Concentrative relationship between polymorphonuclear elastase and urinary trypsin inhibitor in amniotic fluid

In the amniotic fluid, urinary trypsin inhibitor (UTI) seems to inhibit polymorphonuclear elastase (PMNE) activity. The PMNE and UTI concentrations in normal amniotic fluid at 16–20 and 38–40 gestational weeks were measured. The PMNE concentration increased significantly at 38–40 weeks, whereas UTI concentration decreased significantly. According to concentrative relationships between both substances, PMNE may be activated more at the full term pregnancy. Since PMNE-induced tissue injury potentially causes degradation of amniotic collagen, the present result suggests that the quotient of PMNE and UTI concentrations is a reliable index to estimate the occurrence of rupture of the membranes.