The role of chorioamnionitis and prostaglandins in preterm labor.

Spontaneous preterm labor remains a significant cause of high morbidity and mortality in the newborn. Chorioamnionitis with an associated rise in prostaglandins (PGs) is thought to be one of the factors responsible for the onset of preterm labor. In this study, 52 placentas and membranes from gestations of 35 weeks' or fewer were collected. Tissue samples of membranes and placentas were incubated in pseudoamniotic fluid, and the levels of PGs and leukotriene B4 were assayed. Swallowed amniotic fluid aspirated from the infants' stomachs was analyzed for PGs and examined microscopically for the presence of degenerate neutrophilic polymorphonuclear leukocytes (pus cells) and bacterial organisms. Prostaglandins E and F and leukotriene B4 production were significantly higher in the membranes and placentas with chorioamnionitis than in those without. Although the comparison of PG levels in the gastric fluid of infants with and without chorioamnionitis did not reach statistical significance, there was a trend toward higher levels of PGs with chorioamnionitis. Prostaglandin E levels from membranes and placentas and PGF from placentas were significantly elevated in the gastric fluid of infants with pus cells and organisms. These findings support the hypothesis that chorioamnionitis may initiate preterm labor.