The aim of this study was to investigate how maternal fish intake during pregnancy and levels of n-3 long-chain polyunsaturated fatty acids (LCPUFAs) in the infant’s cord serum correlated with different subsets of B- and T-cells in cord blood and B-cell activating factor (BAFF) in cord plasma, and with doctor-diagnosed allergy at 3 and 8 years of age in the FARMFLORA birth-cohort consisting of 65 families. Here, TNFSF13B is linked to allergic disease.