The purpose of this study was to determine whether preterm parturition is associated with changes in maternal plasma and amniotic fluid dehydroepian-drosterone-sulfate concentrations. A cross sectional study was constructed according to the gestational age at admission and response to tocolysis. Group 1 consisted of women admitted with preterm labor and intact membranes between 28 and 31 weeks and 6 days gestational age (n = 40). Group 2 included 40 patients with preterm labor between 32 and 36 weeks gestational age. Both groups were classified into two subgroups: preterm delivery within seven days of admission and term delivery. Commercially available immunoassay kits validated for amniotic fluid analysis of DHEA-S, were used to measure maternal plasma and amniotic fluid DHEA-S concentrations. Maternal plasma DHEA-S concentrations were significantly higher in women with preterm labor who delivered preterm than in those who delivered at term. (Group 1: median 800 ng/ml [range 100-1100] vs. median 200 ng/ml [70-800], P < 0.001; Group 2: median 850 ng/ml [300-1700] vs. median 300 ng/ml [90-1100], P < 0.001). In contrast, no significant differences were detected in amniotic fluid DHEA-S concentrations. Our data suggest that the rise in maternal plasma DHEA-S concentrations observed in patients with preterm labor may be related to the effects of stress during labor.