Prepregnancy Obesity Is Not Associated with Iron Utilization during the Third Trimester

Background: An adequate maternal iron supply is crucial for maternal red blood cell (RBC) expansion, placental and fetal growth, and fetal brain development. Obese women may be at risk for poor iron status in pregnancy due to proinflammatory-driven overexpression of hepcidin leading to decreased iron bioavailability. Objective: The objective of this study was to determine the impact of prepregnancy (PP) obesity on third-trimester maternal iron utilization. Design: Using the stable isotope Fe-57, we measured iron utilization in the third trimester in PP obese IBMI (in kg/m(2)): >= 301 and nonobese (BMI: 18.5-29.9) women. We also assessed iron status, hepcidin, inflammation, erythropoietin, dietary iron intake, and gestational weight gain. Descriptive and inferential statistical tests (e.g., Student t test, Pearson correlation) were used for data analysis. Results: Fifty pregnant women (21 PP obese, 29 PP nonobese) were included. Mean age was 276 +/- 6.8 y and mean gestational age at time of Fe-57 administration was 32.7 +/- 0.7 wk. Anemia (hemoglobin <11 g/dL for non-black and <10.2 g/dL for black women) affected 38% of women (43% PP obese compared with 35% PP nonobese; P= 0.55). Women with PP obesity had significantly higher C-reactive protein (8.5 compared with 3.4 mg/L, P= 0.0007) and total body iron corrected for inflammation (6.0 compared with 4.3 mg/kg, P= 0.04) compared with the nonobese women. There was no difference in serum hepcidin or iron utilization between the PP BMI groups. Conclusion: This is the first study to assess the impact of PP obesity on maternal iron utilization. We found no difference in iron utilization in the third trimester of pregnancy in women with and without PP obesity. Despite higher frequency of anemia, women with PP obesity had less depleted body iron stores, suggesting some degree of iron sequestration. This finding should be followed up and extended to understand effects on fetal iron bioavailability.