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Daily prenatal iron use increased birth weight
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Incremental increases in iron dosing during pregnancy yielded significant increases in birth weight, according to results of a systematic review and meta-analysis.
The researchers conducted the investigation to examine whether maternal anemia and prenatal iron use is associated with poor hematological and pregnancy outcomes among mothers. They also sought to evaluate whether iron exposure, dose and duration of use, or hemoglobin concentration during the prenatal period affected pregnancy outcomes.
Researchers used the PubMed and Embase databases to identify randomized trials of prenatal iron use and prospective cohort studies designed to investigate anemia in the prenatal setting. Cross sectional and case-control studies were excluded from the analysis.
The researchers identified 48 randomized trials involving 17,793 women, as well as 44 cohort studies that involved 1.8 million women.
Prenatal iron use increased mean hemoglobin concentration by 4.59 g/L (95% CI, 3.72-5.46), results showed. Iron use also yielded significant decreases in anemia risk (RR=0.50; 95% CI, 0.42-0.59), iron deficiency (RR=0.59; 95%CI, 0.46-0.79), iron deficiency anemia (RR=0.40; 95% CI, 0.26-0.60) and low birth weight (RR=0.81; 95% CI, 0.71-0.93).
The investigators observed no significant effect of iron on preterm birth (RR=0.84; 95% CI, 0.68-1.03).
An analysis of cohort study results showed anemia in the first or second trimester was associated with significant increases in risk for low birth weight (adjusted OR[aOR]=1.29; 95% CI, 1.09-1.53) and preterm birth (aOR=1.21; 95% CI, 1.13-1.30).
Results of an exposure-response analysis showed the relative risk for maternal anemia was 0.88 (95% CI, 0.84-0.92) for every 10 mg increase in daily iron dose up to 66 mg per day (P<.001 for linear trend).
Every 10 mg increase in dose per day increased birth weight by 15.1 g (6.0-24.2; P=.005 for linear trend) and reduced risk for low birth weight by 3% (RR=0.97; 0.95-0.98; P<.001 for linear trend).
After adjustments for dose, researchers observed no association between duration of iron use and outcomes. An additional 1 g/L increase in mean hemoglobin yielded an increase in birth weight of 14 g (6.8-21.8; P=.002 for linear trend).
“Prenatal anemia and iron deficiency have been identified as one of the preventable risk factors for disease with a substantial disease burden,” the researchers wrote. “This calls for a rigorous evaluation of the effectiveness of existing antenatal care programs in high-burden countries to identify gaps in policy and program implementation. Targeted interventions to strengthen the infrastructure of antenatal care should be used. Future research to explore feasible strategies of iron delivery in a country setting and evaluation of the effectiveness of other strategies, such as fortification and dietary diversification, should be done.”
Disclosure: The researchers report no disclosures.
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Harry S. Jacob, MD, FRCPath(Hon)
Rough calculation indicates that a daily 300-mg tablet of ferrous sulfate (60 mg of iron) would, on average, increase birth weight by approximately 1 pound in this patient cohort — an astounding finding.
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