When to Start Iron and Folic Acid Supplementation in Pregnancy
Universal Recommendation for All Women of Reproductive Age
All women of childbearing age (12-45 years) who could become pregnant should begin taking 400-800 μg (0.4-0.8 mg) of folic acid daily immediately, regardless of pregnancy plans, because over 50% of pregnancies are unplanned and neural tube closure occurs within the first 28 days after conception—often before pregnancy is recognized. 1, 2
Standard-Risk Women (Low Risk)
Women without specific risk factors should take 400-800 μg (0.4-0.8 mg) of folic acid daily, starting at least 4 weeks (ideally 2-3 months) before planned conception and continuing through the first trimester (12 weeks of pregnancy). 1, 3
After 12 weeks of gestation, continue supplementation at 400-800 μg daily throughout pregnancy and for 4-6 weeks postpartum or as long as breastfeeding continues. 4
This supplementation should be taken in addition to consuming folic acid-fortified foods. 1
High-Risk Women Requiring Higher Doses
Women with any of the following risk factors require 4,000-5,000 μg (4-5 mg) of folic acid daily, starting at least 12 weeks (3 months) before conception:
- Personal history of neural tube defect 1, 2, 5
- Prior pregnancy affected by neural tube defect 1, 5, 4
- First- or second-degree relative with neural tube defect 1, 2
- Male partner with personal history of neural tube defect 4
- Type 1 diabetes mellitus 1
- Exposure to high-risk medications during early pregnancy, including antiepileptic drugs (valproic acid, carbamazepine, lamotrigine) 1, 2
- Prior pregnancy with hydrocephalus 5
Critical Dosing Algorithm for High-Risk Women
Preconception through 12 weeks gestation: 4,000-5,000 μg (4-5 mg) folic acid daily 1, 2, 4
After 12 weeks gestation through delivery: Reduce to 400-1,000 μg (0.4-1.0 mg) daily to decrease potential health consequences of long-term high-dose folic acid ingestion 2, 5, 4
Postpartum: Continue 400-1,000 μg daily for 4-6 weeks or as long as breastfeeding continues 4
Iron Supplementation Timing
Iron supplementation (typically 60 mg elemental iron) should be initiated when folic acid supplementation begins, particularly for women in populations where anemia prevalence exceeds 20%. 6, 7
Daily iron supplementation is more effective than intermittent regimens for preventing anemia at term, though both are acceptable. 7
Important Safety Considerations
Vitamin B12 Screening
Before prescribing folic acid doses exceeding 1 mg daily, vitamin B12 deficiency should be ruled out, as folic acid doses above 0.1 mg may obscure pernicious anemia while neurologic damage progresses. 2, 8
However, vitamin B12 deficiency is uncommon in young women of reproductive age, and investigations are generally not required before initiating supplementation if folic acid is taken in a multivitamin containing 2.6 μg/day of vitamin B12. 2, 4
Dosing Precautions for High-Risk Women
Women requiring more than 1 mg folic acid should take only one multivitamin tablet per day (to avoid excessive intake of other vitamins) and achieve the desired folic acid dose by adding separate folic acid-only tablets. 4
Total daily folic acid intake should not exceed 1,000 μg unless prescribed by a physician for high-risk conditions. 3, 8
Common Pitfalls to Avoid
Starting supplementation after pregnancy recognition is too late—neural tube closure is complete by 28 days post-conception (approximately 6 weeks from last menstrual period), before many women realize they're pregnant. 1, 5
Underestimating risk factors—women taking antiepileptic medications or with family history of neural tube defects in second-degree relatives (such as cousins) require high-dose supplementation, not standard doses. 2
Discontinuing high-dose supplementation too early—high-risk women must continue 4-5 mg daily through the entire first trimester (12 weeks), not just until pregnancy confirmation. 1, 5
Evidence Strength and Limitations
Folic acid supplementation prevents approximately 50-72% of neural tube defect cases, but even with adequate supplementation, some cases cannot be prevented due to multifactorial or monogenic etiology. 2, 5
The 4-5 mg dose recommendation for high-risk women is based on the landmark British MRC Vitamin Study, which demonstrated that high-dose folic acid prevents recurrence of neural tube defects. 5
Side effects (gastrointestinal symptoms) and haemoconcentration (hemoglobin >130 g/L) are more common with daily iron supplementation, though the clinical significance of haemoconcentration remains uncertain. 7