Using ferritin levels to determine iron-deficiency anemia in pregnancy

BACKGROUND: Standard obstetrical practice has included iron therapy for patients with anemia without requiring the determination of iron deficiency. However, the proportion of pregnant women with anemia who have such a deficiency may be relatively modest. We instituted a practice protocol using serum ferritin levels to determine the proportion of women undergoing prenatal care who had both anemia and iron deficiency. METHODS: We evaluated consecutive women entering prenatal care. Those with anemia (hemoglobin level <11 mg/dL) underwent testing for serum ferritin level and other hematologic variables. RESULTS: A total of 182 patients entered prenatal care. Hemoglobin data were available for 173 (95%). Thirty-eight (22%) had anemia (hemoglobin level <11 mg/dL); 1 of those women was excluded from the study. Using a ferritin level of 12 mg per dL as the cutoff for iron deficiency, 54% (20) of the 37 remaining patients with anemia had an iron deficiency, and 46% (17) had anemia not related to such a deficiency. Use of hematologic indices provided on complete blood count were not useful in predicting iron deficiency based on serum ferritin levels. CONCLUSIONS: In our population of prenatal patients with anemia, only approximately half had an iron deficiency. Diagnostic and therapeutic approaches to screening for anemia in pregnancy should be reconsidered and further evaluated.