Abstract
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.
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Key Points
Preterm birth (PTB), or pregnancy lasting <37 weeks, is a common obstetrical problem associated with a number of immediate and lifelong health problems, including neonatal death, acute and chronic lung disease, brain injuries and neurodevelopmental problems. This study aimed at determining better understanding of long-chain omega-3 polyunsaturated fatty acid by assessing country-level PTB rates and dietary fat intake estimates to (1) characterize the potential worldwide impact of this dietary factor and (2) reassess conclusions drawn from the prior literature. The results suggest sufficient omega-3 intake can reduce the risk of PTB. The authors hypothesise that increasing omega-3 PUFA intake could decrease PTB rates in the 157 countries with estimated LC omega-3 PUFA levels less than 600 mg/day. The analysis of country-level omega-3 intake norms and PTB rates illuminates three critical factors that were only sporadically addressed in the prior studies: (1) baseline intake rates, (2) alternative dietary sources of LC omega-3 PUFA and (3) the possibility of a threshold for sufficient intake. The cross-sectional ecological design of this study means that it cannot provide strong evidence for a causal association on the level of the individual, but this evidence already exists, and this study provides essential contextual information.