Omega-3 fatty acid supplementation during pregnancy and respiratory symptoms in children.

Randomized, double-blind, placebo-controlled trial in pregnant women from Cuernavaca, Morelos, Mexico, of middle to low socioeconomic status, with offspring followed to 18 months. The active DHA arm included 429 randomized participants in the analysis.

Oral docosahexaenoic acid (DHA) from an algal source, 400 mg/day delivered as two capsules daily, given from gestational week 18 or 22 until delivery. The active intervention was compared with placebo.

Prenatal DHA was associated with fewer respiratory symptom combinations in children of atopic mothers, but not in children of nonatopic mothers. In the maternal atopy subgroup, phlegm with congestion and/or nasal discharge was reduced (IRR 0.743, 95% CI 0.633-0.871; P<0.001), fever with phlegm with congestion and/or nasal discharge was reduced (IRR 0.517, 95% CI 0.377-0.702; P<0.001), and wheezing with fever was reduced (IRR 0.432, 95% CI 0.214-0.830; P=0.007). One outcome, coughing with wheezing and/or breathing difficulty, was higher with DHA (IRR 1.263, 95% CI 1.002-1.594; P=0.042). Overall, the authors concluded that DHA supplementation during pregnancy may decrease respiratory symptoms in the most susceptible children, especially when mothers had atopy.

The apparent benefit was concentrated in a maternal-atopy subgroup, so the findings may reflect effect modification and multiple-comparison risk rather than a uniform treatment effect. Follow-up was limited to 18 months, and adverse events were not reported in the provided text. Generalizability may be limited to pregnant women in one Mexican urban setting with middle to low socioeconomic status.