Background The preponderance of evidence now indicates that elevated long-chain omega-3 polyunsaturated fatty acid (LC omega-3 PUFA) intake is often associated with reduced risk of preterm birth (PTB). This conclusion is based on recent meta-analyses that include several studies that reported null findings. We probed the reasons for this heterogeneity across studies and its implications for PTB prevention using country-level data.
Methods We analysed the relationship between national PTB rates (<37 weeks of gestation) and omega-3 PUFA intake norms from 184 countries for the year 2010. To estimate the total LC omega-3 PUFA levels (eicosapentaenoic acid [EPA]/docosahexaenoic acid [DHA]) that these norms produce we utilised a metric that accounts for (1) seafood-based omega-3 intake (EPA/DHA) and (2) plant-based omega-3 intake (alpha-linolenic acid [ALA]), ~20% of which is converted to EPA/DHA in vivo. We then assessed the shape of the omega-3–PTB relationship with a penalised spline and conducted linear regression analyses within the linear sections of the relationship.
Results Penalised spline analyses indicated that PTB rates decrease linearly with increasing omega-3 levels up to ~600 mg/day. Income-adjusted linear regression analysis among the countries in this exposure range indicated that the number of PTBs per 100 live births decreases by 1.5 (95% CI 2.8 to 0.3) for each 1 SD increase in omega-3 intake norms (383 mg/day).
Conclusions Taken with prior evidence for a causal association on the individual level, our findings indicate that omega-3 PUFA deficiency may be a widespread contributing factor in PTB risk. Consideration of baseline omega-3 PUFA levels is critical in the design of future interventions.
- preterm birth
- food systems
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Contributors THC conceived of the primary study idea (based partly on prior work with SMW), conducted the analyses and drafted the manuscript. JB and SMW provided critical feedback and important analytic guidance, as well as key intellectual and writing contributions. SMW was the senior author and all authors approved the final version for submission.
Funding This work was supported in part by the March of Dimes Ohio Collaborative for the Prevention of Preterm Birth, and a National Institutes of Health grant P20 GM103534.
Disclaimer The funding sources had no involvement in the design or conduct of this research, the writing of the manuscript or the decision to submit it for publication. The depiction of boundaries on the map(s) in this article do not imply the expression of any opinion whatsoever on the part of BMJ (or any member of its group) concerning the legal status of any country, territory, jurisdiction or area or of its authorities. The map(s) are provided without any warranty of any kind, either express or implied.
Competing interests None declared.
Ethics approval This study combined and reanalysed two publically available datasets.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The study data are available in the supplement and additional data and details are available from the papers that we cited as data sources.
Patient consent for publication Not required.
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