correlation between amniotic levels of alphamsh acth and betaendorphin in late gestation and labour in normal and complicated pregnancies alphamsh acth and betaendorphin were measured by radioimmunoassay in samples of amniotic fluid collected from the 32nd to the 38th gestational week and at labour from normal pregnancies and pregnancies complicated by gestosis in normal pregnancies the concentration of alphamsh acth and betaendorphin remained relatively constant during the last 7 gestational weeks but increased at labour above the values of the 38th week by 88 143 and 96 respectively a positive correlation between betaendorphin and alphamsh r 092 or acth r 076 levels was found when labour values were considered in the regression analysis in contrast when labour values were excluded only a poor positive correlation between betaendorphin and alphamsh r 052 was found in complicated pregnancies alphamsh and acth concentrations were similar to those found in normal pregnancies on the other hand the level of betaendorphin was found to be 130 higher than normal as in normal pregnancies alphamsh acth and betaendorphin levels increased at labour but only by 46 44 and 23 respectively in contrast to in normal pregnancies the correlation between betaendorphin and alphamsh or acth was not significantly modified by labour values the present results confirm and extend previous studies showing that betaendorphin may be considered a marker of fetal distress and that the fetal pituitary is capable of reacting to stressful stimuli in normal and suffering fetuses