Effects of nutrition interventions during pregnancy on low birth weight: an overview of systematic reviews

BMJ Global Health

Sep 2017

DOI: 10.1136/bmjgh-2017-000389

Citations:120

Influential Citations:4

Systematic Reviews / Meta-Analyses

Enhanced Details

Methods

Overview of 23 systematic reviews of randomized or quasi-randomized trials assessing nutrition-specific and nutrition-sensitive interventions before or during pregnancy to reduce low birth weight (LBW). Participants were pregnant women with singleton pregnancies, including low- and high-risk groups. Study designs included randomized controlled trials and quasi-RCTs. Geographic settings spanned multiple income levels. Methodological quality was assessed with AMSTAR (16 high, 6 moderate, 1 low).

Intervention

Regimens included vitamins, minerals, MMN, protein and marine oil supplements with variable dosages and timing: Vitamin A 3000–600,000 IU (daily or weekly) started mainly in the second trimester; Vitamin C ~1000 mg daily (range 100–2000 mg); Vitamin E ~400 IU daily (range 100–800 IU); Folic acid 0.4–4.0 mg daily (periconception through early pregnancy); Calcium 1.0–2.0 g daily (high-dose ≥1 g/day reduces PTB; low-dose <1 g/day reduces LBW); Iron 9–900 mg daily; Iodine 75–300 μg daily; Magnesium 64–1000 mg daily (commonly 365 mg); Zinc 5–44 mg daily (90 mg in one trial); MMN via UNIMMAP formulations (~1 RDA daily; iron 30–60 mg in some formulations); Protein supplementation: balanced energy/protein 118–1017 kcal/day and 6–44 g protein; High-protein supplementation: 40 g daily; Marine oil/long-chain n-3 fatty acids: 2.7 g daily (EPA+DHA); Start times/durations varied by regimen; Non-supplement strategies (educational or policy-level) not included here as intervention regimens.

Results

Six interventions reduced LBW: vitamin A (with other micronutrients) and low-dose calcium, zinc, MMN, nutritional education, and preventive antimalarials. MMN reduced LBW by about 11–14% and SGA by 10–17%; balanced protein/energy reduced SGA by ~21%, while high-protein increased SGA by ~58%. High-dose calcium (≥1 g/day) reduced PTB by ~24%; low-dose calcium (<1 g/day) reduced LBW by ~80% (from two small trials). Vitamin A alone did not reduce LBW/PTB; Vitamin A with iron/folate reduced LBW by ~33% in HIV-positive women. Iron alone showed no LBW effect; zinc reduced PTB by ~14% (and adolescent-pregnancy LBW by ~61% in that subgroup). Preventive antimalarials reduced LBW by ~27%. Overall, improving maternal nutrition positively affects LBW, SGA and PTB; MMN and preventive antimalarials may be considered for policy, but many effects derive from few trials with heterogeneity; more high-quality trials are needed to strengthen guidance.

Limitations

Evidence for many interventions derives from small numbers of trials; heterogeneity in regimens and populations; subgroup analyses limited; most data come from low- and middle-income countries; limited data on ELBW; some positive findings pertain to HIV-positive or adolescent subgroups; not all trials consistently reported LBW; evidence largely predated 2015 and varied in quality across reviews.

Abstract

Introduction Low birth weight (LBW, birth weight less than 2500 g) is associated with infant mortality and childhood morbidity. Poor maternal nutritional status is one of several contributing factors to LBW. We systematically reviewed the evidence for nutrition-specific (addressing the immediate determinants of nutrition) and nutrition-sensitive (addressing the underlying cause of undernutrition) interventions to reduce the risk of LBW and/or its components: preterm birth (PTB) and small-for-gestational age (SGA). Methods We conducted a comprehensive literature search in MEDLINE, EMBASE, CINAHL and the Cochrane Database of Systematic Reviews (September 2015). Systematic reviews of randomised controlled trials focusing on nutritional interventions before and during pregnancy to reduce LBW and its components were eligible for inclusion into the overview review. We assessed the methodological quality of the included reviews using A Measurement Tool to Assess Reviews (AMSTAR), PROSPERO: CRD42015024814. Results We included 23 systematic reviews which comprised 34 comparisons. Sixteen reviews were of high methodological quality, six of moderate and only one review of low quality. Six interventions were associated with a decreased risk of LBW: oral supplementation with (1) vitamin A, (2) low-dose calcium, (3) zinc, (4) multiple micronutrients (MMN), nutritional education and provision of preventive antimalarials. MMN and balanced protein/energy supplementation had a positive effect on SGA, while high protein supplementation increased the risk of SGA. High-dose calcium, zinc or long-chain n-3 fatty acid supplementation and nutritional education decreased the risk of PTB. Conclusion Improving women’s nutritional status positively affected LBW, SGA and PTB. Based on current evidence, especially MMN supplementation and preventive antimalarial drugs during pregnancy may be considered for policy and practice. However, for most interventions evidence was derived from a small number of trials and/or participants. There is a need to further explore the evidence of nutrition-specific and nutrition-sensitive interventions in order to reach the WHO’s goal of a 30% reduction in the global rate of LBW by 2025. show less