BACKGROUND: Altered intakes of n-3 and n-6 polyunsaturated fatty acids were suggested to modulate allergic disease, but intervention trials yielded inconclusive results. Because allergies are primed in early infancy and in utero, the fetus might be more accessible to nutritional intervention strategies.

OBJECTIVE: We sought to investigate how supplementation of pregnant women with a fish oil (FO) preparation modulates allergy-related immune parameters in mothers and offspring.

METHODS: We performed a multicenter, randomized, double-blind, placebo-controlled trial. Three hundred eleven pregnant women received daily either FO with 0.5 g of docosahexaenoic acid and 0.15 g of eicosapentaenoic acid, 400 mug of methyl-tetra-hydrofolic acid, both, or placebo from the 22nd gestational week. T(H)1/T(H)2-related molecules were quantified in 197 maternal and 195 cord blood samples by using real-time RT-PCR. Data are given as geometric means [95% CIs].

RESULTS: FO supplementation was associated with increased TGF-beta mRNA in maternal (0.85 [0.8-0.89]; placebo: 0.68 [0.64-0.72]) and cord blood (0.85 [0.81-0.9]; placebo: 0.75 [0.71-0.79]). IL-1 (0.69 [0.66-0.73]; placebo: 0.83 [0.79-0.88]) and IFN-gamma (0.54 [0.51-0.57]; placebo: 0.65 [0.61-0.69]) were decreased in mothers only (P < .001). Cord blood mRNA levels of IL-4 (0.54 [0.52-0.57]; placebo: 0.64 [0.61-0.68]), IL-13 (0.61 [0.58-0.65]; placebo: 0.85 [0.80-0.89]), CCR4 (0.70 [0.67-0.73]; placebo: 0.88 [0.84-0.92]; all P < .001), and natural killer (P < .001) and CCR3+CD8+ T cells (P < .04) were decreased in the FO group.

CONCLUSION: Supplementation with FO during pregnancy is associated with decreased mRNA levels of T(H)2-related molecules in the fetus and decreased maternal inflammatory cytokines. We speculate that both effects are mediated by TGF-beta.