Iron and Folic Acid Supplementation in the First Trimester
The premise of this question is incorrect—iron and folic acid supplementation IS recommended during the first trimester and should ideally begin before conception. 1
Folic Acid: Critical First Trimester Timing
Folic acid supplementation must begin at least 4 weeks prior to conception and continue through the first trimester to prevent neural tube defects, which form during the first 28 days of pregnancy when most women don't yet know they're pregnant. 1
Recommended Dosing
- Standard dose: 400 μg (0.4 mg) daily for all women of childbearing age 1
- High-risk dose: 4,000 μg (4 mg) daily starting at least 12 weeks before conception for women with personal/family history of neural tube defects, type 1 diabetes, or high-risk medication exposure, then reduced to 400 μg after 12 weeks gestation 1
Iron Supplementation Throughout Pregnancy
Iron supplementation should begin early in pregnancy, with screening of maternal iron status recommended early in pregnancy to identify women who would benefit most. 1
Physiological Rationale for Early Supplementation
- First trimester iron deficiency matters: While approximately 80% of fetal iron accrues in the last trimester, maternal iron stores must be adequate from early pregnancy to support the entire gestational period 1
- Anemia prevalence increases across trimesters: Iron deficiency ranges from 6.9% in the first trimester to 29.5% in the third trimester, and anemia ranges from 1.8% in the first trimester to 27.4% in the third trimester 1
- Early anemia has worse outcomes: Observational studies suggest an association between adverse infant outcomes and anemia in early pregnancy, but not during the third trimester 1
Evidence for Supplementation Benefits
Daily iron supplementation during pregnancy may reduce maternal anemia (RR 0.30,95% CI 0.20 to 0.47) and iron deficiency at term (RR 0.51,95% CI 0.38 to 0.68), and probably reduces maternal iron-deficiency anemia at term (RR 0.41,95% CI 0.26 to 0.63). 2
Women taking iron supplements are probably less likely to have infants with low birthweight (RR 0.84,95% CI 0.72 to 0.99). 2
Iron + folic acid supplementation probably reduces maternal anemia at term (RR 0.44,95% CI 0.30 to 0.64) and may increase infant birthweight by 57.73 g (95% CI 7.66 to 107.79). 2
Common Misconceptions Addressed
Why Some May Delay Iron Supplementation
The confusion about first trimester supplementation may arise from:
- Side effects: Women receiving daily iron supplementation experience more gastrointestinal side effects (RR 1.29,95% CI 0.83 to 2.02), which can worsen first trimester nausea 2
- Haemoconcentration concerns: Daily iron increases risk of high hemoglobin levels (>130 g/L) during second and third trimesters (RR 0.53,95% CI 0.38 to 0.74), though the clinical significance remains uncertain 3, 2
- Lower iron demands early: The average need of 5.6 mg iron per day is calculated for late pregnancy, not first trimester 1
Clinical Approach
Screen maternal iron status early in pregnancy with hemoglobin and ferritin measurements to identify iron-deficient women who would benefit most from supplementation. 1
- Iron-deficient women (ferritin <15 μg/L): Benefit significantly from supplementation with increased birthweight 1
- Iron-replete women: May not show improved birth outcomes from supplementation, but universal supplementation prevents development of deficiency 1
For women with significant first trimester side effects, intermittent supplementation (2-3 times weekly) produces similar maternal and infant outcomes as daily supplementation but with fewer side effects (RR 0.56,95% CI 0.37 to 0.84). 4
Practical Implementation
- Universal recommendation: All pregnant women should receive iron or iron + folic acid supplementation starting from early pregnancy 1, 2
- Dose: 30 mg elemental iron daily is as effective as higher doses (60-120 mg) with fewer side effects 1
- Timing: Begin folic acid preconceptionally; begin iron supplementation as soon as pregnancy is confirmed or at first antenatal visit 1