In a 28‑week‑gestation pregnant patient with anemia (hemoglobin 10.9 g/dL, hematocrit 31.6%), when should iron supplementation be started?

Iron Supplementation for Anemia at 28 Weeks Gestation

Your patient should already be on iron supplementation—in fact, she should have been started at her first prenatal visit regardless of her hemoglobin level, and now with a hemoglobin of 10.9 g/dL at 28 weeks, she requires therapeutic-dose oral iron (60-120 mg elemental iron daily) immediately. 1, 2, 3

Universal Prophylaxis vs. Therapeutic Treatment

All Pregnant Women (Regardless of Anemia Status)

• The CDC recommends that all pregnant women begin 30 mg/day of elemental iron at the first prenatal visit, continuing throughout pregnancy and postpartum, regardless of baseline hemoglobin values. 4, 1, 3
• This universal supplementation strategy exists because iron requirements increase threefold during the second and third trimesters to approximately 5.0 mg iron/day, and most women cannot meet this demand through diet alone. 4

Your Patient's Current Status

• At 28 weeks gestation with hemoglobin 10.9 g/dL, your patient meets criteria for anemia in the second/third trimester (defined as Hb <10.5-11.0 g/dL depending on the guideline). 5
• She requires therapeutic dosing, not just prophylactic supplementation. 1, 2

Immediate Management Algorithm

Step 1: Start Therapeutic Iron Now

• Prescribe 60-120 mg elemental iron daily (not the 30 mg prophylactic dose). 1, 2, 3
• ACOG recommends making a presumptive diagnosis of iron deficiency anemia and beginning treatment immediately without waiting for additional testing like ferritin or iron studies in non-acutely ill pregnant women. 1, 2
• Instruct her to take iron between meals to maximize absorption, though taking it with food is acceptable if she cannot tolerate it on an empty stomach (absorption will be reduced but compliance improves). 2, 3

Step 2: Provide Dietary Counseling

• Counsel on consuming iron-rich foods including meat, poultry, certain fruits and vegetables, and iron-fortified grain products. 2
• The CDC specifically recommends dietary counseling as an adjunct to supplementation for pregnant women with anemia. 1

Step 3: Reassess in 4 Weeks

• Recheck hemoglobin or hematocrit after 4 weeks of treatment. 1, 2, 3
• Expected response: hemoglobin increase ≥1 g/dL or hematocrit increase ≥3%. 1, 2, 3

Step 4: If No Response After 4 Weeks

• If there is no adequate response despite confirmed compliance and absence of acute illness, perform additional testing including mean corpuscular volume (MCV), red cell distribution width (RDW), and serum ferritin. 1, 2
• Consider switching to intravenous iron if she fails oral therapy, cannot tolerate oral preparations, or requires rapid correction. 1, 2
• Ferric carboxymaltose is the preferred IV iron option due to rapid effectiveness and better tolerability. 1

Step 5: Once Hemoglobin Normalizes

• Reduce iron dose to 30 mg/day for maintenance once hemoglobin normalizes for gestational age. 1, 3

Critical Thresholds and Red Flags

When to Refer

• If hemoglobin drops below 9.0 g/dL or hematocrit falls below 27%, refer to a physician experienced in pregnancy-related anemia management. 1, 2
• At her current Hb of 10.9 g/dL, she does not yet meet referral criteria but requires close monitoring. 1

Concerning High Values

• If hemoglobin exceeds 15.0 g/dL or hematocrit exceeds 45.0% in the second or third trimester, evaluate for poor blood volume expansion and potential pregnancy complications (not iron overload). 1, 3
• High hemoglobin/hematocrit values are associated with increased risk of fetal growth restriction, preterm delivery, and preeclampsia. 6

Common Pitfalls to Avoid

Compliance Issues

• Verify actual medication adherence—gastrointestinal side effects (constipation, nausea) frequently lead to discontinuation without patients reporting it. 2
• Consider that intermittent dosing (every other day or three times weekly) may be as effective as daily dosing with fewer side effects, though this is not yet standard practice. 5

Timing Misconception

• Do not wait until anemia develops to start iron—the recommendation is universal supplementation from the first prenatal visit. 4, 1, 3
• Your patient at 28 weeks should have already been on 30 mg/day since her first visit; now she needs the higher therapeutic dose. 1, 3

Misinterpreting Third Trimester Anemia

• While anemia in the third trimester may sometimes reflect expanded plasma volume rather than true iron deficiency, this does not change the treatment approach—therapeutic iron is still indicated. 4, 6

Special Considerations

If She Were Vegetarian

• Vegetarian women may require nearly double the standard iron supplementation due to lower absorption of non-heme iron from plant sources. 3

Ethnicity-Based Considerations

• If she is of African, Mediterranean, or Southeast Asian ancestry and fails to respond to adequate oral iron therapy, consider underlying hemoglobinopathies such as thalassemia minor or sickle-cell trait. 1

Safety in Pregnancy

• There is no evidence that oral iron supplementation causes harm to mother or fetus at any gestational age, including the first trimester. 2
• Untreated iron deficiency anemia is associated with adverse outcomes including preterm birth, low birth weight, and postpartum anemia. 4, 5