This study was conducted to describe the distributions of the initial decidual PRL content (D-PRL) and the decidual PRL secretion (D-PRL-s) in vitro at term and to ascertain whether the clinical data might influence these decidual PRL measures and their correlation with the amniotic fluid PRL concentration (A-PRL). Decidual tissue was obtained after 134 normal pregnancies at term. D-PRL and D-PRL-s into the medium after an 8 h incubation were determined. The distributions of D-PRL and D-PRL-s were skewed to the right. A logarithmic transformation generated symmetric distributions. Eight women who were delivered by vacuum extraction due to intra-uterine asphyxia had D-PRL values similar those in normal vaginal parturition, whereas D-PRL-s values were significantly reduced (p less than 0.02). No significant difference (p greater than 0.05) was found in the decidual PRL measures in the vaginal deliveries between those receiving labor stimulating medication and those without, or between women who gave birth vaginally and women undergoing elective cesarean section. Stepwise multiple regression analyses of data obtained from 30 women who gave birth after uncomplicated or various pathological pregnancies showed logarithmically transformed A-PRL to be closely correlated with D-PRL, and these correlations were improved by including the week of gestation as a second step (p less than 0.00001). After normal pregnancy, D-PRL-s was significantly correlated with D-PRL (p less than 0.01), and D-PRL was correlated with the week of gestation (p less than 0.05). None of the remaining clinical data improved the correlations.(ABSTRACT TRUNCATED AT 250 WORDS)