Iron Dosing for Pregnant Women
For routine prophylaxis in pregnant women, prescribe 30 mg of elemental iron daily starting at the first prenatal visit; for treatment of established iron deficiency anemia, prescribe 60-120 mg of elemental iron daily. 1, 2
Prophylactic Dosing (Prevention)
Start all pregnant women on 30 mg elemental iron daily at the first prenatal visit as primary prevention, regardless of initial hemoglobin status 1, 3
The Institute of Medicine recommends a total daily iron requirement of 27 mg during pregnancy, which can be met through prenatal vitamins containing 30-48 mg elemental iron 1, 3
Higher prophylactic doses of 60-100 mg daily may be prescribed for women at increased risk, including:
- Non-Hispanic Black and Mexican American women 1, 3
- Women with short intervals between pregnancies 1, 3
- Vegetarian women (who may require almost twice as much iron due to poor absorption of non-heme iron from plant sources) 1, 3
- Women with gastrointestinal disease or medications that decrease iron absorption 3
Treatment Dosing (Established Anemia)
For confirmed iron deficiency anemia, prescribe 60-120 mg elemental iron daily as first-line therapy 1, 2
This treatment dose should be started immediately upon diagnosis in pregnant women who are not acutely ill, without waiting for additional confirmatory testing 2
Continue treatment throughout pregnancy and reassess after 4 weeks, expecting hemoglobin to increase by at least 1 g/dL or hematocrit by 3% 1, 2
Once hemoglobin normalizes for gestational age, reduce the dose back to 30 mg daily for maintenance 1
Optimizing Absorption and Tolerability
Take iron at bedtime or between meals to maximize absorption and reduce gastrointestinal side effects 2, 4
Avoid concurrent calcium supplements and antacids, which significantly decrease iron absorption; separate these by several hours 2, 3
Counsel patients about iron-rich foods and vitamin C intake to enhance absorption 1, 2
Common side effects include gastrointestinal symptoms, darkening of stool/urine, and tooth staining—these increase with higher doses but are generally minor 1, 3
When Higher Doses Are Not Recommended
Doses above 120 mg daily are not recommended due to increased oxidative stress, impaired absorption of other minerals, and significantly higher rates of gastrointestinal side effects without additional benefit 5, 4, 6
If hemoglobin fails to increase after 4 weeks of 60-120 mg daily despite compliance, evaluate for other causes (thalassemia minor, sickle cell trait) rather than increasing the iron dose 1, 2
Critical Thresholds Requiring Physician Referral
Refer to a physician familiar with anemia in pregnancy if hemoglobin is less than 9.0 g/dL or hematocrit is less than 27.0% for further evaluation 1
If hemoglobin exceeds 15.0 g/dL or hematocrit exceeds 45.0% during second or third trimester, evaluate for poor blood volume expansion and pregnancy complications 1
Postpartum Management
Discontinue iron supplementation at delivery if no risk factors for anemia are present 1, 7
Screen at 4-6 weeks postpartum only if risk factors exist: anemia continued through third trimester, excessive blood loss during delivery, or multiple birth 1, 7
If postpartum anemia is identified, treat with 60-120 mg daily using the same approach as nonpregnant women 1, 7
Common Pitfalls to Avoid
Do not prescribe excessive doses (above 120 mg daily) thinking more is better—this increases side effects without improving outcomes 5, 6
Do not forget to screen at the first prenatal visit—early identification allows for timely intervention 1
Do not continue routine supplementation postpartum in women without risk factors, as this is unnecessary and may cause harm 1, 7