Omega-3 polyunsaturated fatty acid intake norms and preterm birth rate: a cross-sectional analysis of 184 countries

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.

Keywords: diet; food systems; omega-3; poly-unsaturated-fatty-acid; preterm birth; prevention.

Figure 1

Penalised spline modelling the omega-3–PTB relationship. (A) Country-level omega-3 intake norms among females are on the x-axis and country-level preterm birth rates are on the y-axis. Each vertical dash below the spline on the x-axis represents a single country, allowing the figure to convey data density throughout the exposure distribution. The shape of the spline is most certain in the areas of greatest data density. (B) Same as panel A except the Maldives were excluded, and the threshold is unchanged. LC omega-3 PUFA, long-chain omega-3 polyunsaturated fatty acid; PTB, preterm birth.

Figure 2

Countries with high and low dietary intake norms for omega-3 PUFAs among females. Countries with >600 mg/day LC omega-3 PUFA intake are in green, the threshold from the spline. Countries with <217 mg/day LC omega-3 PUFA are in gold; these countries are at least 1 SD (383 mg/day) below the 600 mg/day threshold. Countries with intermediate intake levels (217–600 mg/day) are in white. Country names and intake levels are listed in online supplementary table S3. LC omega-3 PUFA, long-chain omega-3 polyunsaturated fatty acid.