For women who present already pregnant:

• Begin folic acid and iron supplementation immediately at the standard doses
• Continue throughout pregnancy
• Ensure total daily folic acid remains below 1 mg unless high-risk criteria are met 1