Amniotic fluid 6-keto-prostaglandin F1 alpha and thromboxane B2 during labor.

Production of the antiaggregatory and vasodilatory prostacyclin (prostaglandin I2) and the proaggregatory and vasoconstrictory thromboxane A2 during human labor was studied by measuring serial concentrations of the stable metabolites of these prostanoids, 6-keto-prostaglandin F1 alpha and thromboxane B2, respectively, in the amniotic fluid of 43 parturients whose labor was induced by amniotomy. The concentration of 6-keto-prostaglandin F1 alpha at amniotomy in 28 healthy parturients (92.7 +/- 12.1 pg/ml, mean +/- SE) was higher (p less than 0.02) than that in 15 preeclamptic women (48.6 +/- 5.5 pg/ml). The concentration of thromboxane B2 at amniotomy was 292.4 +/- 56.1 pg/ml, with no difference between the healthy and preeclamptic parturients. Both prostanoid levels rose consistently during labor, reaching peak levels when the cervix was fully dilated, but this rise started only after the established uterine contractility. Epidural anesthesia and paracervical blockade had no effect on 6-keto-prostaglandin F1 alpha and thromboxane B2 in the amniotic fluid, whereas oxytocin infusion was accompanied by reduced levels of thromboxane B2. The rise in amniotic fluid 6-keto-prostaglandin F1 alpha was reduced at every stage of labor in the preeclamptic women (n = 15), and its maximal increase (112.4 +/- 28.3 pg/ml) was smaller (p less than 0.005) than in the healthy women (n = 28, 240.8 +/- 21.4 pg/ml). The ratio of 6-keto-prostaglandin F1 alpha to thromboxane B2 also shifted to thromboxane B2 dominance in the preeclamptic parturients. It is concluded that a relative prostacyclin deficiency deteriorates in preeclamptic women during labor.