Objective: To investigate the role of cytokines in normal term and preterm labor in the absence of intrauterine infection.
Methods: Cytokine (interleukin [IL]-1 beta, IL-6 and tumor necrosis factor-alpha [TNF-alpha]) release was estimated from placental and decidual cell cultures from 22 nonlaboring women at term with cesarean deliveries, 18 women with spontaneous labor at term, and 21 women with preterm labor (19-36 weeks gestation) who delivered vaginally or by cesarean, according to gestational age. Eight of 21 women delivering preterm had clinical evidence of intrauterine infection, and 13 were not infected.
Results: Placental cell cultures obtained from women with spontaneous term labor released significantly larger amounts of cytokines (median: IL-1 beta 6450 pg/mL, IL-6 1821 ng/mL, and TNF-alpha 13,506 pg/mL) compared with placental cell cultures from nonlaboring women at term (median: IL-1 beta 2602 pg/mL, IL-6 993 ng/mL, TNF-alpha 3475 pg/mL; P < .02). Placental cells from women delivering preterm with intrauterine infection did not produce significantly different amounts of cytokines (median: IL-1 beta 3929 pg/mL, IL-6 1084 ng/mL, TNF-alpha 2847 pg/mL) when compared with those of nonlaboring women at term, whereas placental cells from uninfected women delivering preterm produced significantly larger amounts of cytokines (median: IL-1 beta 22,903 pg/mL, IL-6 1899 ng/mL, TNF-alpha 15,005 pg/mL; P < .01) than cells from nonlaboring women at term. Cytokine release from decidual cell cultures was similar in all groups tested.
Conclusion: In the absence of intrauterine infection, preterm labor was associated with elevated placental cytokine release.