Background : The presence of fibronectin fragments has been observed in some inflammatory diseases and is believed to reflect tissue breakdown. In this study, possible fibronectin fragmentation and alterations in its domain and sialyl and fucosyl glycotope expressions were analyzed in amniotic fluids in relation to intrauterine infection. Methods : Samples of amniotic fluid were taken from normal pregnancies and pregnancies (28 and 42 weeks) complicated by intrauterine infection. Fibronectin fragmentation was analyzed by immunoblotting. The expression of cellular, fibrin, C-terminal and EDA fibronectin domains, as well as α2,3- and α2,6-linked sialic acids, and α1,6-, α1,3- and α1,2-linked fucoses, was determined by ELISA, using domain-specific monoclonal antibodies and specific lectins, respectively. Results : Amniotic fibronectin immunoblots from pregnancies with intrauterine infection revealed three groups of results. In group 1, with the native fibronectin band, and in group 2 with bands of native fibronectin and several fibronectin fragments, only higher α1,6-linked fucose expression was observed. In the infection group 3, characterized by profound fragmentation of fibronectin, lower expression of all fibronectin domains analyzed and of α1,6-linked sialic acid and α1,2-linked fucose was found. Conclusions : Amniotic fibronectin status was found to be associated with pregnancy complicated by intrauterine infection. Such alterations could have a potential diagnostic value in the prevention of or intervention in fetal intrauterine infection. Clin Chem Lab Med 2007;45:208–14.