The apparent protective effect of prenatal omega-3 supplements against allergic wheeze and rhinitis in babies does not endure in children beyond one year of age, Australian research suggests.

While studies have shown maternal omega-3 supplementation in pregnancy may protect offspring against allergic sensitisation, new long-term follow up data show that  the “atopic march” of progression to allergic disease continues unabated.

The findings come from analysis of the DOMInO (DHA to Optimize Mother Infant Outcome) trial, which involved almost 2400 pregnant women who were randomised to take docosahexaenoic acid-rich fish oil capsules (providing 900mg omega-3 fatty acids) or matched vegetable oil capsules prior to giving birth.

Early results from the trial showed omega-3 supplementation was associated with a reduced risk of allergic wheeze for children at one year of age (4.48% vs 8.81% for controls, adjusted relative risk 0.52).

However long term follow up has found that rates of allergic wheeze were not significantly different at three years of age (11.36% vs 11.86%) or at six years of age (13.10% vs 13.77%).

Likewise, prenatal omega-3 supplementation was not associated with any reduction in progression to allergic rhinitis symptoms at three years of age (7.65% vs 9.30% for controls, adjusted relative risk 0.83) or at six years of age (18.46% vs 21.74%, adjusted RR 0.87).

The study authors, from the South Australian Health and Medical Research Institute at Adelaide University, note that prenatal omega-3 supplementation did not have any effect on overall rates of IgE-mediated allergic disease symptoms over time

“The progression in the prevalence of parent reported allergic disease symptoms was consistent with the atopic march and increased from 17.5% at one year of age to 49.3% at 6 years of age,”they write in the World Allergy Organisation Journal.

And while prenatal omega-3 supplementation did reduce allergic sensitisation rates among infants at one year of age, this effect did not contribute much to reductions seen in house dust mite sensitisation seen at six years of age, they note.

“Although there is some evidence to suggest that maternal supplementation with 900mg [omega-3] has a protective effect on early symptoms of allergic disease and sensitisation in the offspring, we did not observe any differences in the progression of disease over time,” they conclude.

“Long term follow-up of offspring (in adolescence and adulthood) following prenatal interventions are essential to determine true effects on the trajectory of disease and to confirm whether prenatal [omega-3] supplementation may be of benefit as a primary prevention strategy,” the authors suggest.