Risk of Adverse Pregnancy Outcomes: Anemia and Prenatal Iron Use

MedicalResearch.com Interview with Batool Haider, MD, MS, DSc candidate
Departments of Epidemiology and Nutrition
School of Public Health
Harvard University

Anaemia, prenatal iron use, and risk of adverse pregnancy outcomes: systematic review and meta-analysis

MedicalResearch.com: What are the main findings of the study?

Dr. Haider: The main findings of the study are that iron use in the prenatal period increased maternal mean haemoglobin concentration by 4.59 (95% confidence interval 3.72 to 5.46) g/L compared with controls and significantly reduced the risk of anaemia (relative risk 0.50, 0.42 to 0.59), iron deficiency (0.59, 0.46 to 0.79), iron deficiency anaemia (0.40, 0.26 to 0.60), and low birth weight (0.81, 0.71 to 0.93). The effect of iron on preterm birth was not significant (relative risk 0.84, 0.68 to 1.03). Analysis of cohort studies showed a significantly higher risk of low birth weight (adjusted odds ratio 1.29, 1.09 to 1.53) and preterm birth (1.21, 1.13 to 1.30) with anaemia in the first or second trimester.

Exposure-response analysis indicated that for every 10 mg increase in iron dose/day, up to 66 mg/day, the relative risk of maternal anaemia was 0.88 (0.84 to 0.92) (P for linear trend<0.001). Birth weight increased by 15.1 (6.0 to 24.2) g (P for linear trend=0.005) and risk of low birth weight decreased by 3% (relative risk 0.97, 0.95 to 0.98) for every 10 mg increase in dose/day (P for linear trend<0.001). Duration of use was not significantly associated with the outcomes after adjustment for dose. Furthermore, for each 1 g/L increase in mean haemoglobin, birth weight increased by 14.0 (6.8 to 21.8) g (P for linear trend=0.002); however, mean haemoglobin was not associated with the risk of low birth weight and preterm birth. No evidence of a significant effect on duration of gestation, small for gestational age births, and birth length was noted.

MedicalResearch.com: Were any of the findings unexpected?

Dr. Haider: The Synthesis of evidence from observational studies indicates an association between prenatal anaemia and risk of preterm birth, but evidence on other birth outcomes was inconsistent. Evidence from randomized trials on the effect of prenatal iron use on adverse birth outcomes was also inconclusive. This comprehensive meta-analysis of randomised trials suggests that prenatal iron use is associated with a significant increase in birth weight and reduction in risk of low birth weight. A dose-response relation of higher iron dose with increasing birth weight and decreasing risk of low birth weight is noted. An exposure-response relation between increasing mean haemoglobin concentration in the prenatal period and higher birth weight is demonstrated.

MedicalResearch.com: What should clinicians and patients take away from your report?

Dr. Haider: Our findings suggest that use of iron in women during pregnancy may be used as a preventive strategy to improve maternal haematological status and birth weight. Women should attend antenatal care clinics for regular monitoring of pregnancy. High quality antenatal care should be available and accessible to all women to improve the health of the mother and that of the new born.

MedicalResearch.com: What recommendations do you have for future research as a result of this study?

Dr. Haider: The findings of this study call for a rigorous evaluation of the effectiveness of existing antenatal care programmes in high burden countries to identify gaps in policy and programme 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.

Citation:

Haider BA ,Olofin I ,Wang M ,Spiegelman D ,Ezzati M ,Fawzi WW. Anaemia, prenatal iron use, and risk of adverse pregnancy outcomes: systematic review and meta-analysis. BMJ 2013;346:f3443

Updated 7/3/2012

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