TY - JOUR
T1 - Iron absorption during pregnancy is underestimated when iron utilization by the placenta and fetus is ignored
AU - Delaney, Katherine M.
AU - Guillet, Ronnie
AU - Pressman, Eva K.
AU - Caulfield, Laura E.
AU - Zavaleta, Nelly
AU - Abrams, Steven A.
AU - O'Brien, Kimberly O.
N1 - Funding Information:
Supported by Cornell Agricultural Experiment Station Federal Formula Funds (project no. 2006-07-160) received from the USDA National Institutes for Food and Agriculture, General Clinical Research Center grant 5M01-RR 00044 from the National Center for Research Resources (NCRR), the US NIH National Institute of Digestive and Kidney Diseases (NIDDK) grant T32-DK007158, and the Nestlé Foundation.
Funding Information:
Supported by Cornell Agricultural Experiment Station Federal Formula Funds (project no. 2006-07-160) received from the USDA National Institutes for Food and Agriculture, General Clinical Research Center grant 5M01-RR 00044 from the National Center for Research Resources (NCRR), the US NIH National Institute of Digestive and Kidney Diseases (NIDDK) grant T32-DK007158, and the Nestl? Foundation.
Publisher Copyright:
Copyright © The Author(s) on behalf of the American Society for Nutrition 2020.
PY - 2020/8/1
Y1 - 2020/8/1
N2 - Background: Maternal iron absorption during pregnancy can be evaluated using RBC incorporation of orally administered stable iron isotope. This approach underestimates true maternal absorption of iron as it does not account for absorbed iron that is transferred to the fetus or retained within the placenta. Objective: Our objective was to re-evaluate maternal iron absorption after factoring in these losses and identify factors associated with iron partitioning between the maternal, neonatal, and placental compartments. Methods: This study utilized data from stable iron isotope studies carried out in 68 women during the third trimester of pregnancy. Iron status indicators and stable iron isotopic enrichment were measured in maternal blood, umbilical cord blood, and placental tissue when available. Factors associated with iron isotope partitioning between the maternal, neonatal, and placental compartments were identified. Results: On average, true maternal absorption of iron increased by 10% (from 19% to 21%) after accounting for absorbed iron present in the newborn (P < 0.001), and further increased by 7%, (from 39% to 42%, P < 0.001) after accounting for iron retained within the placenta. On average, 2% of recovered tracer was present in the placenta and 6% was found in the newborn. Net transfer of iron to the neonate was higher in women with lower total body iron (standardized ß = -0.48, P < 0.01) and lower maternal hepcidin (standardized ß = -0.66, P < 0.01). In women carrying multiple fetuses, neonatal hepcidin explained a significant amount of observed variance in net placental transfer of absorbed iron (R = 0.95, P = 0.03). Conclusions: Maternal RBC iron incorporation of an orally ingested tracer underestimated true maternal iron absorption. The degree of underestimation was greatest in women with low body iron. Maternal hepcidin was inversely associated with maternal RBC iron utilization, whereas neonatal hepcidin explained variance in net transfer of iron to the neonatal compartment.
AB - Background: Maternal iron absorption during pregnancy can be evaluated using RBC incorporation of orally administered stable iron isotope. This approach underestimates true maternal absorption of iron as it does not account for absorbed iron that is transferred to the fetus or retained within the placenta. Objective: Our objective was to re-evaluate maternal iron absorption after factoring in these losses and identify factors associated with iron partitioning between the maternal, neonatal, and placental compartments. Methods: This study utilized data from stable iron isotope studies carried out in 68 women during the third trimester of pregnancy. Iron status indicators and stable iron isotopic enrichment were measured in maternal blood, umbilical cord blood, and placental tissue when available. Factors associated with iron isotope partitioning between the maternal, neonatal, and placental compartments were identified. Results: On average, true maternal absorption of iron increased by 10% (from 19% to 21%) after accounting for absorbed iron present in the newborn (P < 0.001), and further increased by 7%, (from 39% to 42%, P < 0.001) after accounting for iron retained within the placenta. On average, 2% of recovered tracer was present in the placenta and 6% was found in the newborn. Net transfer of iron to the neonate was higher in women with lower total body iron (standardized ß = -0.48, P < 0.01) and lower maternal hepcidin (standardized ß = -0.66, P < 0.01). In women carrying multiple fetuses, neonatal hepcidin explained a significant amount of observed variance in net placental transfer of absorbed iron (R = 0.95, P = 0.03). Conclusions: Maternal RBC iron incorporation of an orally ingested tracer underestimated true maternal iron absorption. The degree of underestimation was greatest in women with low body iron. Maternal hepcidin was inversely associated with maternal RBC iron utilization, whereas neonatal hepcidin explained variance in net transfer of iron to the neonatal compartment.
KW - Hepcidin
KW - Iron absorption
KW - Iron partitioning
KW - Newborn
KW - Pregnancy
KW - Stable isotope
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U2 - 10.1093/ajcn/nqaa155
DO - 10.1093/ajcn/nqaa155
M3 - Article
C2 - 32614379
AN - SCOPUS:85090169844
SN - 0002-9165
VL - 112
SP - 576
EP - 585
JO - American Journal of Clinical Nutrition
JF - American Journal of Clinical Nutrition
IS - 3
ER -