Serum ferritin, soluble transferrin receptor, and total body iron for the detection of iron deficiency in early pregnancy: a multiethnic population-based study with low use of iron supplements.

BACKGROUND: Which blood-based indicator best reflects the iron status in pregnant women is unclear. Better assessments of iron status in today's multiethnic populations are needed to optimize treatment and clinical recommendations.

OBJECTIVES: We aimed to determine the prevalence of anemia (hemoglobin <11.0 g/dL in first and <10.5 g/dL in second trimester) and iron deficiency (ID) by the iron indicators serum ferritin <15 µg/L, serum soluble transferrin receptor (sTfR) >4.4 mg/L, and calculated total body iron <0 mg/kg, and their associations with ethnicity.

METHODS: This was a population-based cross-sectional study from primary antenatal care of 792 healthy women in early pregnancy in Oslo, Norway. We categorized the women into 6 ethnic groups: Western European, South Asian, Middle Eastern, Sub-Saharan African, East Asian, and Eastern European.

RESULTS: Anemia was found in 5.9% of women (Western Europeans: 1.8%; non-Western: 0-14%, P < 0.05). ID from ferritin was found in 33% (Western Europeans: 15%; non-Western: 27-55%, P < 0.05). ID from sTfR was found in 6.5% (Western Europeans: 0.3%; non-Western: 0-20%, P < 0.01). Calculated total body iron indicated ID in 11% (Western Europeans: 0.6%, non-Western: 7.0-28%, P < 0.01). The prevalence of ID was significantly higher by all measures in South Asian, Sub-Saharan African, and Middle Eastern than in Western European women, and the ethnic differences persisted after adjusting for confounders. South Asians, Sub-Saharan Africans, and Middle Easterners had lower iron concentrations by all measures for all hemoglobin intervals. Anemia related to ID varied from 35% (sTfR) to 46% (total body iron) and 72% (ferritin) depending on the iron indicator used.

CONCLUSIONS: Women at the highest risk of ID and anemia were of South Asian, Middle Eastern, and Sub-Saharan African origin. The prevalence of ID differed considerably depending on the iron indicator used.