The study in the journal Pediatrics finds it could reduce a baby's risk of asthma later in life.
Scientists say the window of protection occurs between six months and 12 months of age and that adding fish to the diet before that or not at all in the first year seems to carry an increased risk of wheezing and shortness of breath.
But not all pediatricians agree with this finding. One expert objects with feeding fish to infants because of potential harms such as developing allergies.
Authors of the study agree more studies need to be done before parents introduce any seafood to infants.