Correlation between amniotic levels of a-MSH, ACTH and b-endorphin in late gestation and labour in normal and complicated pregnancies

alpha-MSH, ACTH and beta-endorphin 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 alpha-MSH, ACTH and beta-endorphin 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 beta-endorphin and alpha-MSH (r = 0.92) or ACTH (r = 0.76) 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 beta-endorphin and alpha-MSH (r = 0.52) was found. In complicated pregnancies, alpha-MSH and ACTH concentrations were similar to those found in normal pregnancies: on the other hand, the level of beta-endorphin, was found to be 130% higher than normal. As in normal pregnancies, alpha-MSH, ACTH and beta-endorphin levels increased at labour, but only by 46, 44 and 23%, respectively. In contrast to in normal pregnancies, the correlation between beta-endorphin and alpha-MSH or ACTH was not significantly modified by labour values. The present results confirm and extend previous studies showing that beta-endorphin 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.