AMNIOTIC-FLUID PROSTANOID CONCENTRATIONS INCREASE EARLY DURING THE COURSE OF SPONTANEOUS LABOR AT TERM

OBJECTIVE: The purpose of this study was to determine whether amniotic fluid concentrations of prostanoids increase during spontaneous labor at term. STUDY DESIGN: Amniotic fluid was retrieved transabdominally from 168 patients in spontaneous labor and from 82 patients not in labor. Prostaglandin E(2), prostaglandin F-2 alpha, 13, 14-dihydro-15-keto-prostaglandin F-2 alpha, thromboxane B-2, and 6-keto-prostaglandin F-1 alpha concentrations were measured with sensitive and specific radioimmunoassays previously validated for amniotic fluid. Statistical analysis was conducted with Kruskal-Wallis analysis of variance, followed by Dunn's test for multiple comparisons. RESULTS: (1) Amniotic fluid concentrations of all prostanoids were significantly higher in patients in early labor (cervical dilatation of less than or equal to 3 cm) than in patients not in labor. (2) The magnitude of the increase in amniotic fluid prostanoid concentrations during early labor was significantly greater for prostaglandin F-2 alpha and 13, 14 dihydro-15-keto-prostaglandin F-2 alpha than for prostaglandin E(2), thromboxane B-2, and 6-keto-prostaglandin F-1 alpha. (3) Patients in the active phase of labor with cervical dilatations between 4 and 7 cm did not have higher prostanoid concentrations than those in early labor (cervical dilatation of less than or equal to 3 cm). (4) A significant increase in amniotic fluid concentrations of prostaglandin F2 alpha and 13,14-dihydro-15-keto-prostaglandin F-2 alpha, was found in patients with advanced cervical dilatation (8 to 10 cm) in comparison with those in early labor (<3 cm). CONCLUSION: Amniotic fluid prostanoid concentrations increase early during the course of spontaneous labor at term.