Meta-analysisindependent cross-checkabstract checked I-SUP-104 standard review
Iron for pregnant women who are not anaemic
The benefits and harms of oral iron supplementation in non-anaemic pregnant women: a systematic review and meta-analysis.
Overview
Watt A et al.. Fam Pract 2025 · PMID 39834271 · DOI 10.1093/fampra/cmae079
Iron tablets halved the risk of becoming anaemic (1 in 10 women helped), but did not change birthweight or preterm birth in women who started without anaemia.
Does the study support the specific claim? Partly · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
To weigh benefits and harms of routine iron in non-anaemic pregnancy.
- How was the study done?
Systematic review and meta-analysis.
- How many people, animals or samples were studied?
23 studies, 4,492 women.
- What was actually found?
Less anaemia; no effect on birth outcomes; harms poorly reported.
- How large was the observed effect?
Anaemia RR 0.50 (0.34-0.74), NNT 10.
- What do the results mean in everyday life?
Iron helps prevent anaemia even in women who start with normal blood counts.
- What are the study's limitations?
Small studies; harms data weak.
- What does it say about Elawady's specific claim?
Contradicts a ban on iron; partly supports that not every outcome improves.
- Do the results apply to Germany and Europe?
Applicable.
- What can explicitly not be concluded from this study?
Cannot settle whether all pregnant women should take iron.
Scientific in-depth review
1. Full reference
- Authors
- Watt A et al.
- Journal
- Fam Pract
- Year
- 2025
- Identifier
- PMID 39834271 DOI 10.1093/fampra/cmae079 · PMC11747145
- 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: A.P. receives funding from the National Institute for Health and Care Research (NIHR) School for Primary Care Research for research unrelated to this study. All other authors declare no conflicts of interest.
2. Research question
Benefits and harms of routine oral iron supplementation in non-anaemic pregnant women.
3. Study design and population
- Study design
- Meta-analysis – Systematic review and meta-analysis of RCTs and observational studies
- Population
Non-anaemic pregnant women
- Country
Multinational
- Period
Search date not stated in abstract
- Sample size
23 studies; 4,492 women
- Inclusion and exclusion criteria
RCTs and observational studies comparing oral iron with placebo/no supplement in non-anaemic pregnant women
4. Methods and endpoints
- Exposure / intervention
Oral iron
- Comparator
Placebo or no supplement
- Endpoints
Haemoglobin, ferritin, anaemia, birthweight, preterm birth, caesarean section, harms
- Statistical methods
Meta-analysis with GRADE certainty
5. Actual results
- Results
Haemoglobin +6.95 g/L (4.81-9.09; moderate certainty; I2 91%); ferritin +12.22 ng/mL (6.92-17.52); anaemia RR 0.50 (0.34-0.74; high certainty; I2 42%; NNT 10). No difference in birthweight, preterm birth or caesarean section. Harms inconsistently reported; insufficient evidence for any negative outcome.
- Absolute risks
NNT 10 to prevent one case of anaemia (implied control risk about 20%; stats/C-SUP-10_folate_iron.py)
- Authors' conclusion
Prophylactic iron likely results in a large reduction in maternal anaemia; evidence on harms in non-anaemic women is poor and inconsistent.
6. Strengths
- Focus on the population where guidelines disagree
- GRADE ratings
7. Weaknesses
- Small total sample
- High heterogeneity for haemoglobin
- Harms poorly studied
8. Risk of bias
- Orienting tool
- AMSTAR 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Abstract only.
9. Assessment of the statistical interpretation
RR 0.50 with NNT 10 is internally consistent with a control anaemia risk of about 20%.
10. Relevance to the specific claim
Even in non-anaemic pregnant women iron prevents anaemia; it also shows the open question of routine use (part of the 'not everyone needs supplements' argument).
11. Independent contrary findings
No effect on birth outcomes in non-anaemic women; harms under-reported.
12. Transferability to Germany and Europe
Relevant to the debate between WHO (universal) and some European guidelines (selective).
13. Overall methodological judgement
Supports the benefit of iron on maternal anaemia; leaves routine use in iron-replete women debated.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | moderate |
| Directness | direct |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Harms such as gastrointestinal effects and iron overload.
15. Linked fact checks
- There is no such thing as iron supplements: they are forbidden even for a pregnant woman with anaemia, because a diet that needs supplements is deficient. – Studies contradicting or limiting the claim