Prevalence of Iron Deficiency and Anemia in Pregnancy in a Canadian Cohort and Definition of Normal Hemoglobin Ranges in Iron-Replete Women.

OBJECTIVES

The objectives were to identify the prevalence of iron deficiency and anemia in pregnancy and define the normal hemoglobin range in iron-replete women. Secondary outcomes included defining hemoglobin ranges by gestational age, identifying the prevalence of postpartum anemia, and evaluating the role of mean corpuscular volume for identifying iron deficiency.

METHODS

A retrospective review of laboratory results from 1239 pregnant women without hemoglobinopathy was performed. Measurement of hemoglobin, iron studies, and ferritin were performed with routine gestational diabetes screening. Anemia was defined as hemoglobin <110 g/L. Iron deficiency was defined as ferritin <30 μg/L and/or iron percent saturation <16%. Means and SDs or medians and IQRs were calculated, as appropriate.

RESULTS

A total of 89% (1102 of 1239) of women were iron deficient. Of the 7% (89 of 1239) who were anemic, 94% (84 of 89) were iron deficient. The mean gestational age was 26.2 (SD 2.7) weeks. The median hemoglobin was 121 g/L (IQR 10, range 92-150g/L). The median hemoglobin in the 137 iron-replete women was 124 g/L (IQR 9, range 100-147g/L). After excluding the bottom 5%, the lower limit of hemoglobin in iron-replete women was 110 g/L.

CONCLUSIONS

Iron deficiency is common in pregnancy and cannot be recognized solely by hemoglobin assessment. Iron studies should be included in routine prenatal bloodwork to identify and treat women with iron deficiency. The current threshold for defining anemia in pregnancy may be too low. Further research with more iron-replete women is needed to define hemoglobin reference ranges in pregnancy. Clinicians should recognize that a hemoglobin level below 110 g/L in pregnancy warrants investigation.