Relative amounts of sialic acid and fucose of amniotic fluid glycoconjugates in relation to pregnancy age.

The present knowledge concerning the glycan structures and role of glycoconjugates derived from amniotic fluid is fragmentary and mainly focuses on the individual glycoproteins. The question has arisen as whether the general glycosylation pattern of amniotic fluid glycoconjugates can change with the progression of a normal pregnancy. In the present work we have described the dynamic, quantitative alterations in relative amounts of sialic acid and fucose linked by a variety of anomeric linkages to subterminal oligosaccharide structures of amniotic fluid glycoconjugates in relation to pregnancy age. The analysis was performed in the following groups of amniotic fluids derived from normal pregnancy by lectin dotting method: "2nd trimester" (14-19 weeks), "3rd trimester" (29-37 weeks), "perinatal period" (38-40 weeks) , "delivery at term" (39-41 weeks) and "post date pregnancy" (41-43 weeks). In the "3rd trimester" the amniotic fluid glycoconjugates contained higher relative amounts of glycans terminated by alpha2-6-linked sialic acid (p < 0.00002) and by alpha1-6 innermost fucose (p < 0.000001) than those in the 2nd trimester. In contrast, they showed the lower relative amount of fucose linked alpha1-3 (p < 0.02). At the perinatal period the relative amount of alpha2-6-linked sialic acid increased (p < 0.03), and it then decreased during delivery (p < 0.02) to the level found in the "3rd trimester" group. In the post date pregnancy all parameters studied increased. The sialyl- and fucosyl-glycotopes of the amniotic fluid glycoconjugates may play an critical role in growth and tissue remodeling of the foetus, as well as may might reflect maturation of a foetus. Additionally, a determination of the glycotope expressions might be helpful in prenatal diagnosis as predictor factors for well being of mother and child.