The adrenomedullin (AM) peptide and the expression of AM messenger RNA (mRNA) from feto-maternal tissues of 22 normotensive pregnant women and from 7 women with pregnancy-induced hypertension (PIH) during third-trimester were examined to clarify the pathophysiological features of PIH. Samples of the placenta, uterine muscle, umbilical artery, and fetal membranes were obtained from each patients under informed consent. The AM peptide was measured by a radioimmunoassay and the AM mRNA level was analyzed by Northern hybridization. The total immunoreactive AM (fmol/mg wet tissue) was significantly increased in the fetal membranes (1.95+/-0.20 vs. 3.03+/-0.44) and the umbilical artery (0.11+/-0.01 vs. 0.15+/-0.02) of the patients with PIH. On the other hand, the AM mRNA level was higher in the umbilical artery, and lower in the fetal membranes in the patients with PIH. The present results thus suggest that the changes in the expression of AM in fetal membrane and umbilical artery in PIH may play an important role in the fetal and maternal circulation.