OBJECTIVES: Sialic acid is a negatively charged monosaccharide attached to non-reducing end of N- and O-linked carbohydrate chains of glycoconjugates. The claimed biological functions of sialic acid include its participation in cell to cell recognition and interaction as well as affecting the function of receptors by providing binding sites for ligand. Increased sialic acid concentration have been observed in several diseases e.g. malignancies, diabetes, inflammatory disorders, rheumatoid arthritis and alcoholism. DESIGN: The aim of the present work was to determine if the amount of sialic acid attached to glycoconjugates of amniotic fluid changes during pregnancy. MATERIALS AND METHODS: The sialic acid content in 47 samples of amniotic fluid derived from pregnant women with gestational age between 13 and 42 was studied by sialic acid specific lectins immunosorbent assay. The patient samples were divided into seven groups. RESULTS: Time dependent changes in the degree of sialylation of glycoconjugates in amniotic fluid during pregnancy, particularly in advanced pregnancy were observed. Moreover, the highest sialic acid content on glycoconjugates in pregnancies complicated by premature rupture of membranes and is prolonged pregnancy were also detected. CONCLUSIONS: Sialic acid content determination in amniotic fluid could be a potentially useful marker of inflammation process of amniochorion during pregnancy.