Objective: To study the role of adrenomedullin(ADM) in normal early pregnancy. Methods: Plasma concentrations of ADM were measured in 30 normal early pregnancy and 10 non-pregnant women by radioimmunoassay. The expression of ADM?ADM mRNA and ADMR mRNA in villus of normal early pregnancy were determined by immunohistochemistry and in situ hybridization respectively. Results: The plasma concentration of ADM in normal early pregnancy was significantly higher than that of normal non-pregnant women (P