Meta-analysisindependent cross-checkabstract checked I-SUP-102 standard review

Anaemia and iron in pregnancy: meta-analysis

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

Overview

Haider BA et al.. BMJ 2013 · PMID 23794316 · DOI 10.1136/bmj.f3443

Iron tablets halved anaemia in pregnancy, and anaemia early in pregnancy was linked to more low-birthweight and preterm babies.

Does the study support the specific claim? No · Methodological quality: moderate

Study explained simply

What did the researchers want to find out?: To link anaemia and iron use in pregnancy with outcomes for mother and baby.
How was the study done?: Meta-analysis of 48 trials and 44 cohort studies.
How many people, animals or samples were studied?: 17,793 women in trials; 1.85 million in cohorts.
What was actually found?: Iron reduced anaemia and low birthweight; anaemic mothers had more small and preterm babies.
How large was the observed effect?: Anaemia RR 0.50; low birthweight RR 0.81; anaemia-low birthweight OR 1.29.
What do the results mean in everyday life?: Anaemia in pregnancy is not harmless, and iron corrects it.
What are the study's limitations?: Older search; cohort data observational.
What does it say about Elawady's specific claim?: Contradicts refusing iron to anaemic pregnant women.
Do the results apply to Germany and Europe?: Applicable.
What can explicitly not be concluded from this study?: Cannot show that anaemia itself causes preterm birth.

Authors: Haider BA et al.
Journal: BMJ
Year: 2013
Identifier: PMID 23794316 DOI 10.1136/bmj.f3443 · PMC3689887
Verification: verified – PubMed efetch 2026-10-26; Crossref works API 2026-10-26
Retracted: no
Corrections: none
Extent checked: abstract only
Conflicts of interest and funding: COI statement in record: Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that migh

Associations of maternal anaemia and prenatal iron use with haematological and pregnancy outcomes; dose-response relations.

Study design: Meta-analysis – Systematic review and meta-analysis of randomised trials (prenatal iron) and prospective cohorts (anaemia)
Population: Pregnant women
Country: Multinational
Period: Studies published up to May 2012
Sample size: 48 RCTs (17,793 women) and 44 cohorts (1,851,682 women)
Inclusion and exclusion criteria: RCTs of prenatal iron; prospective cohorts of prenatal anaemia; cross-sectional and case-control studies excluded

Exposure / intervention: Prenatal iron (RCTs); maternal anaemia (cohorts)
Comparator: No iron/placebo; non-anaemic women
Endpoints: Haemoglobin, anaemia, iron deficiency, low birthweight, preterm birth
Statistical methods: Random-effects meta-analysis; dose-response meta-regression

Results: Iron increased haemoglobin by 4.59 g/L (3.72-5.46); anaemia RR 0.50 (0.42-0.59); iron deficiency RR 0.59 (0.46-0.79); iron-deficiency anaemia RR 0.40 (0.26-0.60); low birthweight RR 0.81 (0.71-0.93); preterm birth RR 0.84 (0.68-1.03, n.s.). Cohorts: anaemia in first or second trimester associated with low birthweight (adjusted OR 1.29, 1.09-1.53) and preterm birth (1.21, 1.13-1.30). Per 10 mg/day more iron (up to 66 mg): anaemia RR 0.88 (0.84-0.92); birthweight +15.1 g (6.0-24.2).
Absolute risks: not reported in abstract
Authors' conclusion: Daily prenatal use of iron substantially improved birth weight in a linear dose-response fashion, probably leading to a reduction in risk of low birth weight.

Trial results overlap with I-SUP-101 and are not independent confirmation; the dose-response gradient adds plausibility.

Shows that anaemia in early pregnancy is associated with worse birth outcomes and that iron improves haematological status with a dose-response.

Preterm-birth effect not significant.

Applicable.

Supports treating/preventing anaemia in pregnancy; overlapping with Cochrane evidence.

Multidimensional assessment
Multidimensional assessment
Authenticity of the source	verified
Methodological quality	moderate
Risk of bias	some concerns
Precision of results	high
Directness	direct
Reproducibility	replicated
Consistency with the overall evidence	consistent
Regional transferability	high
Adequacy of the interpretation (by the archive)	not applicable

Causal role of anaemia per se versus its causes.