A 30-year-old woman with iron deficiency anemia in pregnancy has hemoglobin 8.2 g/dL at 28 weeks. She is commenced on oral ferrous sulfate 200 mg three times daily. After 4 weeks, her hemoglobin is 8.9 g/dL — a rise of only 0.7 g/dL. The MOST likely reason for this suboptimal response is:

• A Undiagnosed concurrent folate deficiency causing megaloblastic suppression of erythropoiesis
• B Inadequate treatment duration — significant hemoglobin rise takes 6–8 weeks regardless of dose
• C Poor oral bioavailability due to pregnancy-induced hepcidin elevation blocking intestinal iron absorption
• D Non-compliance or malabsorption — expected hemoglobin rise with adequate absorption is 1–2 g/dL per 3–4 weeks ✓

Explanation

With adequate oral iron absorption, hemoglobin should rise approximately 1–2 g/dL over 3–4 weeks of oral iron therapy in iron deficiency anemia. A rise of only 0.7 g/dL after 4 weeks is suboptimal and most commonly indicates non-compliance (GI side effects from oral iron are common) or malabsorption (H. pylori infection, celiac disease, gastric bypass). Inadequate duration (B) is incorrect — 4 weeks is adequate time to see response. Folate deficiency (A) would cause macrocytosis and megaloblastic changes, not a suboptimal iron response in an otherwise simple iron deficiency scenario. Hepcidin-mediated blockade (C) does occur in inflammatory states but pregnancy itself reduces hepcidin, actually improving absorption — the inflammatory states of infection would cause this, not normal pregnancy.

Reference: Williams Obstetrics, 26th ed.

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Written and medically reviewed by the StethoPrep medical team.