Maternal use of omega-3 fatty acid supplements during pregnancy could lower the risk for asthma in offspring, a New England Journal of Medicine study finds.

Some 700 women between 22 and 26 weeks gestation were randomised to receive daily supplements containing 2.4 grams of fish oil or olive oil (placebo) until 1 week after delivery. The fish oil pill contained the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

The primary outcome — diagnosis of persistent wheeze or asthma when offspring were aged 3 to 5 years — occurred significantly less often in the fish oil versus olive oil group (17% vs. 24%). Among women with the lowest blood levels of EPA and DHA at randomisation, fish oil cut the risk for the primary outcome in half.