Amniotic fluid prostanoid concentrations increase early during the course of spontaneous labor at term

The purpose of this study was to determine whether amniotic fluid concentrations of prostanoids increase during spontaneous labor at term.

Amniotic fluid was retrieved transabdominally from 168 patients in spontaneous labor and from 82 patients not in labor. Prostaglandin E2, prostaglandin F2 alpha, 13, 14-dihydro-15-keto-prostaglandin F2 alpha, thromboxane B2, and 6-keto-prostaglandin F1 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.

(1) Amniotic fluid concentrations of all prostanoids were significantly higher in patients in early labor (cervical dilatation of < or = 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 F2 alpha and 13,14-dihydro-15-keto-prostaglandin F2 alpha than for prostaglandin E2, thromboxane B2, and 6-keto-prostaglandin F1 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 < or = 3 cm). (4) A significant increase in amniotic fluid concentrations of prostaglandin F2 alpha and 13,14-dihydro-15-keto-prostaglandin F2 alpha was found in patients with advanced cervical dilatation (8 to 10 cm) in comparison with those in early labor (< 3 cm).

Amniotic fluid prostanoid concentrations increase early during the course of spontaneous labor at term.