Plasma prostaglandin in pregnant women with term and preterm deliveries.

Because of the involvement of prostaglandins in the labor mechanism, it was hypothesized that elevated prostaglandin levels would presage preterm deliveries. A comparison of plasma 13,14-dihydro-15-ketoprostaglandin F2 alpha (PGFM) levels was made between pregnant patients who eventually delivered at term (N = 22) and those who delivered preterm (N = 17). Maternal blood was collected from each patient at approximately 1-week intervals between 16 and 40 weeks' gestation and during labor. Mixed cord blood was also obtained at delivery. PGFM was measured in plasma by radioimmunoassay. Plasma PGFM concentrations did not vary throughout pregnancy. PGFM concentrations did increase during labor, and the highest levels were found in cord blood at delivery. Mean PGFM levels during labor and in cord blood were not significantly different between the preterm and term groups. In 1 preterm delivery patient the PGFM concentration during labor was higher than that of all other patients, including those who delivered at term. Excluding this patient, preterm labor PGFM concentrations were significantly lower (P less than .05) than those at term. In general, the study provides evidence that most cases of preterm labor are not characterized by elevated prostaglandin levels.