A 24-year-old G2P1 at 20 weeks has haemoglobin 9.8 g/dL, MCV 64 fL, MCH 22 pg, RDW 14 percent (normal), and a Mentzer index of 11. Serum ferritin is 35 ng/mL. Her husband has a normal haemogram. What is the MOST appropriate next step?

• A Empirical oral iron for four weeks with repeat haemoglobin
• B Bone marrow aspiration
• C Haemoglobin electrophoresis with quantification of HbA2 ✓
• D Parenteral iron sucrose

Explanation

Microcytosis with a normal RDW, a Mentzer index below 13, and a borderline ferritin point toward beta thalassemia trait rather than pure iron deficiency. HbA2 above 3.5 percent confirms the trait, and this must be established because paternal testing and genetic counselling depend on it. Bone marrow aspiration is obsolete for this diagnosis, and empirical iron risks masking the picture without answering the genetic question.

Reference: Williams Obstetrics, 26th ed.

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Written and medically reviewed by the StethoPrep medical team.