Bronchus‐associated lymphoid tissue consists of lymphoid follicles with or without a germinal center within the bronchial wall. Bronchus‐associated lymphoid tissue is part of the integrated mucosal immune system and present in about 50% of healthy infants. We examined a series of 141 fetal and neonatal lungs and detected bronchus‐associated lymphoid tissue in 100% of cases with amniotic infection while postpartum perinatal pneumonia did not elicit bronchus‐associated lymphoid tissue formation. Only rarely and in low density, bronchus‐associated lymphoid tissue was present in non‐infected fetuses. The in utero formation of bronchus‐associated lymphoid tissue seems to be a reactive phenomenon and – as has been shown in another study – does not portend an adverse prognosis.