Increased concentrations of arachidonic acid lipoxygenase metabolites in amniotic fluid during parturition.

: This study was undertaken to examine whether spontaneous labor at term is associated with changes in the amniotic fluid concentrations of arachidonate lipoxygenase metabolites. Amniotic fluid was obtained from 15 women at term in active labor (with cervical dilatation of at least 6 cm) and from 15 nonlaboring control women matched for maternal age, parity, and gestational age. Cultures of amniotic fluid for bacteria and mycoplasma were negative. Products of arachidonate lipoxygenase metabolism--12-hydroxyeicosatetraenoic acid (12-HETE), 15-hydroxyeicosatetraenoic acid (15-HETE), and leukotriene B4--were measured by radioimmunoassay. The median concentrations of 12-HETE, 15-HETE, and leukotriene B4 in the amniotic fluid of nonlaboring women were 11.50 ng/mL, 0.45 ng/mL, and 21 pg/mL, respectively, and in the amniotic fluid of laboring women, 24.63 ng/mL, 4.34 ng/mL, and 96 pg/mL, respectively. The differences between labor and nonlabor amniotic fluid concentrations of all three lipoxygenase products were significant (P less than .05, Wilcoxon test). These observations are consistent with involvement of products of the lipoxygenase pathway of arachidonic acid metabolism in the mechanism of human parturition.