Progesterone Metabolism and Intracellular Steroid Concentrations in Placenta, Fetal Membranes, and Myometrium before and after Labor

Department of Obstetrics and Gynecology University Hospital Innsburck, Austria
Annals of the New York Academy of Sciences (Impact Factor: 4.38). 12/2006; 595(1):440 - 446. DOI: 10.1111/j.1749-6632.1990.tb34330.x
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    ABSTRACT: Fetal oxytocin contribution to the mother during spontaneous labor was investigated using a specific and sensitive radioimmunoassay to measure oxytocin in blood, amniotic fluid, and urine. In 26 subjects with spontaneous labor and vaginal delivery (Group I) and 18 subjects with cesarean section after labor (Group II), umbilical arterial plasma (UA) oxytocin concentrations were significantly higher than umbilical venous plasma (UV) ocytocin concentrations. With elective cesarean section (Group III), UA oxytocin concentration was 29.8 +/- 7.5 pg/ml and UV oxytocin concentration was 16.1 +/- 5.9 pg/ml (n = 14). In contrast, the mean UV oxytocin concentration was higher than the mean UA oxytocin concentration, when oxytocin was given to the mothen concentration in Groups I and II was significantly higher than in Group III. Amniotic fluid oxytocin concentrations in Group I and II patients were higher than in Group III. Oxytocin was also present in fetal urine. The findings indicate that during spontaneous labor, oxytocin is produced by the fetus and flows toward the maternal circulation.
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    ABSTRACT: The influence of artificial rupture of the membranes on plasma levels of 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) and oxytocin was examined in 23 pregnant women at term. Serial blood samples were collected before and 15 minutes, 2 hours, 5 hours, and 8 hours after artificial rupture of the membranes. A significant rise in the concentration of plasma PGFM was observed at 15 minutes in the majority of women (20 of 23), but the magnitude of this early rise or the lack thereof was not related to the subsequent course of labor. The concentration of plasma PGFM at 2 hours was, on the other hand, significantly correlated with the induction-delivery interval. Amniotomy, by itself, induced labor and delivery when the increased PGFM levels were maintained from 2 to 5 hours after the procedure (n = 16). In those cases where Pitocin stimulation was required for adequate uterine contractions, it was found that plasma PGFM levels had declined to initial values at 2 hours. Pitocin infusions then partially reversed this decline. In one patient, the cervix failed to dilate in spite of prolonged Pitocin infusion which did not induce significant uterine contractions, and the infusion did not reverse the marked fall in plasma PGFM after the early but transient rise. Mean plasma oxytocin levels did not rise significantly during labor induced by artificial rupture of the membranes and were, on the average, similar to the levels observed during the first stage of spontaneous or oxytocin-induced labor. Considering the previously demonstrated maximal levels of uterine oxytocin receptors in early labor, the absence of a rise in the plasma oxytocin levels does not negate a role for oxytocin in working synergistically with prostaglandins in the mechanism of labor.
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