To assess whether timing of introduction of fish and the amount of fish consumption in infancy were associated with asthmalike symptoms at preschool age.

This study was embedded in the Generation R study (a population-based birth cohort in Rotterdam, Netherlands). At the age of 12 and 14 months, timing of introduction of fish into the infant's diet was assessed. The amount of fish consumption at 14 months was assessed by a semiquantitative food frequency questionnaire. Presence of asthmalike symptoms in the past year was assessed at the child's age of 36 and 48 months.

Relative to no introduction in the first year of life, introduction between age 6 and 12 months was significantly associated with a lower risk of wheezing at 48 months (odds ratio [OR]: 0.64; 95% CI: 0.43-0.94). When compared with introduction between 6 and 12 months, no introduction in the first year and introduction between 0 and 6 months were associated with an increased risk of wheezing at 48 months (OR: 1.57; 95% CI: 1.07-2.31 and OR: 1.53; 95% CI: 1.07-2.19, respectively). The amount of fish at age 14 months was not associated with asthmalike symptoms (P > .15).

Introduction of fish between 6 and 12 months but not fish consumption afterward is associated with a lower prevalence of wheezing. A window of exposure between the age of 6 and 12 months might exist in which fish might be associated with a reduced risk of asthma.