\g=a\-MSH, ACTH and \g=b\-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 \g=a\-MSH, ACTH and \g=b\-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 \g=b\-endorphin and \g=a\-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 \g=b\-endorphin and \g=a\-MSH (r=0.52) was found. In complicated pregnancies, \g=a\-MSH and ACTH concentrations were similar to those found in normal pregnancies; on the other hand, the level of \g=b\-endorphin, was found to be 130% higher than normal. As in normal pregnancies, \g=a\-MSH, ACTH and \g=b\-endorphin levels increased at labour, but only by 46, 44 and 23%, respectively. In contrast to in normal pregnancies, the correlation between \g=b\-endorphin and \g=a\-MSH or ACTH was not significantly modified by labour values. The present results confirm and extend previous studies showing that \g=b\-endorphinmay be considered a marker of fetal distress and that the fetal pituitary is capable of reacting to stressful stimuli in normal and suffering fetuses.The major pro-opiomelanocorticotropin (POMC) derivatives a-MSH, ACTH and ß-endorphin (1,2) appear at very early stages of fetal development (3,4) and are found not only in the fetal pituitary gland but also in fetal plasma and amniotic fluid (5,6). The fetal pituitary gland seems to be the major source of these peptides in fetal fluids (7,8), although they have been detected also in placenta and amniochorial membranes (9,10). It has also been shown that amniotic a-MSH and ß-endorphin decrease during pregnancy, the highest levels being found in the 1st trimester and the lowest in the 3rd trimester, whereas the ACTH concentra¬ tion was found to be lowest in the 2nd and highest in the 3rd trimester (6). Moreover a-MSH seems to play an important role in the development of the feto-placental unit (11,12) and, like ACTH, in the control of fetal steroidogenesis (13,14). Neverthe¬ less, very little is known about their physiological function in prenatal life. While it is well established that in adult life these peptides are released by stressful stimuli to coordinate biochemical, endocrinological and behavioural changes that consti¬ tute an adaptative mechanism against stress (15), few and incomplete results exist about the effect of stress on fetal plasma and amniotic concentration of POMC-derived peptides in normal pregnancies or pregnancies complicated by maternal disorders that can be associated with fetal discomfort. The only exception is for amniotic ß-endorphin, whose concentration was found to be increased in suf¬ fering fetuses (8,16,17).With the a...
