The relationship of amniotic fluid cytokines and preterm delivery, amniotic fluid infection, histologic chorioamnionitis, and chorioamnion infection.

OBJECTIVE: To assess the association between cytokines in the amniotic fluid (AF) and preterm delivery, the isolation of bacteria from the AF or chorioamnion, and histologic chorioamnionitis.
METHODS: Fifty afebrile women with intact membranes in preterm labor at or before 34 weeks' gestation underwent amniocentesis. Cytokine levels were measured in AF, and cultures were performed. Placentas were cultured and examined histologically.
RESULTS: Thirty-two (64%) of the 50 patients delivered at or before 34 weeks' gestation. Delivery at or before 34 weeks, compared with delivery after 34 weeks, was related to increased levels of interleukin-6 (IL-6) (88 versus 12%; P < .001), interleukin-1 (IL-1) alpha (50 versus 6%; P = .004), IL-1 beta (42 versus 0%; P = .002), and prostaglandin (PG) E2 (66 versus 22%; P = .008). Bacteria were recovered from the AF of nine (18%) of the 50 patients. All of the cytokines with increased levels, plus tumor necrosis factor (TNF)-alpha, were related to bacteria in the AF. Increased IL-6, IL-1 alpha, IL-1 beta, TNF-alpha, and PGE2 were also associated with histologic chorioamnionitis among women who delivered within 1 week of amniocentesis. Elevated cytokine levels were not related to chorioamnion infection.
CONCLUSIONS: Elevated AF cytokines and PGE2 predicted delivery before 34 weeks' gestation and delivery within 7 days of the amniocentesis, as well as AF infection and histologic chorioamnionitis. These findings support the hypothesis that infection is one cause of preterm delivery, operating via a mechanism involving induction of cytokine production.