Prenatal Fish Oil Supplementation and Allergy: 6-Year Follow-up of a Randomized Controlled Trial

Randomized controlled trial with 6-year follow-up of children born to mothers with a family history of allergic disease. In the active n-3 LCPUFA arm, 368 participants were randomized and 367 were analyzed; mothers were recruited from antenatal clinics in South Australia, and all children had at least 1 first-degree relative with medically diagnosed allergic disease.

Pregnant participants in the active arm received oral capsules containing 500 mg of fish oil concentrate, providing approximately 800 mg/day DHA and 100 mg/day EPA, taken daily from 21 weeks' gestation until delivery. The comparator was vegetable oil capsules.

Prenatal n-3 LCPUFA supplementation did not reduce overall IgE-associated allergic disease at age 6. The primary composite outcome was essentially identical between groups: 116/367 (31.48%) in the n-3 LCPUFA group versus 106/336 (31.46%) in control, aRR 1.04 (95% CI 0.82-1.33; P = .73). House dust mite sensitization was lower in the supplemented group, 49 (13.42%) versus 68 (20.30%), aRR 0.67 (95% CI 0.44-1.00; P = .0495), but eczema, wheeze, rhinitis, rhino-conjunctivitis, asthma, and hayfever outcomes were not significantly different. The authors concluded that prenatal n-3 LCPUFA did not lower the overall incidence of IgE-associated allergic disease despite a possible reduction in house dust mite sensitization.

The main clinical outcome was negative, and the positive house dust mite finding was secondary and borderline significant. Results come from a familial-allergy-risk cohort in South Australia, which may limit generalizability, and the follow-up analyzed slightly fewer participants than were randomized. Multiple allergy outcomes increase the chance of chance findings.