['Interleukin-6 (IL-6) increases in culture-positive amniotic fluid in women with preterm labor. IL-6 stimulates the production of prostaglandins leading to increased uterine activity.', 'We tested the hypothesis that IL-6 increases myometrial activity through release of uterotonic mediators. We studied the effect of IL-6 on uterine contractions in the absence and presence of fetal membranes to determine if the effect was on myometrium alone or was mediated through fetal membranes/decidua. IL-6 in concentrations of 100, 10, 0.1 or 0 ng/ml was added to the maternal side of the dual chamber-fetal membrane-uterine muscle in vitro model.', 'We found that 10 ng/ml of IL-6 alone, without fetal membranes, caused a significant decrease in uterine contractions over time (P < or = 0.01). This decrease was not observed with the addition of term, nonlabored fetal membranes.'] Does interleukin-6 stimulate rat myometrial contractions in an in vitro model?