This research project will be to investigate the role of interleukin-6 in the pathophysiology of preterm labor. The hypotheses to be tested include: (1) IL-6 is produced by gestational tissues in response to infection and that IL-6 will stimulate prostaglandin production by decidua and amnion; (2) the regulation of IL-t production is mediated by other inflammatory cytokines, effectors of cell signal transduction, and steroid hormones; and (3) determination of amniotic fluid and/or serum IL-6 is a useful biochemical marker of infection-induced preterm labor. Four groups of patients will be studied: infection-induced preterm labor, idiopathic preterm labor, term labor, and term at cesarean section (not in labor). Cultured trophoblast, decidua, chorion and amnion will be used for these studies. Basal IL-6 production from these tissues will be determined using IL-6 ELISA and bioassay. The regulation of IL-6 production from selected tissues by other inflammatory cytokines, cell signal transduction agonists and antagonists, and steroid hormones will be studied. The sensitivity and specificity of amniotic fluid and serum IL-6 determination in predicting infection-induced preterm labor will also be determined.