Prenatal consumption of omega-3 fatty acids can act as an adjuvant in the development of the immune system and affect the inflammatory response of neonates.

We conducted a double-blind, randomized, placebo-controlled trial in Cuernavaca, Mexico. We randomly assigned 1,094 pregnant women (18-35 years of age) to receive 400 mg/d of algal docosahexaenoic acid (DHA) or placebo from 18 to 22 weeks of gestation through delivery. Birth outcomes and respiratory symptoms information until 18 months were available for 869 mother-child pairs. Questionnaires were administered, and maternal blood samples were obtained at baseline. Maternal atopy was based on specific IgE levels. During follow-up, information on infants' respiratory symptoms was collected through questionnaires administered at 1, 3, 6, 9, 12, and 18 months of age. Negative binomial regression models were used to evaluate the effect of supplementation on respiratory symptoms in infants.

Among infants of atopic mothers, a statistically significant protective effect of DHA treatment was observed on phlegm with nasal discharge or nasal congestion (0.78; 95% CI, 0.60-1.02) and fever with phlegm and nasal discharge or nasal congestion (0.53; 95% CI, 0.29-0.99), adjusting for potential confounders.

Our results support the hypothesis that DHA supplementation during pregnancy may decrease the incidence of respiratory symptoms in children with a history of maternal atopy.