Abstract
ABSTRACTBackgroundPrevious literature suggests a U-shaped relation between hemoglobin concentration and adverse birth outcomes. There is less evidence on associations between iron status and birth outcomes.ObjectiveOur objective was to determine the associations of maternal hemoglobin concentration and iron status with birth outcomes.MethodsWe conducted a secondary data analysis of data from 2 cohorts of pregnant women receiving iron-containing nutritional supplements (20–60 mg ferrous sulfate) in Ghana (n = 1137) and Malawi (n = 1243). Hemoglobin concentration and 2 markers of iron status [zinc protoporphyrin and soluble transferrin receptor (sTfR)] were measured at ≤20 weeks and 36 weeks of gestation. We used linear and Poisson regression models and birth outcomes included preterm birth (PTB), newborn stunting, low birth weight (LBW), and small-for-gestational-age.ResultsPrevalence of iron deficiency (sTfR >6.0 mg/L) at enrollment was 9% in Ghana and 20% in Malawi. In early pregnancy, iron deficiency was associated with PTB (9% compared with 17%, adjusted RR: 1.63; 95% CI: 1.14, 2.33) and stunting (15% compared with 23%, adjusted RR: 1.44; 95% CI: 1.09, 1.94) in Malawi but not Ghana, and was not associated with LBW in either country; replete iron status (sTfR <10th percentile) was associated with stunting (9% compared with 15%, adjusted RR: 1.71; 95% CI: 1.06, 2.77) in Ghana, but not PTB or LBW, and was not associated with any birth outcomes in Malawi. In late pregnancy, iron deficiency was not related to birth outcomes in either country and iron-replete status was associated with higher risk of LBW (8% compared with 16%, adjusted RR: 1.90; 95% CI: 1.17, 3.09) and stunting (6% compared with 13%, adjusted RR: 2.14; 95% CI: 1.21, 3.77) in Ghana, but was not associated with birth outcomes in Malawi.ConclusionsThe associations of low or replete iron status with birth outcomes are population specific. Research to replicate and extend these findings would be beneficial. These trials were registered at clinicaltrials.gov as NCT00970866 (Ghana) and NCT01239693 (Malawi).
Highlights
The WHO currently recommends daily supplementation with 30–60 mg/d elemental iron (+400 μg folic acid) throughout pregnancy, and in settings where anemia in pregnant women is a severe public health problem, the daily dose of 60 mg is recommended over a lower dose [1]
Iron deficiency was associated with preterm birth (PTB) (9% compared with 17%, adjusted RR: 1.63; 95% CI: 1.14, 2.33) and stunting (15% compared with 23%, adjusted RR: 1.44; 95% CI: 1.09, 1.94) in Malawi but not Ghana, and was not associated with low birth weight (LBW) in either country; replete iron status was associated with stunting (9% compared with 15%, adjusted RR: 1.71; 95% CI: 1.06, 2.77) in Ghana, but not PTB or LBW, and was not associated with any birth outcomes in Malawi
In Malawi but not in Ghana, iron deficiency and iron deficiency anemia (IDA) in early pregnancy were related to PTB and newborn stunting, and anemia in early pregnancy was related to PTB
Summary
The WHO currently recommends daily supplementation with 30–60 mg/d elemental iron (+400 μg folic acid) throughout pregnancy, and in settings where anemia in pregnant women is a severe public health problem (prevalence of ≥40%), the daily dose of 60 mg is recommended over a lower dose [1]. This amount of supplementation clearly reduces maternal iron deficiency and anemia, it is questionable whether there is a beneficial impact on birth outcomes [2] and there is concern that high maternal iron status may have a negative impact on the newborn [3]. Objective: Our objective was to determine the associations of maternal hemoglobin concentration and iron status with birth outcomes
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