A pregnant woman at 32 weeks has haemoglobin 6.5 g/dL, MCV 64 fL, serum ferritin 4 ng/mL, serum iron 28 mcg/dL. She is intolerant to oral iron. What is the most appropriate intravenous iron preparation to administer, and what is the advantage over older preparations?
- A Iron dextran; can be given as a single total-dose infusion
- B Ferric carboxymaltose; high molecular weight allows single doses of up to 1000 mg with low risk of anaphylaxis ✓
- C Iron sucrose; preferred because it crosses the placenta and supplements fetal stores
- D Ferric derisomaltose; superior because it does not cause hypophosphataemia unlike ferric carboxymaltose
Explanation
Ferric carboxymaltose (FCM) is the preferred IV iron preparation in pregnancy because it allows administration of up to 1000 mg as a single 15-minute infusion, has a low risk of anaphylaxis (due to stable carbohydrate shell that controls iron release slowly), and is effective rapidly. Iron dextran historically had higher anaphylaxis risk. Iron sucrose requires multiple smaller doses (maximum 200 mg per administration). Ferric derisomaltose (Monoferric) also allows 1000 mg infusions but the caveat is that FCM causes hypophosphataemia (via FGF-23 mechanism) in some patients, while derisomaltose does not — option D is technically factual but the question asks for the advantage of the best current first-line choice, which is FCM for its single-dose convenience and safety profile.
Reference: Williams Obstetrics, 26th ed.
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Written and medically reviewed by the StethoPrep medical team.