We showed that maternal intake of fatty fish, shellfish, and total seafood during pregnancy, as well as the cord serum levels of the fish biomarker EPA, correlate negatively with the proportions of cord blood B cells that express the marker CD5 (mainly representing very immature B cells), termed “transitional B cells”, and previously shown to be a predictor of allergy development in this cohort [19]. This evidence concerns the gene CD5 and allergic disease.