Purpose: Current studies suggest that changes of chorioamnionitis are associated with the appearance of bronchial-associated lymphoid tissue (BALT), during fetal development. The aim of this study was to examine and analyse apart from the appearance of BALT, the expression of structural proteins in the lung parenchyma during gestation. Materials and Methods: A series of 149 paraffin-embedded human fetal lung specimens at the second trimester of development were examined by immunohistochemistry using the monoclonal antibodies CD20, CD3, Tenascin-C, Vimentin, and Fibronectin. Results: The results of this study showed that 1) BALT does not develop in fetal period and 2) BALT which develops during fetal period is probably in response to antigenic stimulation where in the present cases occurs to be changes of chorioamnionitis which decreased the expression of filaments proteins in the intermediate cells of lung parenchyma in comparison with the normal ones. Conclusion: The expressions’ pattern of intermediate filaments proteins in the lung parenchyma can be modified by the presence of chorioamnionitis in the fetal membranes.